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Physical stem-end treatment effects on cut rose and acacia vase life and water relations
Postharvest Biology and Technology 59 (2011) 258–264
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Physical stem-end treatment effects on cut rose and acacia vase life and water relations Iftikhar Ahmad a,b,∗ , Daryl C. Joyce b , John D. Faragher b a b
Institute of Horticultural Sciences, University of Agriculture, Faisalabad 38040, Pakistan The University of Queensland, Centre for Native Floriculture, School of Land, Crop and Food Sciences, Gatton, QLD 4343, Australia
a r t i c l e
i n f o
Article history: Received 11 May 2010 Accepted 1 November 2010 Keywords: Bark removal Hot water scalding Relative fresh weight Rose Stem-end splitting Stem-end crushing Vase solution uptake Vase life Water relations Wattle
a b s t r a c t Cut Rosa hybrida cv. High & Mighty flowers and Acacia holosericea (Velvet Leaf Wattle) foliage were subjected to various physical stem-end treatments as practised by florists. Their effects on longevity (vase life) and water relations [relative fresh weight (RFW) and vase solution uptake (VSU)] were quantified. All vase water contained sodium dichloroisocyanurate (DICA) biocide. Bark removal had either positive or neutral effects on the vase life of fresh-cut rose and had either neutral or negative effects on fresh-cut acacia. Stem-end splitting had either no or negative effects on the vase life of fresh-cut rose and acacia. However, both bark removal and stem-end splitting increased the vase life of both species when applied after short term storage for 24 h at 4 ◦ C. Crushing stems had no effect on the vase life of fresh-cut rose, but tends to increase the vase life of fresh-cut acacia. Hot water scalding either increased or had no effect on the vase lives of rose and acacia. The tendency for bark removal to increase vase life of fresh-cut rose was associated with better maintenance of RFW and sustained VSU. However, for the most part, stem-end treatments had typically negative or neutral effects on RFW of fresh-cut rose and acacia. Likewise, the treatments had mostly negative or neutral effects on VSU. Overall for both species, there is little or no benefit and potentially negative effects on vase life, RFW and VSU of applying stem-end treatments as sometimes advocated by florists. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Cut flowers and foliage can have limited commercial value because they dehydrate during vase life as a result of decreased water uptake. This is true for cut rose flowers (van Doorn, 1997) and cut acacia foliage (Horlock et al., 2000; Williamson et al., 2002; Damunupola, 2009). In cut roses, water stress caused by xylem vessel blockage is a major cause of vase life termination due to premature petal wilting, lack of proper flower opening, wilting of foliage and/or bending of the pedicel (‘bent neck’) (van Doorn and Perik, 1990; Knee, 2000). In the case of Acacia holosericea (Velvet Leaf Wattle) foliage, a very short vase life of 4–7 d limits its commercial potential. Insufficient water uptake due to possible stem-end occlusion leads to early phyllode (leaf) wilting and desiccation in this otherwise promising Australian native cut foliage crop (Damunupola et al., 2010). Cut flowers and foliage develop water deficit even when placed in water (Halevy and Mayak, 1981; van Doorn, 1997). A negative
∗ Corresponding author at: Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Punjab 38040, Pakistan. Tel.: +92 333 841 7286; fax: +92 41 920 1085. E-mail address: [email protected] (I. Ahmad). 0925-5214/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2010.11.001
water balance develops when transpiration is greater than uptake (Halevy et al., 1978). Impaired water uptake is typically caused by cut stem occlusions due to microbial, physiological and physical plugging of xylem vessels (e.g. Nijsse et al., 2000; van Doorn and Cruz, 2000). Resistance to water flow in cut rose stems rises markedly soon after they are harvested (Evans et al., 1996). Numerous studies have demonstrated positive effects of various chemical additives (e.g. biocides, surfactants, ethylene inhibitors, wound healing enzyme inhibitors) on the postharvest water relations and longevity of cut flowers (e.g. de Stigter, 1980; Jones et al., 1993; van Doorn et al., 1993). However, despite anecdotal evidence of positive effects (Milner, 2009), improving postharvest water relations of cut flowers and foliage by various physical stem-end treatments is little researched. There has been research into bark removal at the base of cut rose stems to increase water uptake (de Stigter and Broekhuysen, 1986). This physical treatment effected increased water uptake and a 25% increase in FW compared with the control. Florists sometimes advocate splitting or crushing stems and also removing bark at the base of the stem to increase water uptake and extend vase life (Jones, 2001; Milner, 2009). These practices are thought to increase exposure of the vasculature to vase solution. Dipping of stem-ends into scalding (almost boiling) water is also recommended in some cases. This is particularly so for stems which contain latex with
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a view to preventing it from exuding and blocking xylem vessels (Jones, 2001). However, scalding might also sterilize stem-ends and/or destroy enzymes that otherwise lead to blockages in water uptake. Dipping of the base of Thryptomene calycina stems into 100 ◦ C water for 1 min markedly increased vase life (Jones et al., 1993). On the other hand, physical treatments are likely to damage xylem vessels, allow ingress of microbes and increase nutrient supply for microbes, which occlude stems (Jones, 2001). Other possible side effects of wounding tissues include stimulated defence-related enzyme activity and gene expression; e.g. peroxidase (Kawaoka et al., 1994) and ACC oxidase (Peck-Scott and Kende, 1999). These responses lead to biosynthesis of suberin, lignin and other wound healing compounds (Negrel et al., 1993; Moehs et al., 1996), including deposition of mucilage and tylose formation (Weiner and Liese, 1995) along with deposition of gums in the lumen of xylem conduits (Davies et al., 1981). Production of such compounds in nature serves, by xylem occlusion, to reduce entrance of microbes into damaged tissues (Bucciarelli et al., 1998). Wounding may also stimulate ethylene production (Ciardi and Klee, 2001) and promote senescence (Abeles et al., 1992) and abscission (Rapaka et al., 2007). In addition to improving water uptake, other approaches to maintaining a positive postharvest water balance for cut flowers and foliage include minimising water loss though reduction in leaf area, keeping them in an environment conducive to less water loss (viz. low temperature and high RH) and providing compatible osmotica (e.g. sucrose) in vase and/or pulsing solutions (Halevy and Mayak, 1981; Jones et al., 1993; van Doorn, 1997). The current experiments compared various physical stem-end treatments as used by florists (i.e. bark removal, stem-end splitting, stem-end crushing and hot water scalding) with the aim to improve the postharvest water relations of cut rose and acacia. It was hypothesised that the various physical stem-end treatments would improve water uptake by presenting a larger surface area of stem xylem conduits to increase direct and indirect access of water. 2. Materials and methods 2.1. Plant materials Cut stems of rose (Rosa hybrida L. ‘High & Mighty’) harvested when petals were about to reflex (Ichimura and Ueyama, 1998) and Velvet Leaf Wattle (A. holosericea A. Cunn. ex G. Don; Elliot and Jones, 1982) foliage were obtained from greenhouse and field plantings, respectively, at Karalee (152◦ 50 E, 27◦ 32 S), Queensland, Australia. They were transported to the University of Queensland, Gatton postharvest laboratory within 2 h of harvest. Harvests were conducted between 0600 and 0800 h serially from April to July (late autumn to early spring). Stems were harvested with clean sharp secateurs and placed into buckets of deionised water (DI), covered with polyethylene film and transported. Stems of rose and acacia were ca. 50 cm in length. Stem-ends were dipped into 80% (v/v) ethanol solution for 2–3 s for surface disinfection, rinsed with DI and re-trimmed under DI to remove stem-end air emboli. Resultant stem lengths were ca. 40 cm bearing the three upper leaves for roses and four phyllodes for acacia. 2.2. Experiment design and treatments Six experiments were conducted in a vase life evaluation room maintained at ca. 20 ± 2 ◦ C and 80 ± 20% relative humidity under a PAR flux of 8–12 mol m−2 s−1 from white fluorescent tubes at flower level on a daily 12 h photoperiod and under 0.2–0.4 m s−1 air speed. In each experiment, stems were placed individually into 350 mL plastic vases containing DI with 10 mg L−1 available chlo-
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rine as sodium dichloroisocyanurate (DICA; Joyce et al., 2000). Low-density polyethylene film was used to cover the mouth of each vase to limit entrance of dust and foreign objects (e.g. dropping leaves) as well as to minimise vase solution evaporation. Vases with cut stems were arranged on benches in a completely randomised design with 10 replicates. Physical treatments were applied under water in all experiments. 2.2.1. Experiment 1: stem-end bark removal With sharp scalpel blades, cut stems were subjected to five treatments: control (no bark removal), 2.5 cm bark removal, 5 cm bark removal, 7.5 cm bark removal and 10 cm bark removal from the lower end of stems. 2.2.2. Experiment 2: stem-end splitting With sharp scalpel blades, cut stems were subjected to five treatments: control (no splitting), a 2.5 cm longitudinal split from cut end of the stem, two 2.5 cm splits at right angles, a 5 cm longitudinal split from cut end of the stem and 5 cm with 2 splits at right angles. 2.2.3. Experiment 3: stem-end crushing With pliers, cut stems were subjected to five treatments: control (no crushing), 2.5 cm with one crush, 2.5 cm with two crushes, 5 cm with one crush and 5 cm with two crushes on the cut end of stems. One crush compressed the diameter of rose stems by ca. 7–10 mm and of acacia stems by ca. 4–8 mm. Second crushes were applied at right angles to the first, and compressed rose stems by ca. 10–15 mm and acacia stems by ca. 6–10 mm. 2.2.4. Experiment 4: hot water scalding Cut stem-ends were subjected to three treatments: control (no hot water scalding), 5 cm of stem base immersed in boiling (100 ◦ C) water for 30 s and 5 cm of stem base immersed in boiling water for 60 s. 2.2.5. Experiment 5: comparison of stem-end physical treatments Cut stems were subjected to five treatments selected from the above experiments: control (no stem-end treatment), 5 cm bark removal, 5 cm with 2 splits at right angles, 5 cm with 2 crushes and 5 cm of stem base immersed in hot water for 30 s. 2.2.6. Experiment 6: fresh vs. simulated-handling Cut stems were subjected to five treatments applied immediately after transportation to the laboratory (fresh-cut) and the same treatments were applied to the other half of the stems after dry storage at 4 ± 1 ◦ C for 24 h (simulated commercial handling). The treatments were control (no stem-end treatment), 5 cm bark removal, 5 cm with 2 splits at right angles, 5 cm with 2 crushes and 5 cm of stem base immersed in hot water for 30 s. 2.3. Measurements 2.3.1. Relative fresh weight (RFW) Fresh weights of cut stems were measured daily during vase life. RFW was calculated using the formula: RFW (% initial fresh weight) = (FWt /FWt=0 ) × 100; where FWt is the fresh weight of stem (g) at t = day 0, 1, 2, 3, etc., and FWt=0 is the fresh weight of the same stem (g) at t = day 0 (He et al., 2006). 2.3.2. Vase solution uptake rate (VSU) Weights of vases containing vase solution without the cut stems were recorded daily during the vase life evaluation period. Average daily VSU rate was calculated by the formula: VSU [g g−1 initial fresh weight (IFW)] = (St−1 − St )/IFW of the stem; where St is weight
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of vase solution (g) at t = day 1, 2, 3, etc., and St−1 is the weight of vase solution (g) on the previous day (Damunupola, 2009). 2.3.3. Vase life Cut stems were observed daily for visual appeal during vase life evaluation. Vase life of individual rose flower stems was considered to have ended if one or more petals had fallen, the flower showed one or more brown (necrotic) spots due to Botrytis cinerea infection or when fading became visible on most petals (van der Sman et al., 1996; Pompodakis and Joyce, 2003). Vase life of acacia foliage stems was judged to have ended when at least two fully expanded mature phyllodes on the stem had desiccated to a dry non-reflective appearance in contrast to their initial fresh, fleshy and shiny green appearance (Damunupola, 2009). 2.4. Statistical analyses Completely randomised experiment designs were used. Analysis of variance (ANOVA) on data was performed using the GLM program of the Statistical Analysis System® (SAS 9.1, SAS Institute Inc., Cary, NC, USA). Means were compared by the least significant difference (LSD) test at P ≤ 0.05. 3. Results 3.1. Bark removal RFW for rose was maintained up to day 6 of the vase life evaluation period (Fig. 1A). Thereafter, a rapid decrease was observed in stems with no bark removal (control), followed by 10 and 5 cm bark removal treatments. Bark removal of 2.5 cm maintained higher RFW until the end of the vase life evaluation period. For acacia, RFW was maintained during the first 2 d, followed by rapid declines for 10 and 7.5 cm bark removal (Fig. 1F). The other treatments of 5, 2.5 cm and no bark removal exhibited gradual slow decreases in RFW. Maximum VSU was in 2.5 cm bark removal and minimum VSU was in 10 cm bark removal (Fig. 2A). VSU was maintained up to day 7 of the vase life period, followed by an unanticipated increase in all treatments except in 10 cm bark removal. For acacia, VSU rose over the first 3 d in all treatments and then started to decrease with the greatest fall in 10 cm bark removal (Fig. 2F). Vase life for rose was significantly extended only by 2.5 cm bark removal as compared with the control (Table 1). The other bark removal treatments had no significant effects. In acacia, bark removal of 2.5 and 5 cm had no significant effects on vase life. The 7.5 and 10 cm bark removal treatments shortened vase life as compared with the control. 3.2. Stem-end splitting Following initial increases there were sharp decreases in RFW after day 5 of the vase life evaluation period in two splits of 2.5 cm and then one 2.5 cm split (Fig. 1B). Control stems with no splits maintained higher RFW than split ones towards the end of vase life period. For acacia, RFW was maintained up to day 2 followed by rapid losses in one split of 2.5 cm and then two splits of 2.5 cm (Fig. 1G). Stems with one 5 cm long split maintained highest RFW from day 4 to the end of the vase life period. VSU increased for rose up to day 5 followed by a fall with higher uptake in control stems as compared to the split stems (Fig. 2B). For acacia, VSU increased during the first 3 d of the vase evaluation period followed by rapid decrease with no difference between the various treatments (Fig. 2G). Stem-end splitting with two splits of 2.5 cm decreased vase life for rose as compared to the control (Table 1). The three other split-
Table 1 Vase life of cut rose and acacia stems with different levels of bark removal (Experiment 1), stem-end splitting (Experiment 2), stem-end crushing (Experiment 3) and hot water scalding (Experiment 4) and for comparison of different stem-end treatments (Experiment 5). Values are means ± s.e. of 10 replicate stems. Treatments
Mean vase life (d) Rose
Experiment 1 Control 2.5 cm bark removal 5 cm bark removal 7.5 cm bark removal 10 cm bark removal Experiment 2 Control 2.5 cm 1 split 2.5 cm 2 splits 5 cm 1 split 5 cm 2 splits Experiment 3 Control 2.5 cm 1 crush 2.5 cm 2 crushes 5 cm 1 crush 5 cm 2 crushes Experiment 4 Control 30 s hot water scalding 60 s hot water scalding Experiment 5 Control 5 cm bark removal 5 cm 2 splits 5 cm 2 crushes 5 cm 30 s hot water
Acacia
8.9 12.3 11.1 11.9 11.5
± ± ± ± ±
1.2b 1.2a 1.4ab 1.0ab 0.9ab
10.6 10.4 10.6 9.5 7.9
± ± ± ± ±
0.3a 0.2a 0.3a 0.3b 0.4c
8.2 7.7 5.6 7.1 7.2
± ± ± ± ±
0.9a 1.0a 0.3b 0.8ab 0.5ab
7.9 6.2 6.5 7.8 7.2
± ± ± ± ±
0.6a 0.3b 0.6ab 0.4a 0.5ab
8.2 8.5 7.9 8.7 9.7
± ± ± ± ±
0.7a 0.7a 0.4a 0.5a 0.8a
7.1 8.2 9.3 8.7 10.3
± ± ± ± ±
0.6c 0.6bc 0.4ab 0.5abc 0.7a
5.9 ± 0.5b 8.2 ± 0.8a 8.3 ± 0.7a 7.0 11.0 8.7 7.2 9.7
± ± ± ± ±
0.7b 0.9a 0.9ab 1.1b 1.1ab
5.4 ± 0.4a 5.1 ± 0.4a 4.5 ± 0.3a 5.8 6.8 6.1 6.8 7.9
± ± ± ± ±
0.3b 0.3ab 0.2b 0.3ab 0.7a
Means in a column followed by a letter in common are not significantly different at P ≤ 0.05.
ting treatments had no significant effect on vase life. For acacia, one split of 2.5 cm decreased vase life and the other three splitting treatments had no significant effects. 3.3. Stem-end crushing Similar RFW was observed for rose among all treatments during the first 6 d of the vase life period (Fig. 1C). RFW then decreased most rapidly in stems receiving two crushes of 2.5 cm length followed by the control of no stem-end crushing and then one crush of 2.5 cm. Highest RFW was observed with two crushes of 5 cm length throughout the vase life period. For acacia, two 2.5 cm long crushes and two 5 cm long crushes gave relatively higher RFW throughout the vase life evaluation period (Fig. 1H). A rapid fall in RFW consistent across treatments was observed from day 4 onwards. Control stems without crushing lost RFW more rapidly than did crushed ones in all four stem-end crushing treatments. VSU was higher in uncrushed control rose stems than in crushed ones (Fig. 2C). For A. holosericea, VSU increased up to day 5 followed by a rapid decrease, with minimum uptake by uncrushed control stems (Fig. 2H). However, no differences were observed for solution uptake in any acacia stem-end crushing treatments. No significant effects of crushing were observed on longevity for rose (Table 1). For acacia, crushed stems with two crushes had longer vase life than in the uncrushed control, but treatments with one crush had no significant effects on longevity. 3.4. Hot water scalding In roses, RFW tended to increase during the first 4 d of the vase life evaluation period followed by a decrease in non-scalded stems as compared with scalded stems (Fig. 1D). For acacia,
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Fig. 1. Changes in RFW of cut rose (Panels A–E) and acacia (Panels F–J) stems in response to various levels of bark removal (Panels A and F), stem-end splitting (Panels B and G), stem-end crushing (Panels C and H), hot water scalding (Panels D and I) and to different stem-end treatments (Panels E and J). Values are means ± s.e. of 10 replicate stems.
a consistent sharp decrease in RFW was observed more so in scalded stems as compared to in the non-scalded ones which had markedly higher RFW at the end of the vase life period (Fig. 1I).
After day 2, VSU for rose decreased up to day 4 and then increased until day 7 thereafter it fell to the end of the vase evaluation period (Fig. 2D). Un-scalded control stems had higher VSU than in scalded stems. For acacia also the non-scalded stems had higher
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Fig. 2. Changes in VSU of cut rose (Panels A–E) and acacia (Panels F–J) stems in response to various levels of bark removal (Panels A and F), stem-end splitting (Panels B and G), stem-end crushing (Panels C and H), hot water scalding (Panels D and I) and to different stem-end treatments (Panels E and J). Values are means ± s.e. of 10 replicate stems.
I. Ahmad et al. / Postharvest Biology and Technology 59 (2011) 258–264 Table 2 Vase life of cut rose and acacia stems with five different stem-end treatments (including untreated controls) applied to fresh harvested and post 4 ± 1 ◦ C dry storage for 24 h (simulated-handling) stems (Experiment 6). Values are means ± s.e. of 10 replicate stems. Treatments
Mean vase life (d) Rose
Experiment 6 Control (fresh) 5 cm bark removal (fresh) 5 cm 2 splits (fresh) 5 cm 2 crushes (fresh) 5 cm 30 s hot water (fresh) Control (simulated) 5 cm bark removal (simulated) 5 cm 2 splits (simulated) 5 cm 2 crushes (simulated) 5 cm 30 s hot water (simulated)
6.5 7.8 8.3 8.4 9.0 6.0 9.6 8.9 7.7 8.3
± ± ± ± ± ± ± ± ± ±
Acacia 0.7bc 0.5abc 0.7abc 1.0abc 0.7ab 0.5c 1.3a 1.4ab 1.0abc 0.6abc
7.8 9.9 8.0 11.6 11.0 6.6 9.5 8.7 5.3 10.3
± ± ± ± ± ± ± ± ± ±
0.4ef 0.6abcd 0.4def 1.1a 0.7ab 0.6fg 0.5bcde 0.7cde 0.4g 0.9abc
Means in a column followed by a letter in common are not significantly different at P ≤ 0.05.
VSU than in both scalded treatments (Fig. 2I). For both species there were no differences in VSU between 30 and 60 s scalding. VSU by acacia increased during the initial 2 d in all treatments followed by rapid decrease until the end of vase life period. Both scalding treatments significantly enhanced the longevity of rose, but no differences as compared to the control were recorded for acacia (Table 1). 3.5. Direct comparison of selected physical treatments Stem-end splitting of two splits of 5 cm length and bark removal of 5 cm gave higher RFW than the control with no stem-end treatment up to day 6 of vase life evaluation for rose (Fig. 1E). However, no differences were observed between the control and stem-end crushing of two crushes of 5 cm length. Hot water scalding of 30 s in boiling water (100 ◦ C) gave lower RFW than controls for days 5 and 6 only. In all treatments, RFW was rapidly lost after day 6 until the end of the vase life period. For acacia, RFW was maintained over the first 3 d followed by rapid decreases with no differences among treatments, although stem-end splitting tended to drop slightly more rapidly than in the other four (Fig. 1J). In rose, VSU was variable but tended to increase (Fig. 2E). VSU was slightly higher for control stems with no wounding followed by stem-end splitting and crushing. Bark removal and hot water scalding treatments tended to utilise the minimum solution throughout the vase life period. For acacia, VSU trended downward with no differences among the various treatments (Fig. 2J). Among the four stem end treatments only 5 cm bark removal increased rose vase life as compared to the control (Table 1). For acacia, only hot water scalding extended vase life and the other three physical stem-end treatments were without effect as compared to the control. 3.6. Fresh vs. simulated-handling All four physical treatments (Table 2) applied to fresh-cut and simulated-handling rose stems maintained higher RFW as compared to the control during the first 6 d of the vase life evaluation period (data not presented). There was no difference between fresh-cut and simulated-handling stems. However, at the end of the vase life period the control fresh-harvested stems with no physical treatment had the highest RFW followed by fresh-cut split stems. Scalded stems for both fresh-cut and simulated handling had minimum RFW at this time. For acacia, hot water scalding (Table 2) of fresh-cut and simulated-handling stems tended to maintain higher RFW compared with the other four treatments (data not presented).
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In contrast, crushing for simulated-handling stems had negative effects on RFW. A late increase in VSU was observed in rose flower stems held after simulated-handling as compared to fresh-cut stems (data not presented). This trend was particularly so in those stems with two 5 cm long splits, two 5 cm long crushes and 5 cm bark removal. For acacia, hot water scalded stems of both fresh and simulated-handling treatments had higher VSU as compared with all other treatments (data not presented). Stem-end crushing after simulated-handling gave the minimum uptake throughout the vase life evaluation period. Control rose stems from both fresh-cut and simulated-handling tended to have the shortest vase lives (Table 2). However, only simulated-handling followed by 5 cm bark removal and two 5 cm long splits gave significant vase life extensions. No significant difference was observed across fresh-cut and simulated-handling stems with the averaged means being 8.0 and 8.1 days, respectively. For acacia, stem-end crushing with two crushes of 5 cm length and hot water scalding applied to fresh-cut stems gave the longest vase lives (Table 2). In contrast, crushing of simulated-handling stems was negative in ending vase life earlier. Among simulated-handling stems, bark removal, splitting and scalding increased vase life.
4. Discussion For cut rose flowers and cut acacia foliage, physical stem-end treatments had inconsistent effects on vase life and on water relations (Figs. 1 and 2; Tables 1 and 2). For example, while bark removal from the cut stem-end was relatively effective in extending the vase life for fresh-cut rose, it tended to be ineffective and indeed negative for fresh-cut acacia (Table 1). Nonetheless, it has been shown in other work that bark stripping can increase vase water uptake and help maintain nearly constant water turnover for cut rose (de Stigter and Broekhuysen, 1986). The positive effect in the de Stigter and Broekhuysen (1986) study was attributed to exposing a larger area of stem to water thereby increasing lateral water movement into the xylem. Similar indirect water uptake was shown to occur in hollow-stemmed gerbera where water can enter via the stem cavity (van Meeteren, 1978). In Experiment 1 of the present work, bark removal from fresh-cut rose tended to increase vase life (Table 1). This tendency was reflected in better maintenance of stem RFW (Fig. 1A) and also in generally higher VSU (Fig. 2A). Similarly, extended rose vase life in Experiment 4 with stem-end scalding (Table 1) was evidently related to better RFW maintenance (Fig. 1) but conversely to lesser VSU (Fig. 2). However, where bark removal and scalding either shortened or had no effect on acacia vase life (Table 1; Experiments 1 and 4, respectively), these stem-end treatments also reduced RFW maintenance (Fig. 1F and I) and suppressed VSU (Fig. 2F and I). Thus, physical stem-end treatment effects on vase life and water relations were at least loosely correlated in fresh-cut ‘High & Mighty’ rose and Velvet Leaf acacia. Stem-end splitting was ineffective in increasing vase life with, for instance, a significant negative effect of two splits of 2.5 cm length in rose (Table 1). Also, for reasons that are not evident, stem-end splitting fairly consistently caused poorer water relations for both species (Figs. 1 and 2). Moreover, splitting of woody stems may otherwise be commercially impracticable for the likes of acacia because it is technically difficult and dangerous. Stemend crushing was similarly ineffective for rose, with no effect on vase life (Tables 1 and 2) and no clear effect on water relations (Figs. 1 and 2). However, crushing acacia stem-ends did help maintain RFW but not VSU (Figs. 1 and 2) and sometimes increased vase life (Tables 1 and 2). Hot water scalding was effective in Experiment 4 in vase life extension for rose but not acacia (Table 1). However,
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in contrast scalding gave vase life extension in fresh-cut acacia and not fresh-cut rose (Table 2). As noted above, treatment effects on vase live were therefore generally inconsistent among the same treatments applied in various experiments with fresh-cut rose and acacia (cf. Table 1 Experiments 1–4 with Table 1 Experiment 5 and Table 2 fresh-cut stems). Also, no consistent effects including significant differences were observed for physical stem-end treatments applied to fresh-cut versus simulated handling (short term storage) stems of both species (Table 2). An atypical increase in water uptake was observed towards the end of the vase life evaluation period in experiments with ‘High & Mighty’ rose (Fig. 2). This tendency was possibly an unusual varietal characteristic in that comparison (data not presented) with ‘Sweet Avalanche’ confirmed by contrast higher VSU over a longer period by ‘High & Mighty’. Anecdotally the rose growers who provided the blooms confirmed unusual postharvest characters of this particular cultivar (D. & L., Currey, pers. comm.). High water uptake may also have been facilitated by sterilization of stems with 80% ethanol, use of DICA biocide and having only one stem in 350 mL of vase solution (which remained clear throughout vase life). While there is evidence that DI water can cause artificial xylem blocking (van Ieperen et al., 2000; van Meeteren et al., 2000) it seems unlikely that there will be an interaction between the ion concentration in the water and the effect of these treatments. It is not clear whether there is likely to be an interaction between the presence or absence of biocide in the water and the effect of the treatments. If there was no biocide the treatments might be less effective because contents from damaged cells could increase bacterial growth and hence xylem blockage. In summary, the effects of physical stem-end treatments applied to fresh-cut rose and acacia and also to these species stored for a short period were inconsistent across the two species and upon repeat treatments in serial experiments. In view of this variability, and they being otherwise problematic in terms of time and effort, the physical stem-end treatments tested cannot be recommended in either scientific or commercial contexts as a practice. Acknowledgements The authors are grateful to Allan Lisle for statistical advice, to Joseph Eyre for assistance with graphics and to the Higher Education Commission, Islamabad, Pakistan, for financial support of I.A. References Abeles, F.B., Morgan, P.W., Saltveit, M.E., 1992. Ethylene in Plant Biology. Academic Press, San Diego, CA, ISBN 0-12-41451-1. Bucciarelli, B., Jung, H.G., Ostry, M.E., Anderson, N.A., Vance, C.P., 1998. Wound response characteristics as related to phenylpropanoid enzyme activity and lignin deposition in resistant and susceptible Populus tremuloides inoculated with Entoleuca mammata (Gypoxylon mammatum). Can. J. Bot. 76, 1282–1289. Ciardi, J., Klee, H., 2001. Regulation of ethylene-mediated responses at the level of the receptor. Ann. Bot. 88, 813–822. Damunupola, J.W., 2009. Xylem flow in cut Acacia holosericea stems. Ph.D. Thesis. University of Queensland, Australia. Damunupola, J.W., Qian, T., Muusers, R., Joyce, D.C., Irving, D.E., van Meeteren, U., 2010. Effect of S-carvone on vase life parameters of selected cut flower and foliage species. Postharvest Biol. Technol. 55, 66–69. Davies, F.S., Munoz, C.E., Sherman, W.B., 1981. Opening and vase life extension of peach flowers on detached shoots with sucrose and ethanol. J. Am. Soc. Hortic. Sci. 106, 809–813.
de Stigter, H.C.M., 1980. Water balance of cut and intact “Sonia” rose plants. Z. Pflanzenphysiol. 99, 137–142. de Stigter, H.C.M., Broekhuysen, A.G.M., 1986. Cut-rose performance: result of a touchy balance. Acta Hortic. 189, 137–142. Elliot, W.R., Jones, D.L., 1982. Encyclopedia of Australian Plants, 2. Lothian, Melbourne, Australia, p. 63. Evans, R., Zheng, J.M., Reid, M.S., 1996. Structural and environmental factors affecting the postharvest life of cut roses. Acta Hortic. 424, 169–173. Halevy, A.H., Byrne, T.G., Kofranek, A.M., Farnham, D.S., Thompson, J.F., Hardenburg, R.E., 1978. Evaluation of postharvest handling methods for transcontinental truck shipments of cut carnations, chrysanthemums and roses. J. Am. Soc. Hortic. Sci. 103, 151–155. Halevy, A.H., Mayak, S., 1981. Senescence and postharvest physiology of cut flowers—Part 2. Hortic. Rev. 3, 59–141. He, S.G., Joyce, D.C., Irving, D.E., Faragher, J.D., 2006. Stem-end blockage in cut Grevillea ‘Crimson Yul-lo’ inflorescences. Postharvest Biol. Technol. 41, 78–84. Horlock, F., Faragher, J., Jones, R., 2000. Acacia Cut Flower and Foliage Production Manual. Publication No. 00/57. Rural Industries Research and Development Corporation (RIRDC), Barton, ACT, Australia. Ichimura, K., Ueyama, S., 1998. Effects of temperature and application of aluminum sulfate on the postharvest life of cut rose flowers. Bull. Natl. Res. Inst. Veg., Ornamental Plants Tea, Japan 13, 51–60. Jones, R., 2001. Caring for Cut Flowers, second ed. Land Links Press, Collingwood, Victoria, Australia. Jones, R.B., Faragher, J.D., van Doorn, W.G., 1993. Water relations of cut flowering branches of Thryptomene calycina (Lindl.) Stapf. (Myrtaceae). Postharvest Biol. Technol. 3, 57–67. Joyce, D.C., Meara, S.A., Hetherington, S.E., Jones, P., 2000. Effects of cold storage on cut Grevillea ‘Sylvia’ inflorescences. Postharvest Biol. Technol. 18, 49–56. Kawaoka, A., Kawamoto, T., Ohta, H., Sekine, M., Takano, M., Shinmoyo, A., 1994. Wound-induced expression of horseradish peroxidase. Plant Cell Rep. 13, 149–154. Knee, M., 2000. Selection of biocides for use in floral preservatives. Postharvest Biol. Technol. 18, 227–234. Milner, G., 2009. Fresh-Cut Flowers. Jojo Publishing, Melbourne, Australia. Moehs, C.P., Allen, P.V., Friedman, M., Belknap, W.R., 1996. Cloning and expression of transaldolase from potato. Plant Mol. Biol. 32, 447–452. Negrel, J., Javelle, F., Paynot, M., 1993. Wound-induced tyramine hydroxy-cinnamoyl transferase in potato (Solanum tuberosum) tuber discs. J. Plant Physiol. 142, 518–524. Nijsse, J., van Meeteren, U., Keijzer, C.J., 2000. Air in xylem vessels of cut flowers. Acta Hortic. 517, 479–486. Peck-Scott, C., Kende, H., 1999. Differential regulation of genes encoding 1aminocyclopropane-1-carboxylate (ACC) synthase in etiolated pea seedlings: effects of indole-3-acetic acid, wounding, and ethylene. Plant Mol. Biol. 38, 977–982. Pompodakis, N.E., Joyce, D.C., 2003. ABA analogue effects on vase life and leaf crisping of cut ‘Baccara’ roses. Aust. J. Exp. Agric. 43, 425–428. Rapaka, V.K., Faust, J.E., Dole, J.M., Runkle, E.S., 2007. Diurnal carbohydrate dynamics affect postharvest ethylene responsiveness in portulaca (Portulaca grandiflora ‘Yubi Deep Rose’) unrooted cuttings. Postharvest Biol. Technol. 44, 293– 299. van der Sman, R.G.M., Evelo, R.G., Wilkinson, E.C., van Doorn, W.G., 1996. Quality loss in packed rose flowers due to Botrytis cinerea infection as related to temperature regimes and packaging design. Postharvest Biol. Technol. 7, 341–350. van Doorn, W.G., 1997. Water relations of cut flowers. Hortic. Rev. 18, 1–85. van Doorn, W.G., Perik, R.R.J., 1990. Hydroxyquinoline citrate and low pH prevent vascular blockage in stems of cut rose flowers by reducing the number of bacteria. J. Am. Soc. Hortic. Sci. 115, 979–981. van Doorn, W.G., Cruz, P., 2000. Evidence for a wounding-induced xylem occlusion in stems of cut chrysanthemum flowers. Postharvest Biol. Technol. 19, 73–83. van Doorn, W.G., Perik, R.R.J., Belde, P.J.M., 1993. Effects of surfactants on the longevity of dry stored cut stems of rose, Bouvardia and Astilbe. Postharvest Biol. Technol. 3, 69–76. van Ieperen, W., van Meeteren, U., van Gelder, H., 2000. Fluid ionic composition influences hydraulic conductance of xylem conduits. J. Exp. Bot. 51, 769–776. van Meeteren, U., 1978. Water relations and keeping quality of cut gerbera flowers. I. The cause of stem break. Sci. Hortic. 8, 65–74. van Meeteren, U., van Gelder, H., van Ieperen, W., 2000. Reconsideration of the use of deionised water as vase water in postharvest experiments on cut flowers. Postharvest Biol. Technol. 18, 169–181. Weiner, G., Liese, W., 1995. Wound response in the stem of Royal palm. IAWA J. 16, 433–442. Williamson, V.G., Faragher, J., Parsons, S., Franz, P., 2002. Inhibiting the Postharvest Wounding Responses in Wildflowers. Publication No. 02/114. Rural Industries Research and Development Corporation (RIRDC), Barton, ACT, Australia.
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Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio
Physical stem-end treatment effects on cut rose and acacia vase life and water relations Iftikhar Ahmad a,b,∗ , Daryl C. Joyce b , John D. Faragher b a b
Institute of Horticultural Sciences, University of Agriculture, Faisalabad 38040, Pakistan The University of Queensland, Centre for Native Floriculture, School of Land, Crop and Food Sciences, Gatton, QLD 4343, Australia
a r t i c l e
i n f o
Article history: Received 11 May 2010 Accepted 1 November 2010 Keywords: Bark removal Hot water scalding Relative fresh weight Rose Stem-end splitting Stem-end crushing Vase solution uptake Vase life Water relations Wattle
a b s t r a c t Cut Rosa hybrida cv. High & Mighty flowers and Acacia holosericea (Velvet Leaf Wattle) foliage were subjected to various physical stem-end treatments as practised by florists. Their effects on longevity (vase life) and water relations [relative fresh weight (RFW) and vase solution uptake (VSU)] were quantified. All vase water contained sodium dichloroisocyanurate (DICA) biocide. Bark removal had either positive or neutral effects on the vase life of fresh-cut rose and had either neutral or negative effects on fresh-cut acacia. Stem-end splitting had either no or negative effects on the vase life of fresh-cut rose and acacia. However, both bark removal and stem-end splitting increased the vase life of both species when applied after short term storage for 24 h at 4 ◦ C. Crushing stems had no effect on the vase life of fresh-cut rose, but tends to increase the vase life of fresh-cut acacia. Hot water scalding either increased or had no effect on the vase lives of rose and acacia. The tendency for bark removal to increase vase life of fresh-cut rose was associated with better maintenance of RFW and sustained VSU. However, for the most part, stem-end treatments had typically negative or neutral effects on RFW of fresh-cut rose and acacia. Likewise, the treatments had mostly negative or neutral effects on VSU. Overall for both species, there is little or no benefit and potentially negative effects on vase life, RFW and VSU of applying stem-end treatments as sometimes advocated by florists. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Cut flowers and foliage can have limited commercial value because they dehydrate during vase life as a result of decreased water uptake. This is true for cut rose flowers (van Doorn, 1997) and cut acacia foliage (Horlock et al., 2000; Williamson et al., 2002; Damunupola, 2009). In cut roses, water stress caused by xylem vessel blockage is a major cause of vase life termination due to premature petal wilting, lack of proper flower opening, wilting of foliage and/or bending of the pedicel (‘bent neck’) (van Doorn and Perik, 1990; Knee, 2000). In the case of Acacia holosericea (Velvet Leaf Wattle) foliage, a very short vase life of 4–7 d limits its commercial potential. Insufficient water uptake due to possible stem-end occlusion leads to early phyllode (leaf) wilting and desiccation in this otherwise promising Australian native cut foliage crop (Damunupola et al., 2010). Cut flowers and foliage develop water deficit even when placed in water (Halevy and Mayak, 1981; van Doorn, 1997). A negative
∗ Corresponding author at: Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Punjab 38040, Pakistan. Tel.: +92 333 841 7286; fax: +92 41 920 1085. E-mail address: [email protected] (I. Ahmad). 0925-5214/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2010.11.001
water balance develops when transpiration is greater than uptake (Halevy et al., 1978). Impaired water uptake is typically caused by cut stem occlusions due to microbial, physiological and physical plugging of xylem vessels (e.g. Nijsse et al., 2000; van Doorn and Cruz, 2000). Resistance to water flow in cut rose stems rises markedly soon after they are harvested (Evans et al., 1996). Numerous studies have demonstrated positive effects of various chemical additives (e.g. biocides, surfactants, ethylene inhibitors, wound healing enzyme inhibitors) on the postharvest water relations and longevity of cut flowers (e.g. de Stigter, 1980; Jones et al., 1993; van Doorn et al., 1993). However, despite anecdotal evidence of positive effects (Milner, 2009), improving postharvest water relations of cut flowers and foliage by various physical stem-end treatments is little researched. There has been research into bark removal at the base of cut rose stems to increase water uptake (de Stigter and Broekhuysen, 1986). This physical treatment effected increased water uptake and a 25% increase in FW compared with the control. Florists sometimes advocate splitting or crushing stems and also removing bark at the base of the stem to increase water uptake and extend vase life (Jones, 2001; Milner, 2009). These practices are thought to increase exposure of the vasculature to vase solution. Dipping of stem-ends into scalding (almost boiling) water is also recommended in some cases. This is particularly so for stems which contain latex with
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a view to preventing it from exuding and blocking xylem vessels (Jones, 2001). However, scalding might also sterilize stem-ends and/or destroy enzymes that otherwise lead to blockages in water uptake. Dipping of the base of Thryptomene calycina stems into 100 ◦ C water for 1 min markedly increased vase life (Jones et al., 1993). On the other hand, physical treatments are likely to damage xylem vessels, allow ingress of microbes and increase nutrient supply for microbes, which occlude stems (Jones, 2001). Other possible side effects of wounding tissues include stimulated defence-related enzyme activity and gene expression; e.g. peroxidase (Kawaoka et al., 1994) and ACC oxidase (Peck-Scott and Kende, 1999). These responses lead to biosynthesis of suberin, lignin and other wound healing compounds (Negrel et al., 1993; Moehs et al., 1996), including deposition of mucilage and tylose formation (Weiner and Liese, 1995) along with deposition of gums in the lumen of xylem conduits (Davies et al., 1981). Production of such compounds in nature serves, by xylem occlusion, to reduce entrance of microbes into damaged tissues (Bucciarelli et al., 1998). Wounding may also stimulate ethylene production (Ciardi and Klee, 2001) and promote senescence (Abeles et al., 1992) and abscission (Rapaka et al., 2007). In addition to improving water uptake, other approaches to maintaining a positive postharvest water balance for cut flowers and foliage include minimising water loss though reduction in leaf area, keeping them in an environment conducive to less water loss (viz. low temperature and high RH) and providing compatible osmotica (e.g. sucrose) in vase and/or pulsing solutions (Halevy and Mayak, 1981; Jones et al., 1993; van Doorn, 1997). The current experiments compared various physical stem-end treatments as used by florists (i.e. bark removal, stem-end splitting, stem-end crushing and hot water scalding) with the aim to improve the postharvest water relations of cut rose and acacia. It was hypothesised that the various physical stem-end treatments would improve water uptake by presenting a larger surface area of stem xylem conduits to increase direct and indirect access of water. 2. Materials and methods 2.1. Plant materials Cut stems of rose (Rosa hybrida L. ‘High & Mighty’) harvested when petals were about to reflex (Ichimura and Ueyama, 1998) and Velvet Leaf Wattle (A. holosericea A. Cunn. ex G. Don; Elliot and Jones, 1982) foliage were obtained from greenhouse and field plantings, respectively, at Karalee (152◦ 50 E, 27◦ 32 S), Queensland, Australia. They were transported to the University of Queensland, Gatton postharvest laboratory within 2 h of harvest. Harvests were conducted between 0600 and 0800 h serially from April to July (late autumn to early spring). Stems were harvested with clean sharp secateurs and placed into buckets of deionised water (DI), covered with polyethylene film and transported. Stems of rose and acacia were ca. 50 cm in length. Stem-ends were dipped into 80% (v/v) ethanol solution for 2–3 s for surface disinfection, rinsed with DI and re-trimmed under DI to remove stem-end air emboli. Resultant stem lengths were ca. 40 cm bearing the three upper leaves for roses and four phyllodes for acacia. 2.2. Experiment design and treatments Six experiments were conducted in a vase life evaluation room maintained at ca. 20 ± 2 ◦ C and 80 ± 20% relative humidity under a PAR flux of 8–12 mol m−2 s−1 from white fluorescent tubes at flower level on a daily 12 h photoperiod and under 0.2–0.4 m s−1 air speed. In each experiment, stems were placed individually into 350 mL plastic vases containing DI with 10 mg L−1 available chlo-
259
rine as sodium dichloroisocyanurate (DICA; Joyce et al., 2000). Low-density polyethylene film was used to cover the mouth of each vase to limit entrance of dust and foreign objects (e.g. dropping leaves) as well as to minimise vase solution evaporation. Vases with cut stems were arranged on benches in a completely randomised design with 10 replicates. Physical treatments were applied under water in all experiments. 2.2.1. Experiment 1: stem-end bark removal With sharp scalpel blades, cut stems were subjected to five treatments: control (no bark removal), 2.5 cm bark removal, 5 cm bark removal, 7.5 cm bark removal and 10 cm bark removal from the lower end of stems. 2.2.2. Experiment 2: stem-end splitting With sharp scalpel blades, cut stems were subjected to five treatments: control (no splitting), a 2.5 cm longitudinal split from cut end of the stem, two 2.5 cm splits at right angles, a 5 cm longitudinal split from cut end of the stem and 5 cm with 2 splits at right angles. 2.2.3. Experiment 3: stem-end crushing With pliers, cut stems were subjected to five treatments: control (no crushing), 2.5 cm with one crush, 2.5 cm with two crushes, 5 cm with one crush and 5 cm with two crushes on the cut end of stems. One crush compressed the diameter of rose stems by ca. 7–10 mm and of acacia stems by ca. 4–8 mm. Second crushes were applied at right angles to the first, and compressed rose stems by ca. 10–15 mm and acacia stems by ca. 6–10 mm. 2.2.4. Experiment 4: hot water scalding Cut stem-ends were subjected to three treatments: control (no hot water scalding), 5 cm of stem base immersed in boiling (100 ◦ C) water for 30 s and 5 cm of stem base immersed in boiling water for 60 s. 2.2.5. Experiment 5: comparison of stem-end physical treatments Cut stems were subjected to five treatments selected from the above experiments: control (no stem-end treatment), 5 cm bark removal, 5 cm with 2 splits at right angles, 5 cm with 2 crushes and 5 cm of stem base immersed in hot water for 30 s. 2.2.6. Experiment 6: fresh vs. simulated-handling Cut stems were subjected to five treatments applied immediately after transportation to the laboratory (fresh-cut) and the same treatments were applied to the other half of the stems after dry storage at 4 ± 1 ◦ C for 24 h (simulated commercial handling). The treatments were control (no stem-end treatment), 5 cm bark removal, 5 cm with 2 splits at right angles, 5 cm with 2 crushes and 5 cm of stem base immersed in hot water for 30 s. 2.3. Measurements 2.3.1. Relative fresh weight (RFW) Fresh weights of cut stems were measured daily during vase life. RFW was calculated using the formula: RFW (% initial fresh weight) = (FWt /FWt=0 ) × 100; where FWt is the fresh weight of stem (g) at t = day 0, 1, 2, 3, etc., and FWt=0 is the fresh weight of the same stem (g) at t = day 0 (He et al., 2006). 2.3.2. Vase solution uptake rate (VSU) Weights of vases containing vase solution without the cut stems were recorded daily during the vase life evaluation period. Average daily VSU rate was calculated by the formula: VSU [g g−1 initial fresh weight (IFW)] = (St−1 − St )/IFW of the stem; where St is weight
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of vase solution (g) at t = day 1, 2, 3, etc., and St−1 is the weight of vase solution (g) on the previous day (Damunupola, 2009). 2.3.3. Vase life Cut stems were observed daily for visual appeal during vase life evaluation. Vase life of individual rose flower stems was considered to have ended if one or more petals had fallen, the flower showed one or more brown (necrotic) spots due to Botrytis cinerea infection or when fading became visible on most petals (van der Sman et al., 1996; Pompodakis and Joyce, 2003). Vase life of acacia foliage stems was judged to have ended when at least two fully expanded mature phyllodes on the stem had desiccated to a dry non-reflective appearance in contrast to their initial fresh, fleshy and shiny green appearance (Damunupola, 2009). 2.4. Statistical analyses Completely randomised experiment designs were used. Analysis of variance (ANOVA) on data was performed using the GLM program of the Statistical Analysis System® (SAS 9.1, SAS Institute Inc., Cary, NC, USA). Means were compared by the least significant difference (LSD) test at P ≤ 0.05. 3. Results 3.1. Bark removal RFW for rose was maintained up to day 6 of the vase life evaluation period (Fig. 1A). Thereafter, a rapid decrease was observed in stems with no bark removal (control), followed by 10 and 5 cm bark removal treatments. Bark removal of 2.5 cm maintained higher RFW until the end of the vase life evaluation period. For acacia, RFW was maintained during the first 2 d, followed by rapid declines for 10 and 7.5 cm bark removal (Fig. 1F). The other treatments of 5, 2.5 cm and no bark removal exhibited gradual slow decreases in RFW. Maximum VSU was in 2.5 cm bark removal and minimum VSU was in 10 cm bark removal (Fig. 2A). VSU was maintained up to day 7 of the vase life period, followed by an unanticipated increase in all treatments except in 10 cm bark removal. For acacia, VSU rose over the first 3 d in all treatments and then started to decrease with the greatest fall in 10 cm bark removal (Fig. 2F). Vase life for rose was significantly extended only by 2.5 cm bark removal as compared with the control (Table 1). The other bark removal treatments had no significant effects. In acacia, bark removal of 2.5 and 5 cm had no significant effects on vase life. The 7.5 and 10 cm bark removal treatments shortened vase life as compared with the control. 3.2. Stem-end splitting Following initial increases there were sharp decreases in RFW after day 5 of the vase life evaluation period in two splits of 2.5 cm and then one 2.5 cm split (Fig. 1B). Control stems with no splits maintained higher RFW than split ones towards the end of vase life period. For acacia, RFW was maintained up to day 2 followed by rapid losses in one split of 2.5 cm and then two splits of 2.5 cm (Fig. 1G). Stems with one 5 cm long split maintained highest RFW from day 4 to the end of the vase life period. VSU increased for rose up to day 5 followed by a fall with higher uptake in control stems as compared to the split stems (Fig. 2B). For acacia, VSU increased during the first 3 d of the vase evaluation period followed by rapid decrease with no difference between the various treatments (Fig. 2G). Stem-end splitting with two splits of 2.5 cm decreased vase life for rose as compared to the control (Table 1). The three other split-
Table 1 Vase life of cut rose and acacia stems with different levels of bark removal (Experiment 1), stem-end splitting (Experiment 2), stem-end crushing (Experiment 3) and hot water scalding (Experiment 4) and for comparison of different stem-end treatments (Experiment 5). Values are means ± s.e. of 10 replicate stems. Treatments
Mean vase life (d) Rose
Experiment 1 Control 2.5 cm bark removal 5 cm bark removal 7.5 cm bark removal 10 cm bark removal Experiment 2 Control 2.5 cm 1 split 2.5 cm 2 splits 5 cm 1 split 5 cm 2 splits Experiment 3 Control 2.5 cm 1 crush 2.5 cm 2 crushes 5 cm 1 crush 5 cm 2 crushes Experiment 4 Control 30 s hot water scalding 60 s hot water scalding Experiment 5 Control 5 cm bark removal 5 cm 2 splits 5 cm 2 crushes 5 cm 30 s hot water
Acacia
8.9 12.3 11.1 11.9 11.5
± ± ± ± ±
1.2b 1.2a 1.4ab 1.0ab 0.9ab
10.6 10.4 10.6 9.5 7.9
± ± ± ± ±
0.3a 0.2a 0.3a 0.3b 0.4c
8.2 7.7 5.6 7.1 7.2
± ± ± ± ±
0.9a 1.0a 0.3b 0.8ab 0.5ab
7.9 6.2 6.5 7.8 7.2
± ± ± ± ±
0.6a 0.3b 0.6ab 0.4a 0.5ab
8.2 8.5 7.9 8.7 9.7
± ± ± ± ±
0.7a 0.7a 0.4a 0.5a 0.8a
7.1 8.2 9.3 8.7 10.3
± ± ± ± ±
0.6c 0.6bc 0.4ab 0.5abc 0.7a
5.9 ± 0.5b 8.2 ± 0.8a 8.3 ± 0.7a 7.0 11.0 8.7 7.2 9.7
± ± ± ± ±
0.7b 0.9a 0.9ab 1.1b 1.1ab
5.4 ± 0.4a 5.1 ± 0.4a 4.5 ± 0.3a 5.8 6.8 6.1 6.8 7.9
± ± ± ± ±
0.3b 0.3ab 0.2b 0.3ab 0.7a
Means in a column followed by a letter in common are not significantly different at P ≤ 0.05.
ting treatments had no significant effect on vase life. For acacia, one split of 2.5 cm decreased vase life and the other three splitting treatments had no significant effects. 3.3. Stem-end crushing Similar RFW was observed for rose among all treatments during the first 6 d of the vase life period (Fig. 1C). RFW then decreased most rapidly in stems receiving two crushes of 2.5 cm length followed by the control of no stem-end crushing and then one crush of 2.5 cm. Highest RFW was observed with two crushes of 5 cm length throughout the vase life period. For acacia, two 2.5 cm long crushes and two 5 cm long crushes gave relatively higher RFW throughout the vase life evaluation period (Fig. 1H). A rapid fall in RFW consistent across treatments was observed from day 4 onwards. Control stems without crushing lost RFW more rapidly than did crushed ones in all four stem-end crushing treatments. VSU was higher in uncrushed control rose stems than in crushed ones (Fig. 2C). For A. holosericea, VSU increased up to day 5 followed by a rapid decrease, with minimum uptake by uncrushed control stems (Fig. 2H). However, no differences were observed for solution uptake in any acacia stem-end crushing treatments. No significant effects of crushing were observed on longevity for rose (Table 1). For acacia, crushed stems with two crushes had longer vase life than in the uncrushed control, but treatments with one crush had no significant effects on longevity. 3.4. Hot water scalding In roses, RFW tended to increase during the first 4 d of the vase life evaluation period followed by a decrease in non-scalded stems as compared with scalded stems (Fig. 1D). For acacia,
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Fig. 1. Changes in RFW of cut rose (Panels A–E) and acacia (Panels F–J) stems in response to various levels of bark removal (Panels A and F), stem-end splitting (Panels B and G), stem-end crushing (Panels C and H), hot water scalding (Panels D and I) and to different stem-end treatments (Panels E and J). Values are means ± s.e. of 10 replicate stems.
a consistent sharp decrease in RFW was observed more so in scalded stems as compared to in the non-scalded ones which had markedly higher RFW at the end of the vase life period (Fig. 1I).
After day 2, VSU for rose decreased up to day 4 and then increased until day 7 thereafter it fell to the end of the vase evaluation period (Fig. 2D). Un-scalded control stems had higher VSU than in scalded stems. For acacia also the non-scalded stems had higher
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Fig. 2. Changes in VSU of cut rose (Panels A–E) and acacia (Panels F–J) stems in response to various levels of bark removal (Panels A and F), stem-end splitting (Panels B and G), stem-end crushing (Panels C and H), hot water scalding (Panels D and I) and to different stem-end treatments (Panels E and J). Values are means ± s.e. of 10 replicate stems.
I. Ahmad et al. / Postharvest Biology and Technology 59 (2011) 258–264 Table 2 Vase life of cut rose and acacia stems with five different stem-end treatments (including untreated controls) applied to fresh harvested and post 4 ± 1 ◦ C dry storage for 24 h (simulated-handling) stems (Experiment 6). Values are means ± s.e. of 10 replicate stems. Treatments
Mean vase life (d) Rose
Experiment 6 Control (fresh) 5 cm bark removal (fresh) 5 cm 2 splits (fresh) 5 cm 2 crushes (fresh) 5 cm 30 s hot water (fresh) Control (simulated) 5 cm bark removal (simulated) 5 cm 2 splits (simulated) 5 cm 2 crushes (simulated) 5 cm 30 s hot water (simulated)
6.5 7.8 8.3 8.4 9.0 6.0 9.6 8.9 7.7 8.3
± ± ± ± ± ± ± ± ± ±
Acacia 0.7bc 0.5abc 0.7abc 1.0abc 0.7ab 0.5c 1.3a 1.4ab 1.0abc 0.6abc
7.8 9.9 8.0 11.6 11.0 6.6 9.5 8.7 5.3 10.3
± ± ± ± ± ± ± ± ± ±
0.4ef 0.6abcd 0.4def 1.1a 0.7ab 0.6fg 0.5bcde 0.7cde 0.4g 0.9abc
Means in a column followed by a letter in common are not significantly different at P ≤ 0.05.
VSU than in both scalded treatments (Fig. 2I). For both species there were no differences in VSU between 30 and 60 s scalding. VSU by acacia increased during the initial 2 d in all treatments followed by rapid decrease until the end of vase life period. Both scalding treatments significantly enhanced the longevity of rose, but no differences as compared to the control were recorded for acacia (Table 1). 3.5. Direct comparison of selected physical treatments Stem-end splitting of two splits of 5 cm length and bark removal of 5 cm gave higher RFW than the control with no stem-end treatment up to day 6 of vase life evaluation for rose (Fig. 1E). However, no differences were observed between the control and stem-end crushing of two crushes of 5 cm length. Hot water scalding of 30 s in boiling water (100 ◦ C) gave lower RFW than controls for days 5 and 6 only. In all treatments, RFW was rapidly lost after day 6 until the end of the vase life period. For acacia, RFW was maintained over the first 3 d followed by rapid decreases with no differences among treatments, although stem-end splitting tended to drop slightly more rapidly than in the other four (Fig. 1J). In rose, VSU was variable but tended to increase (Fig. 2E). VSU was slightly higher for control stems with no wounding followed by stem-end splitting and crushing. Bark removal and hot water scalding treatments tended to utilise the minimum solution throughout the vase life period. For acacia, VSU trended downward with no differences among the various treatments (Fig. 2J). Among the four stem end treatments only 5 cm bark removal increased rose vase life as compared to the control (Table 1). For acacia, only hot water scalding extended vase life and the other three physical stem-end treatments were without effect as compared to the control. 3.6. Fresh vs. simulated-handling All four physical treatments (Table 2) applied to fresh-cut and simulated-handling rose stems maintained higher RFW as compared to the control during the first 6 d of the vase life evaluation period (data not presented). There was no difference between fresh-cut and simulated-handling stems. However, at the end of the vase life period the control fresh-harvested stems with no physical treatment had the highest RFW followed by fresh-cut split stems. Scalded stems for both fresh-cut and simulated handling had minimum RFW at this time. For acacia, hot water scalding (Table 2) of fresh-cut and simulated-handling stems tended to maintain higher RFW compared with the other four treatments (data not presented).
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In contrast, crushing for simulated-handling stems had negative effects on RFW. A late increase in VSU was observed in rose flower stems held after simulated-handling as compared to fresh-cut stems (data not presented). This trend was particularly so in those stems with two 5 cm long splits, two 5 cm long crushes and 5 cm bark removal. For acacia, hot water scalded stems of both fresh and simulated-handling treatments had higher VSU as compared with all other treatments (data not presented). Stem-end crushing after simulated-handling gave the minimum uptake throughout the vase life evaluation period. Control rose stems from both fresh-cut and simulated-handling tended to have the shortest vase lives (Table 2). However, only simulated-handling followed by 5 cm bark removal and two 5 cm long splits gave significant vase life extensions. No significant difference was observed across fresh-cut and simulated-handling stems with the averaged means being 8.0 and 8.1 days, respectively. For acacia, stem-end crushing with two crushes of 5 cm length and hot water scalding applied to fresh-cut stems gave the longest vase lives (Table 2). In contrast, crushing of simulated-handling stems was negative in ending vase life earlier. Among simulated-handling stems, bark removal, splitting and scalding increased vase life.
4. Discussion For cut rose flowers and cut acacia foliage, physical stem-end treatments had inconsistent effects on vase life and on water relations (Figs. 1 and 2; Tables 1 and 2). For example, while bark removal from the cut stem-end was relatively effective in extending the vase life for fresh-cut rose, it tended to be ineffective and indeed negative for fresh-cut acacia (Table 1). Nonetheless, it has been shown in other work that bark stripping can increase vase water uptake and help maintain nearly constant water turnover for cut rose (de Stigter and Broekhuysen, 1986). The positive effect in the de Stigter and Broekhuysen (1986) study was attributed to exposing a larger area of stem to water thereby increasing lateral water movement into the xylem. Similar indirect water uptake was shown to occur in hollow-stemmed gerbera where water can enter via the stem cavity (van Meeteren, 1978). In Experiment 1 of the present work, bark removal from fresh-cut rose tended to increase vase life (Table 1). This tendency was reflected in better maintenance of stem RFW (Fig. 1A) and also in generally higher VSU (Fig. 2A). Similarly, extended rose vase life in Experiment 4 with stem-end scalding (Table 1) was evidently related to better RFW maintenance (Fig. 1) but conversely to lesser VSU (Fig. 2). However, where bark removal and scalding either shortened or had no effect on acacia vase life (Table 1; Experiments 1 and 4, respectively), these stem-end treatments also reduced RFW maintenance (Fig. 1F and I) and suppressed VSU (Fig. 2F and I). Thus, physical stem-end treatment effects on vase life and water relations were at least loosely correlated in fresh-cut ‘High & Mighty’ rose and Velvet Leaf acacia. Stem-end splitting was ineffective in increasing vase life with, for instance, a significant negative effect of two splits of 2.5 cm length in rose (Table 1). Also, for reasons that are not evident, stem-end splitting fairly consistently caused poorer water relations for both species (Figs. 1 and 2). Moreover, splitting of woody stems may otherwise be commercially impracticable for the likes of acacia because it is technically difficult and dangerous. Stemend crushing was similarly ineffective for rose, with no effect on vase life (Tables 1 and 2) and no clear effect on water relations (Figs. 1 and 2). However, crushing acacia stem-ends did help maintain RFW but not VSU (Figs. 1 and 2) and sometimes increased vase life (Tables 1 and 2). Hot water scalding was effective in Experiment 4 in vase life extension for rose but not acacia (Table 1). However,
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in contrast scalding gave vase life extension in fresh-cut acacia and not fresh-cut rose (Table 2). As noted above, treatment effects on vase live were therefore generally inconsistent among the same treatments applied in various experiments with fresh-cut rose and acacia (cf. Table 1 Experiments 1–4 with Table 1 Experiment 5 and Table 2 fresh-cut stems). Also, no consistent effects including significant differences were observed for physical stem-end treatments applied to fresh-cut versus simulated handling (short term storage) stems of both species (Table 2). An atypical increase in water uptake was observed towards the end of the vase life evaluation period in experiments with ‘High & Mighty’ rose (Fig. 2). This tendency was possibly an unusual varietal characteristic in that comparison (data not presented) with ‘Sweet Avalanche’ confirmed by contrast higher VSU over a longer period by ‘High & Mighty’. Anecdotally the rose growers who provided the blooms confirmed unusual postharvest characters of this particular cultivar (D. & L., Currey, pers. comm.). High water uptake may also have been facilitated by sterilization of stems with 80% ethanol, use of DICA biocide and having only one stem in 350 mL of vase solution (which remained clear throughout vase life). While there is evidence that DI water can cause artificial xylem blocking (van Ieperen et al., 2000; van Meeteren et al., 2000) it seems unlikely that there will be an interaction between the ion concentration in the water and the effect of these treatments. It is not clear whether there is likely to be an interaction between the presence or absence of biocide in the water and the effect of the treatments. If there was no biocide the treatments might be less effective because contents from damaged cells could increase bacterial growth and hence xylem blockage. In summary, the effects of physical stem-end treatments applied to fresh-cut rose and acacia and also to these species stored for a short period were inconsistent across the two species and upon repeat treatments in serial experiments. In view of this variability, and they being otherwise problematic in terms of time and effort, the physical stem-end treatments tested cannot be recommended in either scientific or commercial contexts as a practice. Acknowledgements The authors are grateful to Allan Lisle for statistical advice, to Joseph Eyre for assistance with graphics and to the Higher Education Commission, Islamabad, Pakistan, for financial support of I.A. References Abeles, F.B., Morgan, P.W., Saltveit, M.E., 1992. Ethylene in Plant Biology. Academic Press, San Diego, CA, ISBN 0-12-41451-1. Bucciarelli, B., Jung, H.G., Ostry, M.E., Anderson, N.A., Vance, C.P., 1998. Wound response characteristics as related to phenylpropanoid enzyme activity and lignin deposition in resistant and susceptible Populus tremuloides inoculated with Entoleuca mammata (Gypoxylon mammatum). Can. J. Bot. 76, 1282–1289. Ciardi, J., Klee, H., 2001. Regulation of ethylene-mediated responses at the level of the receptor. Ann. Bot. 88, 813–822. Damunupola, J.W., 2009. Xylem flow in cut Acacia holosericea stems. Ph.D. Thesis. University of Queensland, Australia. Damunupola, J.W., Qian, T., Muusers, R., Joyce, D.C., Irving, D.E., van Meeteren, U., 2010. Effect of S-carvone on vase life parameters of selected cut flower and foliage species. Postharvest Biol. Technol. 55, 66–69. Davies, F.S., Munoz, C.E., Sherman, W.B., 1981. Opening and vase life extension of peach flowers on detached shoots with sucrose and ethanol. J. Am. Soc. Hortic. Sci. 106, 809–813.
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