Postharvest life of Bird-of-Paradise inflorescences

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Postharvest Biology and Technology 48 (2008) 259–263

Postharvest life of Bird-of-Paradise inflorescences Emma Ruth V. Bayogan a , Teeranuch Jaroenkit b , Robert E. Paull c,∗ a

Department of Biological Sciences and Environmental Studies, University of the Philippines in Mindanao, Mintal, Tugbok District, Davao City 8000, Philippines b Department of Horticulture, Faculty of Agricultural Production, Maejo University, Chiang Mai 50290, Thailand c Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, 3190 Maile Way, Honolulu, HI 96822, USA Received 6 June 2007; accepted 13 October 2007

Abstract The postharvest life of Bird-of-Paradise (Strelitzia reginae Ait., Strelitziaceae) inflorescence is reported to range from 6 to 16 d. The objective of the experiments reported here was to determine what factors influenced postharvest life. Inflorescences were harvested at different stages of development and subjected to different prepacking and post packing treatments to extend postharvest life. Treatments included a simulated shipping period of 2 d at 22 ◦ C. More mature inflorescences with a pronounced orange knuckle on the upper side of the unopen bract or just emerged first floret at harvest had longer vase lives, developed a higher number of florets and the florets had more color development. Stem length had a significant effect on postharvest life of mature inflorescences; the longer the stem, the greater the postharvest life. Overnight treatment of Bird-of-Paradise inflorescences prior to packing with 20 or 40% sucrose, 250 or 500 mg L−1 8-hydroxyquinoline citrate (8-HQC) plus 150 or 300 mg L−1 citric acid or silver thiosulfate for 10 min and gibberellic acid overnight increased postharvest life from 10 to about 13 d. Inflorescences held in 10% sucrose and 200 mg L−1 8-HQC with 10 mg L−1 silver nitrate after unpacking had 1.2 times longer postharvest life than the deionized water control. Packing in a carton and holding for 2 d at 22 ◦ C did not increase postharvest life, except when the inflorescence was treated with 5% sucrose before packing. Similarly, a wet sponge on the stem during the pack period, sodium hypochlorite (50 and 100 mg L−1 ), 200 mg L−1 8-HQC, or 25 mmol L−1 aminooxyacetic acid in the holding solutions did not increase postharvest life. The results obtained suggested that Bird-of-Paradise inflorescences should be harvested when the first floret was just about to emerge from the boat, pulsed with 5% sucrose overnight then shipped and upon unpacking held in 10% sucrose, 200 mg L−1 8-HQC and 10 mg L−1 silver nitrate. © 2007 Elsevier B.V. All rights reserved. Keywords: Vase life; Inflorescences; Pulsing; Pretreatment; Holding solutions; Maturity; Stem length

Tropical flowers often have colorful bracts and flowers that give the flowers its appeal. The Bird-of-Paradise (Strelitzia reginae Ait.) has a large bract or boat with three upright orange sepals and three modified fused petals. The postharvest life has been reported to vary considerably from 6 to 8 d (Halevy et al., 1978) to 38.5 d (El-Saka et al., 1995), more commonly the postharvest life varies from 6 to 16 d. This difference may reflect in part growing conditions, maturity at harvest, different holding conditions, the absence of a simulated shipping period and different criteria used for evaluation of inflorescence postharvest life. The difference in evaluation criteria has been suggested to explain the large differences reported for heliconia postharvest life (Criley and Paull, 1993). Bird-of-Paradise senes-

∗

Corresponding author. E-mail address: [email protected] (R.E. Paull).

0925-5214/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2007.10.010

cence symptoms include floret desiccation and bract darkening (Jaroenkit and Paull, 2003) and commercial flower preservatives have not been shown to consistently extend postharvest life. Postharvest life is terminated when the last floret has withered (Halevy et al., 1978) and when the bract base darkens and the leaves curl (Jaroenkit and Paull, 2003). The cause for the loss of postharvest life is probably a rapid decline in water uptake after harvest, associated with a possible blockage of the stem vascular tissue and bract senescence (Jaroenkit and Paull, 2003). Bird-of-Paradise’s postharvest life is increased by chemical treatments for short periods prior to packing and vase holding solutions (Halevy and Mayak, 1979). The recommended solution for treating Bird-of-Paradise before packing is 10% sucrose + 250 mg L−1 8-hydroxyquinoline citrate (8HQC) + 150 mg L−1 citric acid for 48 h at 22 ◦ C (Halevy et al., 1978). Solutions used for pretreating Bird-of-Paradise inflores-

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cence also show a significant effect on floret opening when used as holding solutions, and the starting time of pretreatment, before or after storage, does not affect the solution’s ability to extend postharvest life (Halevy et al., 1978). A short dip of the whole inflorescence in benzyladenine before packing does not increase postharvest life (Paull and Chantrachit, 2001). El-Saka et al. (1995) reported that the best postharvest treatment for Bird-of-Paradise was a dip in silver thiosulfate (STS) for 10 min and holding in 25 mg L−1 gibberellic acid overnight and then in a vase solution containing 10% sucrose + 200 mg L−1 8-HQS + 150 mg L−1 citric acid. This regime was reported to extend postharvest life from 15.5 to 38.5 d. However, it is not clear why the postharvest life of the control Bird-of-Paradise inflorescence (El-Saka et al., 1995) was nearly twice that of other reports (Criley and Paull, 1993; Halevy et al., 1978; Sacalis, 1993). In addition, no simulated packing was used in this series of experiments. The research reported here was undertaken to determine the effect of inflorescence maturity, stem length and postharvest chemical treatments on postharvest life with the inclusion of 2 d simulated shipping period in a carton. The results were aimed at providing to local growers and shippers optimum harvest and handling procedures to assist in shipping to consumers a consistent supply of a long lived high quality product.

1.2. Evaluation The end of postharvest life was defined as when 50% of the individual florets (approximately 1–3 florets/inflorescence) showed discoloration, wilting, drying, or darkening of the bracts. The inflorescence condition rating scale used was 0: no discoloration of bract (boat) or florets; 2: 5–10% of all florets showing browning, or wilting; 3: 20–30% of all florets showing browning, wilting, or darkening of the bract; 4: 30–50% of florets showing browning, wilting, or darkening of the bract; and, 5: more than 50% of the florets showing browning, wilting, or darkening or bracts. The number of inflorescences with pale florets was recorded. 1.3. Data analysis Experiments were repeated at least once and the data of each experiment was analyzed by either the General Linear Model Procedure (GLM) or analysis of variance (ANOVA) procedure. Each treatment within an experiment had 10 or 12 inflorescences. Where possible, mean comparisons were made with the Waller-Duncan multiple range test. Statistical analysis was carried out using the SAS statistical package (SAS Institute Inc., Cary, NC). 2. Results

1. Materials and methods 2.1. Maturity and floret quality 1.1. Plant material Inflorescences were harvested from a commercial field at Waialua on the Island of Oahu, either on the day before being brought to the laboratory or on the same day. Three stages of inflorescence development were harvested: immature was 2 d before the commercial stage and had only a small knuckle on the upper side of the unopened bract; commercial stage had a pronounced orange knuckle on the upper side of the unopen bract, and, the mature stage had one opened floret and was about 2 d after the commercial stage. After sorting for uniformity, inflorescences were recut to the same stem length (55 cm), or were cut to 35 and 70 cm to determine the effect of stem length. Inflorescences were treated before packing by holding the flower stems in 1 L of various solutions for 24 h at 22 ◦ C unless otherwise indicated. Prepack treatment solutions included 5, 10, 20 and 40% (w/v) sucrose, 5 or 10% sucrose plus 200 mg L−1 8-HQC and 150 mg L−1 citric acid, STS (1 mmol L−1 silver nitrate + 4 mmol L−1 sodium thiosulfate) for 10 min and GA3 25 mg L−1 overnight. All inflorescences were then packed for 2 d in plastic-lined cartons with moistened shredded newspaper and held at 22 ◦ C. After unpacking, the stems were recut and 2 cm removed under water and the stem placed in either 1 L of distilled water or holding solutions for postharvest life evaluation at 22 ◦ C, 70–80% RH and 12 h per day florescent light (15 ± 4 mmol m−2 s−1 ). Holding solutions tested included distilled water, 10% sucrose, 200 mg L−1 8-HQC and 10 mg L−1 silver nitrate (AgNO3 ), 200 mg L−1 8-HQC, 10 mg L−1 AgNO3 and 25 ␮mol L−1 aminooxyacetic acid (AOA).

The postharvest life of mature inflorescences was 1.1–1.2 times greater than the immature and commercial harvest stage (Fig. 1A). The number of florets that opened in the immature and commercial stages of development was fewer than from inflorescences harvested at the mature stage (Fig. 1B). Mature inflorescences had a longer postharvest life and a greater number of florets also developed in the warm season than in the cool season. The percentage of inflorescences with pale florets was higher (67%) in the younger inflorecences (Fig. 1C) than in inflorescences harvested at the more mature stages (17 and 4%, respectively). The season of harvest did not influence the percentage of inflorescences with pale florets. 2.2. Stem length and maturity Stem length had a significant effect on postharvest life (Fig. 2), the longer the stem retained after harvest on mature inflorescences, the greater the postharvest life. When the stem was short (35 cm), the postharvest life of the less mature inflorescences was greater than in the more mature flowers. No significant inflorescence maturity by stem length interaction was found. 2.3. Pretreatment and holding solutions Overnight treatment of Bird-of-Paradise flowers with 20 or 40% sucrose plus 250 or 500 mg L−1 8-HQC and 150 or 300 mg L−1 citric acid did not increase postharvest life, although

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Table 1 Effect of pretreatment of Bird-of-Paradise inflorescences with 5% (w/v) sucrose overnight and wrapping the cut stems in wet sponge before packing for 2 d, 2 cm of stem removed upon unpacking and the inflorescences then held in distilled water, to determine postharvest life Treatment

Packing

Sponge

Postharvest life (day)a

Control

No packing Packed

No sponge No sponge Sponge

11.3 b 12.3 b 11.8 b

Pulsed (5% sucrose)

No packing Packed

No sponge No sponge Sponge

13.0 b 15.88 ab 16.8 a

a Means followed by the same letter within a column are not significantly different (P < 0.05, n = 10).

Fig. 1. The postharvest life (A), open florets per inflorescence (B) and percentage pale florets 1 (C) in Bird-of-Paradise inflorescences harvested at different stages of inflorescence maturity in 2 the warm season (diagonally hatched bars) and cool season (solid bars). The analysis of variance 3 of postharvest life for maturity had a P = 0.0002, season P = 0.0063 and maturity × season P = 40.0476, for number of florets the probabilities were 0.0006, <0.0001, and <0.0001, respectively, 5 and for pale florets <0.0001, 0.7171 and 0.1849, respectively. Bars with the same letter not 6 significantly different P < 0.05, n = 12.

the number of floret blooming tended to be greater in the 40% sucrose treatment than 20% sucrose (data not shown). Packing in a carton and holding for 2 d at 22 ◦ C did not increase postharvest life (Table 1) except when the inflorescences were pretreated with 5% sucrose before packing and had the stem end covered with a wet sponge. A wet sponge on the stem alone during packing did not increase postharvest life. Addition of gibberellic acid overnight to the solution prior to packing or in the holding solution similarly did not increase postharvest life (data not shown). Sodium hypochlorite (50 and 100 mg L−1 ) or 200 mg L−1 8-HQC in the holding solutions did not increase the postharvest life of Bird-of-Paradise inflorescences (data not shown). A holding solution after unpacking of 10% sucrose, 200 mg L−1 8-HQC and 10 mg L−1 AgNO3 increased postharvest life to ca. 19 d (Table 2). Aminooxyacetic acid (25 ␮mol L−1 ) in the holding solution did not increase postharvest life (Table 2). Treating inflorescences with silver thiosulfate for 10 min plus gibberellic acid overnight increased postharvest life, though sucrose plus 8-HQC and citric acid did not required holding in 10% sucrose after pack to achieve the longest postharvest life (Table 3). Treating overnight with 10% sucrose, 200 mg L−1 8-HQC and 150 mg L−1 citric acid did not increase postharvest life (Table 3), whereas inflorescences held after pack in 10% sucrose, 200 mg L−1 8-HQC and 10 mg L−1 AgNO3 had 1.2 times longer postharvest life after unpacking than the distilled water control (Table 3). Flowers treated with 10% sucrose, 200 mg L−1 8-HQC and 150 mg L−1 citric acid had the longest postharvest life, and sucrose in the holding solution increased the Table 2 Effect of different holding solution after 2 d pack on the postharvest life of Bird-of-Paradise inflorescences

Fig. 2. The effect of different stem lengths (solid bar 35 cm, hatched bar 70 cm) and 1 inflorescence maturity at harvest on the postharvest life of Bird-of-Paradise inflorescences, two packed for 2 d then held in distilled water. Analysis of variance for maturity had a P = 0.288, stem 3 length P = 0.011 and stem length by maturity P = 0.365. Bars with the same letter were not 4 significantly different P < 0.05, n = 12.

Holding solution

Postharvest life (day)a

Distilled water 10% sucrose + 200 mg L−1 8-HQC + 10 mg L−1 AgNO3 25 ␮mol L−1 AOA

14.8 b 18.6 a 14.8 b

Holding solutions included 10% sucrose, 8-hydroxyquinoline citrate (8-HQC) and silver nitrate, and aminooxyacetic acid (AOA). a Means followed by the same letter within a column are not significantly different (P < 0.05, n = 12).

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Table 3 Effect of different prepacking solutions on the postharvest life of Bird-of-Paradise. Inflorescences were treated with silver thiosulfate (1 mmol L−1 silver nitrate + 4 mmol L−1 sodium thiosulfate) for 10 min plus GA3 25 mg L−1 overnight or 10% (w/v) sucrose, 200 mg L−1 8-hydroxyquinoline citrate (8-HQC) and 150 mg L−1 citric acid overnight then packed for 2 d, 2 cm of stem was removed upon unpacking and the inflorescences placed in holding solutions of distilled water or 10% (w/w) sucrose Treatment Pretreatment

Holding solution

Distilled water Silver thiosulfate + GA3 Sucrose + 8-HQC + citric acid Distilled water Silver thiosulfate + GA3 Sucrose + 8-HQC + citric acid

Distilled water Distilled water Distilled water Sucrose Sucrose Sucrose

Postharvest life (day)a

Number of open florets

10.3 c 12.3 b 13.6 a 12.7 b 13.5 a 13.5 a

1.0c 1.0c 1.4 b 1.4 b 1.3 b 1.8a

Analysis of variance

Probability > F

Probability > F

Pulsed Holding solution Pretreatment × holding solution

0.045 0.75 0.008

0.81 0.01 0.092

a

Means followed by the same letter within a column are not significantly different (P < 0.05, n = 10).

number of open flowers (Table 3). Inflorescences treated for 6 h with 1 ␮L L−1 1-methylcyclopropene (1-MCP) did not increase postharvest life or number of open florets per inflorescence (data not shown). 3. Discussion A few days prior to harvest, the Bird-of-Paradise inflorescences are often covered by a paper or wax paper bag, wrapped with electrical tape, a wide elastic band or a plastic net sleeve installed to prevent inflorescences from opening during transportation, and hence reduce mechanical injury to the floret (Criley and Paull, 1993). Inflorescences are normally harvested in the morning by pulling the stem from the plant clump at the mature stage, characterized by the bract being split at the top, allowing the orange sepals inside the inflorescence boat to be seen (Criley and Paull, 1993). Immature inflorescences had a shorter postharvest life and this was more pronounced in the warm season than the cool season (Fig. 1A). Inflorescences harvested in the cool season tend to have a slightly longer postharvest life than inflorescences harvested in the warm season (Jaroenkit and Paull, 2003). However, if the stem was cut short (35 cm), more mature inflorescences had a shorter postharvest life (Fig. 2). More mature inflorescences on longer stems also had a greater number of florets that opened (Fig. 1B) and were less likely to be pale (Fig. 1C). The results support those of Halevy et al. (1978) in that maturity and a sugar pretreatment for 2 d does enhance flower bud opening. The results suggest that inflorescences that develop in the warm season may have greater nutrient reserves. Similarly, longer stems had greater water reserves as water uptake after harvest is limited (Jaroenkit and Paull, 2003). Generally, no leaves are left attached to the stem and the inflorescences are packed securely in the carton (Akamine, 1976). Inflorescences may be harvested a few days earlier than the commercial stage if a sugar pretreatment is used to enhance flower bud opening (Halevy et al., 1978). A treatment with 10%

sucrose, 250 mg L−1 8-HQC and 150 mg L−1 citric acid for 2 d at 22 ◦ C (Halevy et al., 1978) has been recommended. Other researchers, however, recommend pulsing Bird-of-Paradise for only 1 d with the same solution (Kofranek, 1982) and a 40% sucrose pulse for 24 h has also been recommended (Finger et al., 1999). Treatments using 20 and 40% sucrose for 2 d in our experiments did not increase postharvest life while a 5% sucrose treatment for 24 h and the use of sponge on the end of the stem during simulated shipping in a carton did increase postharvest life (Table 1). Whittaker (1993) failed to show a benefit of a 46 h-sugar treatment for Bird-of-Paradise applied a few days after harvest, though Halevy et al. (1978) reported that delaying treatment had no effect on postharvest life. The difference in response reported by Halevy et al. (1978) and Whittaker (1993) may be due to the differences in the solutions used and the high variation in the latter’s data. There is no additional increase in postharvest life, if the sucrose concentration is the pretreatment solution is raised from 10 to 25% (Halevy et al., 1978), we were also not able to show additional benefit of 20 or 40% sucrose solutions. The differences between the published results and ours could reflect differences in growing conditions, maturity of inflorescence and the stem length after harvest. Treatment of inflorescences prior to packing with various solutions has been reported to significantly increase Bird-ofParadise floret opening irrespective of the starting time of treatment, whether before or after storage, and these treatments did not affect the solution’s ability to extend postharvest life (Halevy et al., 1978) and was confirmed in this study (Table 3). However, this was not always the case, in part, due to variation between individual flowers. Dipping the stem in silver nitrate solution (1000 mg L−1 , 15 min) significantly reduces flower postharvest life, if the stems are not subsequently treated with sucrose solutions (Halevy et al., 1978). Another report indicated that the best postharvest treatment was a dip in STS for 10 min followed by holding in gibberellic acid overnight and then held in a vase solution containing sucrose, HQS and citric acid (ElSaka et al., 1995). This recommendation is reported to extend

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postharvest life from 15.5 to 38.5 d. Attempts to duplicate this report were unsuccessful (Table 3). Part of the difference may lie in the criteria use to judge the end of postharvest life that are not given by El-Saka et al. (1995). The absence of a simulated shipping treatment in that report was unlikely to explain the long postharvest life as packing only tended to slightly increase postharvest life (Table 1). Holding solution containing sucrose did increase the number of florets opened (Table 3) and a solution of sucrose, 8-HQC and AgNO3 did increase the postharvest life (Table 2). The results support the following postharvest protocol. Inflorescences should be harvested with no open florets and a pronounced orange knuckle in the upper side of the unopened bract (Fig. 1). Leaves were removed and the stem left as long as possible (Fig. 2). Inflorescences treated with 5% sucrose, or, a mixture of 10% sucrose, 250 mg L−1 8-HQC and 10 mg L−1 AgNO3 for 24 h and were then packed for up to 2 d with the stem end wrapped in a wet sponge had a longer postharvest life (Table 1). Upon unpacking, 2 cm of stem was removed and inflorescences held in distilled water or sucrose, 8-HQC and citric acid (Table 3). This protocol gave a postharvest inflorescence life of from 14 to 18 d. Acknowledgment This work was partially supported by USDA-CSREES Special Grants 96-34199-2645, 99-34199-7552 and 200334199-14041.

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References Akamine, E.K., 1976. Postharvest handling of tropical ornamental cut crops in Hawaii. HortScience 11, 125–127. Criley, R.A., Paull, R.E., 1993. Review: postharvest handling of bold tropical cut flowers Anthurium, Alpinia purpurata, Heliconia, and Strelitzia. Acta Horticult. 337, 201–211. El-Saka, M., Awad, A.E., Fahmy, B., Dowh, A.K., 1995. Trials to improve the quality of Strelitzia reginae Ait. flowers after cutting. In: Ah-Oubahao, A., El-Osmari, M. (Eds.), Postharvest Physiology, Pathology and Technology for Horticultural commodities: Recent Advances. Institute Agronomique & Veterianaire Hassan II, Agadir, Morocco, pp. 480–485. Finger, F.L., Campanha, M.M., Barbosa, J.G., Fontes, P.C.R., 1999. Influence of ethephon, silver thiosulfate and sucrose pulsing on Bird-of-Paradise vase life. Revista Brasileira de Fisiologia Vegetal 11, 119–122. Halevy, A.H., Kofranek, A.M., Besemer, S.T., 1978. Postharvest handling methods for bird of paradise flowers (Sterlitzia reginae Ait.). J. Am. Soc. Horticult. Sci. 103, 165–169. Halevy, A.H., Mayak, S., 1979. Senescence and postharvest physiology of cut flowers Part 1. Horticult. Rev. 1, 204–236. Jaroenkit, T., Paull, R.E., 2003. Postharvest handling of Heliconia, Red Ginger, and Bird-of-Paradise. HortTechnology 13, 259–266. Kofranek, A.M., 1982. Postharvest handling methods for bird of paradise flowers. In: Fifth Annual Ornamental Short Course Proceedings, p. 41. Paull, R.E., Chantrachit, T., 2001. Benzyadenine and the vase life of tropical ornamentals. Postharvest Biol. Technol. 21, 303–310. Sacalis, J.N., 1993. Cut Flowers: Prolonging Freshness, Postproduction Care & Handling, second ed. Ball Publishing, Batavia, IL, USA. Whittaker, J.M. 1993. Postharvest Handling Procedure for Jamaican Grown Cut Flowers, Master Thesis. University of Florida, Gainsville, FL.