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Pre- and post-production characteristics of Coprosma as influenced by temperature, irradiance, and nutrient treatments
Scientia Horticulturae 145 (2012) 46–51
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Pre- and post-production characteristics of Coprosma as influenced by temperature, irradiance, and nutrient treatments Jeong Hong a , Jeung Keun Suh b,∗ a b
Department of Horticulture, Division of Environmental & Life Science, Seoul Women’s University, Nowon-Ku, Seoul, Republic of Korea Department of Environment Horticulture, Dankook University, Cheonan, Chungnam, Republic of Korea
a r t i c l e
i n f o
Article history: Received 6 February 2012 Received in revised form 4 July 2012 Accepted 12 July 2012 Keywords: Coprosma ‘Coppershine’ Carbohydrate analysis Fertilizer application Foliar analysis Forcing temperature Irradiance level Interior keeping quality Leaf drop
a b s t r a c t The genus Coprosma has the potential to be used as a house and garden plant throughout the world. Coprosma ‘Coppershine’ was selected to study the effect of nutrition and irradiance on Coprosma growth and development. Post-production characteristics were also evaluated by placing greenhouse grown plants in 12.5 cm pots directly into a simulated interior environment (SIE). The amount of leaf abscission was lowest in the SIE when plants received 2 g of controlled release fertilizer (CRF). Our data show that the tissue nitrogen (N) concentration should be higher than 4% to prevent leaf abscission of C. ‘Coppershine’. Increased fresh and dry weights combined with no leaf abscission after 18 days under SIE using 2 g CRF demonstrates that a steady availability of nutrients is required. More leaves abscissed when plants were grown at high temperature (21 ◦ C) and under the highest irradiance (316 mol m−2 s−1 ) as compared to plants grown at low temperature (15.5 ◦ C) and mid level of irradiance (218 mol m−2 s−1 ). The tissue concentration of calcium (Ca) in the mid leaves may also be associated with the leaf abscission and reduced fructose was associated with low drop of leaves. This is the first report that post production leaf abscission in C. ‘Coppershine’ can be reduced by growing with an increased fertilizer level at high temperature. This response is correlated with high tissue N concentration responding to CRF treatment under a SIE. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The genus Coprosma, Rubiaceae, comprises over 90 species and is endemic to New Zealand, Australia, and Polynesia (Wilson, 1979; Beuzenberg, 1983). Plants in the genus are shrubs or small trees with shiny or variegated leaves. Coprosma has been commercialized in Europe, however, it has not widely known to the public either as a landscape or house plant. Information on the culture of Coprosma as an outdoor ornamental plant or on the performance as an indoor plant is not available. Extensive research has been carried out on Ficus benjamina L. to study foliage abscission or leaf loss when plants grown under full sun conditions were transferred directly to a SIE without acclimatization (Steinkamp et al., 1991). Acclimatization of plants when placed under interior light levels was also related to fertilization rates which affected leaf morphology structure, and abscission (Johnson et al., 1979). Leaf abscission was severe when plants grown under full sun and receiving high rates of nitrogen fertilization were transferred to interior conditions without acclimatization
∗ Corresponding author. Tel.: +82 11 436 3642; fax: +82 41 553 6971. E-mail address: [email protected] (J.K. Suh). 0304-4238/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scienta.2012.07.013
(Conover and Poole, 1975a,b; Turner et al., 1987). The level of irradiance for optimum growth may differ by crop. The ornamental value of Pachira aquatica Aubl. (Li et al., 2009) was significantly improved by growing plants under intermediate irradiance between 285 and 350 mol m−2 s−1 . When Chamaedorea elegans Mart. plants were treated at different irradiance levels and fertilizer rates, total soluble carbohydrate in leaves was higher when grown at an intermediate irradiance (306 mol m−2 s−1 ) and the starch concentration was affected by irradiance and fertilizer level (Reyes et al., 1996). During the production of many foliage plants, high levels of nitrogen should not be applied before placement indoors (Conover et al., 1991). Controlling mechanisms that are involved in leaf abscission when plants were transferred to a SIE has not been elucidated in detail; possible relationships may exist with the tissue concentration of calcium (Ca) which may inhibit ethylene induced abscission in bean petiole (Poovaiah and Leopold, 1973) and abscisic acid induced ethylene evolution of leaf abscission in Radermachera sinica L (Dunlap et al., 1991). Sun grown F. benjamina had more carbohydrates than those grown under shade and increased N lowered the carbohydrate reserves (Milkes et al., 1970). Carbohydrate reserves accumulated in plants at high irradiance provided energy for plants to adapt to a low-irradiance environment Megaleranthis
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saniculifolia (Reyes et al., 1996; Veneklaas and den Ouden, 2005), although there is no direct relationship between changes in carbohydrate in the leaf blade during defoliation with a chemical defoliant (Hall and Lane, 1952). Cultural information for C. ‘Coppershine’ on the optimum levels of irradiance, temperature, and nutrition for successful greenhouse production and the post-production keeping quality in interior environments is currently unavailable. When grown outdoors C. ‘Coppershine’ should be grown in full sun to retain leaf color and avoid leaf abscission (Metcalf, 1987). Therefore, it is expected that C. ‘Coppershine’ plants grown under full sun may lose leaves when transferred to low light environments as reported for other foliage plants (Chen et al., 2005; Li et al., 2009; Turner et al., 1987). English ivy (Hedera helix L.) grown under low irradiance and low fertility produced good quality plants when placed under SIE which resulted in better acclimatization (Pennisi et al., 2005). Research was initiated to investigate the effect of controlled release and liquid fertilizer, irradiance, and temperature treatments on growth during greenhouse forcing and subsequent keeping quality when plants were moved to SIE without preacclimatization treatment. Changes in carbohydrates and foliar mineral content on the keeping quality of C. ‘Coppershine’ were also evaluated. 2. Materials and methods 2.1. Plant material and greenhouse conditions Five-cm long stem tip cuttings of C. ‘Coppershine’ were propagated in Metro Mix 200 in a mist bench (12 s mist every 15 min from 08:00 h for 16 h) in a greenhouse maintained at 24 ◦ C with heat pads. One week after transplanting rooted cuttings into 12.5 cm pots filled with a growing medium composed of soil:perlite:peat moss (1:1:1, vol%), controlled release fertilizer (CRF) (Osmocote 14N–6P–8.2K, Marysville, OH, USA) was applied on the surface of growing medium. Additionally, plants were fed weekly with 200 mg/L N from a 20N–8.6P–11.7K (Peters 20-20-20 fertilizer, Marysville, OH, USA) water soluble fertilizer, and grown at 8/16 h day/night cycle at 21 ◦ C/16 ◦ C, respectively, under a natural day length and irradiance levels ranging from 240 to 490 mol m−2 s−1 using high irradiance discharge (HID) lamps from 08:00 to 20:00 h. 2.2. Effect of controlled fertilizer (CRF) and liquid fertilizer (LF) on plant growth and post-production quality in a simulated interior environment (SIE) (Expt. 1) 2.2.1. Plant growth Plants received CRF at the rates of 0, 2, and 4 g per pot and also LF at 200 and 400 mg/L in a 3 CRF × 2 LF factorial design. The first LF was given one week after pinching. For fresh and dry weight collection, the entire shoots from 3 plants per treatment were sampled 50 days after the first LF treatment. Dry weight was determined following exposure at 75 ◦ C under a forced air-dryer for 3 days. There were 10 plants per treatment and the number of shoots longer than 5 cm from the main shoot were counted. 2.2.2. Foliar macro- and micro-elements and carbohydrate analyses and assessment of leaf loss To investigate foliar elements, soluble carbohydrate extracted with 80% ethanol and leaf abscission, we collected leaf samples at day zero (day 0) and from plants following a SIE 11 days later. The SIE conditions were maintained at constant 21 ◦ C in the SIE at an irradiance of 20 mol m−2 s−1 using cool white florescent and incandescent light for 12 h. Humidity varied between 50 and 75%. Fully developed leaves were collected from mid-way up the stem in duplicate for foliar analysis as described (Roh et al., 2012).
Fig. 1. Coprosma, ‘Coppershine’ in 12.5 cm pot. Leaf from the main shoot as indicated with solid arrow and from the lateral shoots as indicated with dotted arrow is indicated. Leaves intact from the main shoot (Mi) and the lateral shoot (Li) and abscised from the main shoot (Ma) and the lateral shoot (La) are indicated.
For soluble carbohydrate analysis extracted with 80% ethanol, samples of mature leaves were collected in triplicate and analyzed as described previously (Lee and Roh, 2011). The number of leaves dried from the main shoot and lateral shoots were recorded on day 11 and on day 18 during evaluation under SIE. Leaves from the main shoot were larger than those from the lateral shoots, and absence of the abscised leaf scars from the node on the main shoots were examined to confirm the leaves dropped from the main shoot (Fig. 1). 2.2.3. Temperature, irradiance, and controlled release fertilizer treatment on growth and post-harvest physiology (Expt. 2) To investigate the effect of temperature, irradiance and fertilizer on plant growth, 5 cm long cuttings were collected from the stock plants as described above. We placed 15 rooted stem-tip cuttings planted into 12.5 cm pots per treatment were placed into two greenhouse sections maintained at 23 ◦ C/21 ◦ C and 21 ◦ C/15.5 ◦ C, day/night. Experimental treatments was carried out in a factorial design; 3 CRF (0, 2, or 4 g of CRF applied on the surface of the growing medium at planting) × 2 greenhouse temperatures × 3 supplementary light irradiance (no supplementary irradiance and at 218 and 316 mol m−2 s−1 from HID lamps as indicated above). Plants were fed weekly with 200 mg/L N from a 20N–8.6P–11.7K water soluble fertilizer. Plant height, plant width at one-half of the plant’s height, and the number of nodes were recorded 65 days after the initiation of treatments. From three median plants in height, leaves and shoots that were formed during treatments were collected for fresh and dry weight measurement following the sample drying method previously described. Six uniform plants representing the treatment
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Table 1 Growth of Coprosma, ‘Coppershine’ as influenced by controlled release fertilizer (CRF) and liquid fertilizer (LF) (Expt. 1). CRF
LF
FW (g)
DW (g)
Length (cm) of 5 longest shoots
0
200 400
36.2 69.3
0.75 1.98
1.8 4.4
2
200 400
64.7 61.9
1.73 2.45
3.3 4.8
4
200 400
68.9 67.7
2.62 3.17
4.8 4.8
Level of significancea CRF Linear Quadratic
*** *
** ns
*** ns
LF
**
**
***
*
***
*
11.8
0.28
0.87
CRF Linear × LF b
hsd at P < 0.05 or P < 0.01 a b
Weight and shoot length
Non-significant (ns) and significant difference at 5% (*), 1% (**), and 0.1% *(***), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.05 for the fresh weight and length and P < 0.01 for dry weight.
were selected and placed in a SIE 65 days after the initiation of treatments. The number of leaves abscissed in 7 days and the total number of leaves abscissed during 33 days of SIE was recorded from each plant. 2.3. Statistical analysis Data were subjected to analysis of variance and polynomial analysis was performed using general linear model. Linear and quadratic orthogonal contrasts were computed for the amount of CRF and the linear term of the interaction with other main variables is presented. Means were compared by Tukey’s honesty significant difference (hsd test) at P < 0.05 or P < 0.01. 3. Results 3.1. Effects of controlled fertilizer (CRF) and liquid fertilizer (LF) treatment on plant growth and post-production quality under a simulated interior environment (SIE) Fresh weight, dry weight and shoot length of the 5 longest shoots of plants which received 200 mg/L N LF was significantly less and shorter than the 64.7 g FW, 1.73 g DW, and 3.3 cm, respectively, which received 2 g CRF with 200 mg/L LF (Table 1). When plants received 200 mg/L N LF, the number of leaves abscissed by day 11 under SIE was the greatest; 18 leaves from the main shoot and 13 leaves from the lateral shoots (Table 2). The number was reduced to less than 6.8 and 4.0 when plants received 400 mg/L N LF. One or no leaves abscissed when plants received 2 g or 4 g CRF, regardless of LF concentration After 18 days, plants under SIE abscissed 24.7 leaves when provided with 200 mg/L LF. 3.2. Foliar macro- and micro-element levels, carbohydrate analyses, and assessment of leaf abscission Nitrogen (N) concentration (2.7%) in leaves formed in the middle of the stem (mid leaves) and receiving only 200 mg/L LF was the lowest, among all treatments (Table 3). The concentration of other elements; phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and manganese (Mn) also showed similar trends. The concentration of N and P was lower than the suggested normal range, K and Ca was within the suggested normal range, and Mg and Mn was higher than the suggested normal range (JR Peters Laboratory,
Allentown, PA, USA). The concentration of micro-elements; iron (Fe), zinc (Zn), and molybdenum (M) was within the suggested normal range; 60–200 ppm for Fe, 30–150 ppm for Zn, and 0.5–5.0 ppm for Mn. However, the concentration of boron (B), ranging from 15.5 mg kg−1 to 21.5 mg kg−1 , was lower than suggested normal ranges. The concentration of micro-elements of leaves that received only 200 mg/L N was generally lower than those that received CRF with LF treatments. The concentration of glucose was not affected by irradiance and CRF (Table 4). The concentration of fructose when plants received 4 g CRF and 400 mg/L N was the lowest when sampled on day 0 after SIE and again following 11 days at SIE. The decrease in fructose concentration following 11 days in an SIE regardless of CRF and LF concentration was evident. Although the concentration of glucose in leaves subjected to SIE that received 200 mg/L LF was 6.98 mg/g.fw, the concentration was not significantly affected by CRF, LF, and SIE. Sucrose concentration increased from 1.75 mg/g fw (400 mg/L LF at day 0 SIE) to 2.47 mg/g fw following 11 days at SIE. 3.3. Temperature, irradiance, and controlled release fertilizer (CRF) treatment on growth and post-harvest performance Plants were the tallest (29.8 cm) when they received supplementary irradiance of 316 mol m−2 s−1 and plant width and the fresh weight and dry weight also showed similar trends as those observed for the total plant height. (Data not presented.) In general, the plants were taller when grown at 21 ◦ C than those at 15.5 ◦ C and shorter when they received 4 g CRF, regardless of temperature and irradiance level. The number of nodes was less than 11.2 when plants were grown at 15.5 ◦ C under ND regardless of CRF treatment. When plants were grown at 21 ◦ C without receiving CRF, the number of leaves abscised on day 7 of SIE ranged from 1.3 leaves (ND + 218 mol m−2 s−1 ) to 1.7 leaves (ND + 316 mol m−2 s−1 ) was significantly less than the numbers abscissed, more than 2.5 when grown at 15.5 ◦ C (Table 5). When plants received 2 g or 4 g of CRF, the number of leaves abscised was significantly less than from plants that were grown without CRF. The number of leaves dropped after 7 days of SIE was less than 0.2 when plants were grown under the highest irradiance of 316 mol m−2 s−1 with 4 g CRF, a few leaves abscissed regardless of production temperature and CRF treatments. At 33 days of SIE, significantly fewer leaves abscissed if plants received 4 g CRF, regardless of production temperature and
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Table 2 The number of leaves dropped 11 and 18 days after simulated interior environment (SIE) treatment (Expt. 1). Treatmenta
Number of leaves dropped
Nutrition
Day 11b
Day 18 (total)
CRF
LF
Main shoot
Lateral shoots secondary
0
200 400
18.0 5.3
13.0 4.0
24.7 9.3
2
200 400
0.0 0.0
0.0 0.0
4.7 0.7
4
200 400
0.0 0.0
0.0 0.0
0.0 0.0
Level of significancec CRF Linear Quadratic
** **
** *
** **
LF
*
**
**
CRF Linear × LF
**
**
**
hsd, P < 0.01
1.28
2.36
2.84
a
Controlled release fertilizer (CRF) and liquid fertilizer (LF). Number of days at a ASIE. Linear (Lin) and quadratic (Quad) effect; non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01. b c
irradiance treatments. More leaves abscissed when plants were grown at high temperature (21 ◦ C) and under the highest irradiance (316 mol m−2 s−1 ) as compared to plants grown at low temperature (15.5 ◦ C) and mid level of irradiance (218 mol m−2 s−1 ).
4. Discussion Post-production quality of many foliage plants, especially F. benjamina has been investigated extensively and plants grown under sun and high fertilization required “acclimatization” to increase the quality and help leaf retention when they are moved to low irradiance interior environment. Without proper acclimatization, severe leaf drop will occur. However, the effect of irradiance, temperature, and nutrition on the growth of Coprosma as a greenhouse crop, and leaf abscission when placed in a SIE is not known.
4.1. Controlled fertilizer (CRF) and liquid fertilizer (LF) treatment on plant growth and post-production quality during a simulated interior environment (SIE) Reduced biomass as quantified by the fresh and dry weight when C. ‘Coppershine’ plants received only 200 mg/L N LF (0 g CRF + 200 mg/L LF) may be responsible for increased leaf loss when plants were placed in a SIE. Plants that received CRF treatments had increased fresh and dry weight and did not drop any leaves from the main shoot. This suggests that a constant supply of nutrients from CRF during greenhouse culture resulted in higher metabolic reserves when plants were placed in a SIE (Li et al., 2009) and thus, played an important role in leaf retention. The significant loss of leaves was also correlated with a low tissue N concentration in the leaves collected from mid-portion of the shoots after 11 days of SIE when leaf abscission became significant and at 15 days at
Table 3 The concentration of macro-and micro-elements of foliar analysis of C. ‘Coppershine’ collected from plants treated with controlled release fertilizer (CRF) and liquid fertilizer (LF) treatment during greenhouse forcing (Expt. 1). Treatmenta
Concentration
CRF
LF
N (%)
P (%)
K (%)
Ca (%)
Mg (%)
Mn (ppm)
0 2.0 4.0 0 2.0 4.0
200 200 200 400 400 400
2.7 3.4 4.0 4.0 5.0 4.5
2.75 3.05 3.80 3.65 3.60 3.75
2.15 2.25 2.40 2.50 2.70 2.65
0.90 1.45 1.20 1.40 1.45 1.55
2.20 2.20 2.45 2.60 3.10 3.35
260 314 292 309 311 275
ns *
** **
** **
ns **
** **
** **
* 0.51
** 0.48
ns 0.08
** 0.14
ns 0.37
ns 23.5
Level of significanceb CRF Linear LF CRF Linear × LF hsd at P < 0.05 or P < 0.01c a b c
Controlled release fertilizer (CRF) and liquid fertilizer (LF). Non-significant (ns) and significant difference at 5% (*)and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.05 for N or P < 0.01 and for all other elements.
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Table 4 The effect of irradiance, forcing temperature, and controlled release fertilizer (CRF) and liquid fertilizer (LF) during forcing and the duration of simulated interior environment (SIE) on soluble carbohydrates (Expt. 2). Treatment CRF
Soluble carbohydrate (mg/g fw) LF
Fructose
Glucose SIE
SIE
0
200 400 200 400 200 400
2 4 Level of significancea CRF Linear Quadratic LF Days at SIE CRF – linear × LF CRF – linear × SIE CRF – linear × LF SAE × LF CRF – linear × LF × SIE hsd at P < 0.01 a
Sucrose SIE
0
11
0
11
0
11
4.01 1.75 2.82 2.37 2.18 0.91
2.37 1.69 1.08 0.89 0.75 0.74
6.98 4.75 5.29 5.32 5.82 4.96
5.13 4.86 4.43 5.09 4.42 5.10
2.12 1.75 2.27 2.29 1.89 2.01
2.34 2.47 2.19 3.11 1.99 2.32
ns ns ns ns ns ns ns ns ns 2.24
** ** ** ** ** ns ** ns ns 0.94
** ns ns ** ns * ns ns ns 0.36
Non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01.
SIE, was lower than 2.7%, suggesting that tissue N concentration must be higher than 3.4% (2 g CRF + 200 mg/L N LF) to 4.0% (0 g CRF + 400 mg/L N LF) to prevent leaf loss. It is clear that nutrition should be steadily available to C. ‘Coppershine’ plants using 2–4 g CRF resulting in the increase of nitrogen tissue concentration higher than 4% to prevent leaf drop. This is the first report that leaf loss is reduced when leaf tissue
concentration of N is maintained at a high level following a steady supply of high fertilizer treatments. Numerous reports on Ficus reported that leaf loss was increased by high N fertilizer treatments (Johnson et al., 1979; Poole and Conover, 1982). The response to fertilizer in acclimatization may depend on the crop since fertilizer treatment using controlled release fertilizer during production of Dracaena marginata Lam. did not affect interior performance
Table 5 The number of leaves dropped in 7 days and the total number of leaves dropped during 33 days when plants were evaluated under a simulated interior environment (SIE) as influenced by irradiance, forcing temperature, and controlled release fertilizer (CRF) treatment. Treatment
Number of leaves dropped
Irradiance (mol m−2 s−1 )
Temp ( ◦ C)
CRF (g)
7 days under SIE
33 days under SIE
ND
15.5
0 2 4 0 2 4
2.7 1.2 0 1.6 1.1 0
15.0 9.3 4.3 17.8 13.2 7.3
0 2 4 0 2 4
2.5 1.8 0 1.2 1.4 0
17.3 14.7 4.7 15.8 13.5 7.5
0 2 4 0 2 4
2.7 2.1 0.2 1.7 1.0 0.2
17.7 17.2 6.7 16.0 16.2 9.3
ns ** ** * ns ** * 0.72
ns ** ** * ns ** * 4.83
21
ND + 218
15.5
21
ND + 316
15.5
21
Level of significancea Irradiance (Irrad.) – linear Temperature (Temp.) CRF Irrad. – linear × Temp. Irrad. – linear × CRF Temp. × CRF Irrad. – linear × Temp. × CRF hsd at P < 0.01 a
Non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01.
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(Conover and Poole, 1975b). Reduced leaf drop in C. ‘Coppershine’ in plants grown with an increased fertilizer and high temperature is unique and different from findings in F. benjamina (Pennisi et al., 2005; Turner et al., 1987) and in Epipremnum aureum (Reyes et al., 1990). As expected, supplemented irradiance was not effective in reducing leaf drop.
supply of nutrition from the CRF is placed directly into a SIE without acclimatization. The data show that tissue nitrogen content of the mature leaves at the main shoot should be higher than 4% corresponding to 2 g of CRF treatment in a 12.5 pot. Whether the decrease in fructose is associated with leaf drops requires further investigation.
4.2. Foliar macro- and micro-elements and carbohydrate analyses and assessment of leaf loss
Acknowledgements
The tissue concentration of calcium (Ca) in the mid leaves may be associated with leaf loss, if physiological responses to Ca to inhibit ethylene induced abscission in bean petiole are similar (Poovaiah and Leopold, 1973). The tissue concentration of potassium (K), magnesium (Mg) (Poovaiah and Leopold, 1973), and phosphorus (P), and manganese (Mn) may not be associated with leaf loss and N, phosphorus (P), and K not with fruit abscission in Citrus sinensis [L.] Osbeck) (Ruiz et al., 2001). The tissue concentration of micro-elements did not differ significantly (data not presented) and may not be associated with leaf loss. The concentration of soluble glucose in tissue was not affected by irradiance and CRF (Table 4). The low concentration of fructose when plants received 4 g CRF and 400 mg/L N may be related to the reduced leaf drop. Is the reduced fructose associated with reduced leaf abscission in C. ‘Coppershine’? Application of exogenous fructose applied to plants prior to placing plants under a SIE and the abscisic acid (ABA) induced ethylene evolution on leaf abscission (Dunlap et al., 1991) should be investigated, although analysis of ethylene from large intact Coprosma plants may not be easy. If leaf drop is similar to fruitlet abscission, the sucrose and free reducing sugars should be reduced in C. ‘Coppershine’ as reported in the peel of the fruitlet (Citrus sinensis) (Ruiz et al., 2001). Hall and Lane (1952) reported that there is no relationship between soluble carbohydrates in the leaf blade and percentage of leaf defoliation in cotton responding to a defoliant chemical. However, in leaves of Arabidopsis thaliana (Izumi and Ishida, 2011), a remarkable accumulation of carbohydrates, glucose and fructose was observed in late senescent leaves at 10 days after bolting. 4.3. Temperature, irradiance, and controlled release fertilizer (CRF) treatment on growth and post-harvest physiology The interaction of temperature and CRF on the post-harvest quality as judged by leaf abscission was significant, while irradiance levels had no effect. The insignificant effect of irradiance on leaf abscission of C. ‘Coppershine’ is also unique as compared to the reports in F. benjamina as reviewed by Steinkamp et al. (1991). The irradiance level investigated in this study under greenhouse conditions may not be considered high, but is comparable to the intermediate irradiance (285 and 350 mol m−2 s−1 ) which increased the ornamental value of Pachira aquatica Aubl. (Li et al., 2009). Although leaf abscission is affected by irradiance and temperature during the greenhouse production phase, the most significant effect on leaf abscission is again correlated with the level of nutrition, since significantly fewer leaves abscissed when plants received 2–4 g CRF is observed, regardless of production temperature and irradiance treatments. 5. Conclusions This is the first report that leaf abscission is significantly reduced when C. ‘Coppershine’ grown in the greenhouse with a constant
Careful reading and constructive comments made by two anonymous reviewers during the review processes and improvement on usage of English and technical comments by G. Wulster, Rutgers University, are greatly appreciated. References Beuzenberg, E.J., 1983. Contribution to a chromosome atlas of the New Zealand Flora 24 Coprosma (Rubiaceae). New Zealand. J. Bot. 21, 9–12. Chen, J., Wang, Q., Henny, R.J., McConnell, D.B., 2005. Response of tropical foliage plants to interior low light conditions. Acta Hort. 669, 51–56. Conover, C.A., Poole, R.T., 1975a. Acclimatization of tropical trees for interior use. HortScience 10, 600–601. Conover, C.A., Poole, R.T., 1975b. Influence of shade and fertilizer levels on production and acclimatization of Dracaena marginata. Fl. St. Hort. Sci. 1975, 606–608. Conover, C.A., Poole, R.T., Henley, R.W., 1991. Light and fertilizer recommendations for the interior maintenance of acclimatized foliage plants. University of Florida. IFAS CFREC-A Research Report RH-91-97. Dunlap, J.R., Wang, Y.T., Skaria, A., 1991. Hormonal interactions regulating leaf abscission in Radermachera sinica L. HortScience 26, 709. Hall, W.C., Lane, H.C., 1952. Compositional and physiological changes associate with chemical defoliation of cotton. Plant Plysiol. 27, 754–768. Izumi, M., Ishida, H., 2011. The changes of leaf carbohydrate contents as a regulator of autophagic degradation of chloroplasts via rubisco-containing bodies during leaf senescence. Plant Signal. Behav. 6, 685–687. Johnson, C.R., Krantz, J.K., Joiner, J.N., Conover, C.A., 1979. Light compensation pint and leaf distribution of Ficus benjamina as affected by light intensity and nitrogen–potassium nutrition. J. Am. Soc. Hort. Sci. 104, 335–338. Lee, J.S., Roh, M.S., 2011. Carbohydrate changes during flower senescence of the Easter lily (Lilium longiflorum Thunb.). Acta Horticult. 900, 295–300. Li, Q., Deng, M., Chen, J., Henny, R.J., 2009. Effects of light intensity and paclobutrazol on growth and interior performance of Pachira aquatica Aubl. HortScience 44, 1291–1295. Metcalf, L.J., 1987. The Cultivation of New Zealand Trees and Shrubs. Reed Methuen Publishers Ltd., Auckand, New Zealand, 346 p. Milkes, R.R., Joiner, J.N., Carard, L.A., Conover, C.A., Tjia, B., 1970. Influence of acclimization on carbohydrate production and translocation of Ficus benjamina L. J. Am. Soc. Hort. Sci. 104, 410–413. Pennisi, S.V., van Iersel, M.W., Burnett, S.E., 2005. Photosynthetic irradiance and nutrition effects on growth of English Ivy in subirrigation systems. HortScience 40, 1740–1745. Poole, R.T., Conover, C.A., 1982. Influence of cultural conditions on simulated shipping of Ficus benjamina L. Proc. Fl. St. Hort. Soc. 95, 172–173. Poovaiah, B.W., Leopold, A.C., 1973. Inhibition of abscission by calcium. Plant Physiol. 51, 848–851. Reyes, T., Chase, A.R., Poole, R.T., 1990. Effect of nitrogen level and light intensity on growth of Epipremnum aureum. Proc. Fl. St. Hort. Soc. 103, 176–178. Reyes, T., Nell, T.A., Barrett, J.E., Conover, C.A., 1996. Irradiance level ad fertilizer rate affect acclimatization of Chamaedorea elegans Mart. HortScience 31, 839–842. Roh, M.S., Bauhan, G.R., Huda, M.S., 2012. Physical and chemical properties of biobased resins containing chicken feather fibers. Hort. Environ. Biotechnol. 53, 72–80. Ruiz, R., Carcia-Lois, A., Monerri, C., Guardiola, J.L., 2001. Carbohydrate availability in relation to fruitlet abscission in Citrus. Ann. Bot. 87, 805–812. Steinkamp, K., Conover, C.A., Poole, R.T. 1991. Acclimatization of Ficus benjamina: A review. University of Florida, CFREC – A research report RH-91-5. Turner, T.A., Reed, D.W., Morgan, D.L., 1987. A comparison of light acclimatization methods for reduction of interior leaf drop in Ficus spp. J. Environ. Hort. 5 (3), 102–104. Veneklaas, E.J., den Ouden, F., 2005. Dynamics of non-structural carbohydrates in two Ficus species after transfer to deep shade. Environ. Expt. Bot. 54, 148–154. Wilson, R.D., 1979. Chemotaxonomic studies in the Rubiaceae 1. Methods for the identification on hybridization in the genus Coprosma J.R. et G. Forst. using flavonoids. New Zealand J. Bot. 17, 113–116.
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Pre- and post-production characteristics of Coprosma as influenced by temperature, irradiance, and nutrient treatments Jeong Hong a , Jeung Keun Suh b,∗ a b
Department of Horticulture, Division of Environmental & Life Science, Seoul Women’s University, Nowon-Ku, Seoul, Republic of Korea Department of Environment Horticulture, Dankook University, Cheonan, Chungnam, Republic of Korea
a r t i c l e
i n f o
Article history: Received 6 February 2012 Received in revised form 4 July 2012 Accepted 12 July 2012 Keywords: Coprosma ‘Coppershine’ Carbohydrate analysis Fertilizer application Foliar analysis Forcing temperature Irradiance level Interior keeping quality Leaf drop
a b s t r a c t The genus Coprosma has the potential to be used as a house and garden plant throughout the world. Coprosma ‘Coppershine’ was selected to study the effect of nutrition and irradiance on Coprosma growth and development. Post-production characteristics were also evaluated by placing greenhouse grown plants in 12.5 cm pots directly into a simulated interior environment (SIE). The amount of leaf abscission was lowest in the SIE when plants received 2 g of controlled release fertilizer (CRF). Our data show that the tissue nitrogen (N) concentration should be higher than 4% to prevent leaf abscission of C. ‘Coppershine’. Increased fresh and dry weights combined with no leaf abscission after 18 days under SIE using 2 g CRF demonstrates that a steady availability of nutrients is required. More leaves abscissed when plants were grown at high temperature (21 ◦ C) and under the highest irradiance (316 mol m−2 s−1 ) as compared to plants grown at low temperature (15.5 ◦ C) and mid level of irradiance (218 mol m−2 s−1 ). The tissue concentration of calcium (Ca) in the mid leaves may also be associated with the leaf abscission and reduced fructose was associated with low drop of leaves. This is the first report that post production leaf abscission in C. ‘Coppershine’ can be reduced by growing with an increased fertilizer level at high temperature. This response is correlated with high tissue N concentration responding to CRF treatment under a SIE. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The genus Coprosma, Rubiaceae, comprises over 90 species and is endemic to New Zealand, Australia, and Polynesia (Wilson, 1979; Beuzenberg, 1983). Plants in the genus are shrubs or small trees with shiny or variegated leaves. Coprosma has been commercialized in Europe, however, it has not widely known to the public either as a landscape or house plant. Information on the culture of Coprosma as an outdoor ornamental plant or on the performance as an indoor plant is not available. Extensive research has been carried out on Ficus benjamina L. to study foliage abscission or leaf loss when plants grown under full sun conditions were transferred directly to a SIE without acclimatization (Steinkamp et al., 1991). Acclimatization of plants when placed under interior light levels was also related to fertilization rates which affected leaf morphology structure, and abscission (Johnson et al., 1979). Leaf abscission was severe when plants grown under full sun and receiving high rates of nitrogen fertilization were transferred to interior conditions without acclimatization
∗ Corresponding author. Tel.: +82 11 436 3642; fax: +82 41 553 6971. E-mail address: [email protected] (J.K. Suh). 0304-4238/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scienta.2012.07.013
(Conover and Poole, 1975a,b; Turner et al., 1987). The level of irradiance for optimum growth may differ by crop. The ornamental value of Pachira aquatica Aubl. (Li et al., 2009) was significantly improved by growing plants under intermediate irradiance between 285 and 350 mol m−2 s−1 . When Chamaedorea elegans Mart. plants were treated at different irradiance levels and fertilizer rates, total soluble carbohydrate in leaves was higher when grown at an intermediate irradiance (306 mol m−2 s−1 ) and the starch concentration was affected by irradiance and fertilizer level (Reyes et al., 1996). During the production of many foliage plants, high levels of nitrogen should not be applied before placement indoors (Conover et al., 1991). Controlling mechanisms that are involved in leaf abscission when plants were transferred to a SIE has not been elucidated in detail; possible relationships may exist with the tissue concentration of calcium (Ca) which may inhibit ethylene induced abscission in bean petiole (Poovaiah and Leopold, 1973) and abscisic acid induced ethylene evolution of leaf abscission in Radermachera sinica L (Dunlap et al., 1991). Sun grown F. benjamina had more carbohydrates than those grown under shade and increased N lowered the carbohydrate reserves (Milkes et al., 1970). Carbohydrate reserves accumulated in plants at high irradiance provided energy for plants to adapt to a low-irradiance environment Megaleranthis
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saniculifolia (Reyes et al., 1996; Veneklaas and den Ouden, 2005), although there is no direct relationship between changes in carbohydrate in the leaf blade during defoliation with a chemical defoliant (Hall and Lane, 1952). Cultural information for C. ‘Coppershine’ on the optimum levels of irradiance, temperature, and nutrition for successful greenhouse production and the post-production keeping quality in interior environments is currently unavailable. When grown outdoors C. ‘Coppershine’ should be grown in full sun to retain leaf color and avoid leaf abscission (Metcalf, 1987). Therefore, it is expected that C. ‘Coppershine’ plants grown under full sun may lose leaves when transferred to low light environments as reported for other foliage plants (Chen et al., 2005; Li et al., 2009; Turner et al., 1987). English ivy (Hedera helix L.) grown under low irradiance and low fertility produced good quality plants when placed under SIE which resulted in better acclimatization (Pennisi et al., 2005). Research was initiated to investigate the effect of controlled release and liquid fertilizer, irradiance, and temperature treatments on growth during greenhouse forcing and subsequent keeping quality when plants were moved to SIE without preacclimatization treatment. Changes in carbohydrates and foliar mineral content on the keeping quality of C. ‘Coppershine’ were also evaluated. 2. Materials and methods 2.1. Plant material and greenhouse conditions Five-cm long stem tip cuttings of C. ‘Coppershine’ were propagated in Metro Mix 200 in a mist bench (12 s mist every 15 min from 08:00 h for 16 h) in a greenhouse maintained at 24 ◦ C with heat pads. One week after transplanting rooted cuttings into 12.5 cm pots filled with a growing medium composed of soil:perlite:peat moss (1:1:1, vol%), controlled release fertilizer (CRF) (Osmocote 14N–6P–8.2K, Marysville, OH, USA) was applied on the surface of growing medium. Additionally, plants were fed weekly with 200 mg/L N from a 20N–8.6P–11.7K (Peters 20-20-20 fertilizer, Marysville, OH, USA) water soluble fertilizer, and grown at 8/16 h day/night cycle at 21 ◦ C/16 ◦ C, respectively, under a natural day length and irradiance levels ranging from 240 to 490 mol m−2 s−1 using high irradiance discharge (HID) lamps from 08:00 to 20:00 h. 2.2. Effect of controlled fertilizer (CRF) and liquid fertilizer (LF) on plant growth and post-production quality in a simulated interior environment (SIE) (Expt. 1) 2.2.1. Plant growth Plants received CRF at the rates of 0, 2, and 4 g per pot and also LF at 200 and 400 mg/L in a 3 CRF × 2 LF factorial design. The first LF was given one week after pinching. For fresh and dry weight collection, the entire shoots from 3 plants per treatment were sampled 50 days after the first LF treatment. Dry weight was determined following exposure at 75 ◦ C under a forced air-dryer for 3 days. There were 10 plants per treatment and the number of shoots longer than 5 cm from the main shoot were counted. 2.2.2. Foliar macro- and micro-elements and carbohydrate analyses and assessment of leaf loss To investigate foliar elements, soluble carbohydrate extracted with 80% ethanol and leaf abscission, we collected leaf samples at day zero (day 0) and from plants following a SIE 11 days later. The SIE conditions were maintained at constant 21 ◦ C in the SIE at an irradiance of 20 mol m−2 s−1 using cool white florescent and incandescent light for 12 h. Humidity varied between 50 and 75%. Fully developed leaves were collected from mid-way up the stem in duplicate for foliar analysis as described (Roh et al., 2012).
Fig. 1. Coprosma, ‘Coppershine’ in 12.5 cm pot. Leaf from the main shoot as indicated with solid arrow and from the lateral shoots as indicated with dotted arrow is indicated. Leaves intact from the main shoot (Mi) and the lateral shoot (Li) and abscised from the main shoot (Ma) and the lateral shoot (La) are indicated.
For soluble carbohydrate analysis extracted with 80% ethanol, samples of mature leaves were collected in triplicate and analyzed as described previously (Lee and Roh, 2011). The number of leaves dried from the main shoot and lateral shoots were recorded on day 11 and on day 18 during evaluation under SIE. Leaves from the main shoot were larger than those from the lateral shoots, and absence of the abscised leaf scars from the node on the main shoots were examined to confirm the leaves dropped from the main shoot (Fig. 1). 2.2.3. Temperature, irradiance, and controlled release fertilizer treatment on growth and post-harvest physiology (Expt. 2) To investigate the effect of temperature, irradiance and fertilizer on plant growth, 5 cm long cuttings were collected from the stock plants as described above. We placed 15 rooted stem-tip cuttings planted into 12.5 cm pots per treatment were placed into two greenhouse sections maintained at 23 ◦ C/21 ◦ C and 21 ◦ C/15.5 ◦ C, day/night. Experimental treatments was carried out in a factorial design; 3 CRF (0, 2, or 4 g of CRF applied on the surface of the growing medium at planting) × 2 greenhouse temperatures × 3 supplementary light irradiance (no supplementary irradiance and at 218 and 316 mol m−2 s−1 from HID lamps as indicated above). Plants were fed weekly with 200 mg/L N from a 20N–8.6P–11.7K water soluble fertilizer. Plant height, plant width at one-half of the plant’s height, and the number of nodes were recorded 65 days after the initiation of treatments. From three median plants in height, leaves and shoots that were formed during treatments were collected for fresh and dry weight measurement following the sample drying method previously described. Six uniform plants representing the treatment
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Table 1 Growth of Coprosma, ‘Coppershine’ as influenced by controlled release fertilizer (CRF) and liquid fertilizer (LF) (Expt. 1). CRF
LF
FW (g)
DW (g)
Length (cm) of 5 longest shoots
0
200 400
36.2 69.3
0.75 1.98
1.8 4.4
2
200 400
64.7 61.9
1.73 2.45
3.3 4.8
4
200 400
68.9 67.7
2.62 3.17
4.8 4.8
Level of significancea CRF Linear Quadratic
*** *
** ns
*** ns
LF
**
**
***
*
***
*
11.8
0.28
0.87
CRF Linear × LF b
hsd at P < 0.05 or P < 0.01 a b
Weight and shoot length
Non-significant (ns) and significant difference at 5% (*), 1% (**), and 0.1% *(***), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.05 for the fresh weight and length and P < 0.01 for dry weight.
were selected and placed in a SIE 65 days after the initiation of treatments. The number of leaves abscissed in 7 days and the total number of leaves abscissed during 33 days of SIE was recorded from each plant. 2.3. Statistical analysis Data were subjected to analysis of variance and polynomial analysis was performed using general linear model. Linear and quadratic orthogonal contrasts were computed for the amount of CRF and the linear term of the interaction with other main variables is presented. Means were compared by Tukey’s honesty significant difference (hsd test) at P < 0.05 or P < 0.01. 3. Results 3.1. Effects of controlled fertilizer (CRF) and liquid fertilizer (LF) treatment on plant growth and post-production quality under a simulated interior environment (SIE) Fresh weight, dry weight and shoot length of the 5 longest shoots of plants which received 200 mg/L N LF was significantly less and shorter than the 64.7 g FW, 1.73 g DW, and 3.3 cm, respectively, which received 2 g CRF with 200 mg/L LF (Table 1). When plants received 200 mg/L N LF, the number of leaves abscissed by day 11 under SIE was the greatest; 18 leaves from the main shoot and 13 leaves from the lateral shoots (Table 2). The number was reduced to less than 6.8 and 4.0 when plants received 400 mg/L N LF. One or no leaves abscissed when plants received 2 g or 4 g CRF, regardless of LF concentration After 18 days, plants under SIE abscissed 24.7 leaves when provided with 200 mg/L LF. 3.2. Foliar macro- and micro-element levels, carbohydrate analyses, and assessment of leaf abscission Nitrogen (N) concentration (2.7%) in leaves formed in the middle of the stem (mid leaves) and receiving only 200 mg/L LF was the lowest, among all treatments (Table 3). The concentration of other elements; phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and manganese (Mn) also showed similar trends. The concentration of N and P was lower than the suggested normal range, K and Ca was within the suggested normal range, and Mg and Mn was higher than the suggested normal range (JR Peters Laboratory,
Allentown, PA, USA). The concentration of micro-elements; iron (Fe), zinc (Zn), and molybdenum (M) was within the suggested normal range; 60–200 ppm for Fe, 30–150 ppm for Zn, and 0.5–5.0 ppm for Mn. However, the concentration of boron (B), ranging from 15.5 mg kg−1 to 21.5 mg kg−1 , was lower than suggested normal ranges. The concentration of micro-elements of leaves that received only 200 mg/L N was generally lower than those that received CRF with LF treatments. The concentration of glucose was not affected by irradiance and CRF (Table 4). The concentration of fructose when plants received 4 g CRF and 400 mg/L N was the lowest when sampled on day 0 after SIE and again following 11 days at SIE. The decrease in fructose concentration following 11 days in an SIE regardless of CRF and LF concentration was evident. Although the concentration of glucose in leaves subjected to SIE that received 200 mg/L LF was 6.98 mg/g.fw, the concentration was not significantly affected by CRF, LF, and SIE. Sucrose concentration increased from 1.75 mg/g fw (400 mg/L LF at day 0 SIE) to 2.47 mg/g fw following 11 days at SIE. 3.3. Temperature, irradiance, and controlled release fertilizer (CRF) treatment on growth and post-harvest performance Plants were the tallest (29.8 cm) when they received supplementary irradiance of 316 mol m−2 s−1 and plant width and the fresh weight and dry weight also showed similar trends as those observed for the total plant height. (Data not presented.) In general, the plants were taller when grown at 21 ◦ C than those at 15.5 ◦ C and shorter when they received 4 g CRF, regardless of temperature and irradiance level. The number of nodes was less than 11.2 when plants were grown at 15.5 ◦ C under ND regardless of CRF treatment. When plants were grown at 21 ◦ C without receiving CRF, the number of leaves abscised on day 7 of SIE ranged from 1.3 leaves (ND + 218 mol m−2 s−1 ) to 1.7 leaves (ND + 316 mol m−2 s−1 ) was significantly less than the numbers abscissed, more than 2.5 when grown at 15.5 ◦ C (Table 5). When plants received 2 g or 4 g of CRF, the number of leaves abscised was significantly less than from plants that were grown without CRF. The number of leaves dropped after 7 days of SIE was less than 0.2 when plants were grown under the highest irradiance of 316 mol m−2 s−1 with 4 g CRF, a few leaves abscissed regardless of production temperature and CRF treatments. At 33 days of SIE, significantly fewer leaves abscissed if plants received 4 g CRF, regardless of production temperature and
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Table 2 The number of leaves dropped 11 and 18 days after simulated interior environment (SIE) treatment (Expt. 1). Treatmenta
Number of leaves dropped
Nutrition
Day 11b
Day 18 (total)
CRF
LF
Main shoot
Lateral shoots secondary
0
200 400
18.0 5.3
13.0 4.0
24.7 9.3
2
200 400
0.0 0.0
0.0 0.0
4.7 0.7
4
200 400
0.0 0.0
0.0 0.0
0.0 0.0
Level of significancec CRF Linear Quadratic
** **
** *
** **
LF
*
**
**
CRF Linear × LF
**
**
**
hsd, P < 0.01
1.28
2.36
2.84
a
Controlled release fertilizer (CRF) and liquid fertilizer (LF). Number of days at a ASIE. Linear (Lin) and quadratic (Quad) effect; non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01. b c
irradiance treatments. More leaves abscissed when plants were grown at high temperature (21 ◦ C) and under the highest irradiance (316 mol m−2 s−1 ) as compared to plants grown at low temperature (15.5 ◦ C) and mid level of irradiance (218 mol m−2 s−1 ).
4. Discussion Post-production quality of many foliage plants, especially F. benjamina has been investigated extensively and plants grown under sun and high fertilization required “acclimatization” to increase the quality and help leaf retention when they are moved to low irradiance interior environment. Without proper acclimatization, severe leaf drop will occur. However, the effect of irradiance, temperature, and nutrition on the growth of Coprosma as a greenhouse crop, and leaf abscission when placed in a SIE is not known.
4.1. Controlled fertilizer (CRF) and liquid fertilizer (LF) treatment on plant growth and post-production quality during a simulated interior environment (SIE) Reduced biomass as quantified by the fresh and dry weight when C. ‘Coppershine’ plants received only 200 mg/L N LF (0 g CRF + 200 mg/L LF) may be responsible for increased leaf loss when plants were placed in a SIE. Plants that received CRF treatments had increased fresh and dry weight and did not drop any leaves from the main shoot. This suggests that a constant supply of nutrients from CRF during greenhouse culture resulted in higher metabolic reserves when plants were placed in a SIE (Li et al., 2009) and thus, played an important role in leaf retention. The significant loss of leaves was also correlated with a low tissue N concentration in the leaves collected from mid-portion of the shoots after 11 days of SIE when leaf abscission became significant and at 15 days at
Table 3 The concentration of macro-and micro-elements of foliar analysis of C. ‘Coppershine’ collected from plants treated with controlled release fertilizer (CRF) and liquid fertilizer (LF) treatment during greenhouse forcing (Expt. 1). Treatmenta
Concentration
CRF
LF
N (%)
P (%)
K (%)
Ca (%)
Mg (%)
Mn (ppm)
0 2.0 4.0 0 2.0 4.0
200 200 200 400 400 400
2.7 3.4 4.0 4.0 5.0 4.5
2.75 3.05 3.80 3.65 3.60 3.75
2.15 2.25 2.40 2.50 2.70 2.65
0.90 1.45 1.20 1.40 1.45 1.55
2.20 2.20 2.45 2.60 3.10 3.35
260 314 292 309 311 275
ns *
** **
** **
ns **
** **
** **
* 0.51
** 0.48
ns 0.08
** 0.14
ns 0.37
ns 23.5
Level of significanceb CRF Linear LF CRF Linear × LF hsd at P < 0.05 or P < 0.01c a b c
Controlled release fertilizer (CRF) and liquid fertilizer (LF). Non-significant (ns) and significant difference at 5% (*)and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.05 for N or P < 0.01 and for all other elements.
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Table 4 The effect of irradiance, forcing temperature, and controlled release fertilizer (CRF) and liquid fertilizer (LF) during forcing and the duration of simulated interior environment (SIE) on soluble carbohydrates (Expt. 2). Treatment CRF
Soluble carbohydrate (mg/g fw) LF
Fructose
Glucose SIE
SIE
0
200 400 200 400 200 400
2 4 Level of significancea CRF Linear Quadratic LF Days at SIE CRF – linear × LF CRF – linear × SIE CRF – linear × LF SAE × LF CRF – linear × LF × SIE hsd at P < 0.01 a
Sucrose SIE
0
11
0
11
0
11
4.01 1.75 2.82 2.37 2.18 0.91
2.37 1.69 1.08 0.89 0.75 0.74
6.98 4.75 5.29 5.32 5.82 4.96
5.13 4.86 4.43 5.09 4.42 5.10
2.12 1.75 2.27 2.29 1.89 2.01
2.34 2.47 2.19 3.11 1.99 2.32
ns ns ns ns ns ns ns ns ns 2.24
** ** ** ** ** ns ** ns ns 0.94
** ns ns ** ns * ns ns ns 0.36
Non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01.
SIE, was lower than 2.7%, suggesting that tissue N concentration must be higher than 3.4% (2 g CRF + 200 mg/L N LF) to 4.0% (0 g CRF + 400 mg/L N LF) to prevent leaf loss. It is clear that nutrition should be steadily available to C. ‘Coppershine’ plants using 2–4 g CRF resulting in the increase of nitrogen tissue concentration higher than 4% to prevent leaf drop. This is the first report that leaf loss is reduced when leaf tissue
concentration of N is maintained at a high level following a steady supply of high fertilizer treatments. Numerous reports on Ficus reported that leaf loss was increased by high N fertilizer treatments (Johnson et al., 1979; Poole and Conover, 1982). The response to fertilizer in acclimatization may depend on the crop since fertilizer treatment using controlled release fertilizer during production of Dracaena marginata Lam. did not affect interior performance
Table 5 The number of leaves dropped in 7 days and the total number of leaves dropped during 33 days when plants were evaluated under a simulated interior environment (SIE) as influenced by irradiance, forcing temperature, and controlled release fertilizer (CRF) treatment. Treatment
Number of leaves dropped
Irradiance (mol m−2 s−1 )
Temp ( ◦ C)
CRF (g)
7 days under SIE
33 days under SIE
ND
15.5
0 2 4 0 2 4
2.7 1.2 0 1.6 1.1 0
15.0 9.3 4.3 17.8 13.2 7.3
0 2 4 0 2 4
2.5 1.8 0 1.2 1.4 0
17.3 14.7 4.7 15.8 13.5 7.5
0 2 4 0 2 4
2.7 2.1 0.2 1.7 1.0 0.2
17.7 17.2 6.7 16.0 16.2 9.3
ns ** ** * ns ** * 0.72
ns ** ** * ns ** * 4.83
21
ND + 218
15.5
21
ND + 316
15.5
21
Level of significancea Irradiance (Irrad.) – linear Temperature (Temp.) CRF Irrad. – linear × Temp. Irrad. – linear × CRF Temp. × CRF Irrad. – linear × Temp. × CRF hsd at P < 0.01 a
Non-significant (ns) and significant difference at 5% (*) and 1% (**), F-test. Mean comparisons were by Tukey’s honesty significant difference (hsd test) at P < 0.01.
J. Hong, J.K. Suh / Scientia Horticulturae 145 (2012) 46–51
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(Conover and Poole, 1975b). Reduced leaf drop in C. ‘Coppershine’ in plants grown with an increased fertilizer and high temperature is unique and different from findings in F. benjamina (Pennisi et al., 2005; Turner et al., 1987) and in Epipremnum aureum (Reyes et al., 1990). As expected, supplemented irradiance was not effective in reducing leaf drop.
supply of nutrition from the CRF is placed directly into a SIE without acclimatization. The data show that tissue nitrogen content of the mature leaves at the main shoot should be higher than 4% corresponding to 2 g of CRF treatment in a 12.5 pot. Whether the decrease in fructose is associated with leaf drops requires further investigation.
4.2. Foliar macro- and micro-elements and carbohydrate analyses and assessment of leaf loss
Acknowledgements
The tissue concentration of calcium (Ca) in the mid leaves may be associated with leaf loss, if physiological responses to Ca to inhibit ethylene induced abscission in bean petiole are similar (Poovaiah and Leopold, 1973). The tissue concentration of potassium (K), magnesium (Mg) (Poovaiah and Leopold, 1973), and phosphorus (P), and manganese (Mn) may not be associated with leaf loss and N, phosphorus (P), and K not with fruit abscission in Citrus sinensis [L.] Osbeck) (Ruiz et al., 2001). The tissue concentration of micro-elements did not differ significantly (data not presented) and may not be associated with leaf loss. The concentration of soluble glucose in tissue was not affected by irradiance and CRF (Table 4). The low concentration of fructose when plants received 4 g CRF and 400 mg/L N may be related to the reduced leaf drop. Is the reduced fructose associated with reduced leaf abscission in C. ‘Coppershine’? Application of exogenous fructose applied to plants prior to placing plants under a SIE and the abscisic acid (ABA) induced ethylene evolution on leaf abscission (Dunlap et al., 1991) should be investigated, although analysis of ethylene from large intact Coprosma plants may not be easy. If leaf drop is similar to fruitlet abscission, the sucrose and free reducing sugars should be reduced in C. ‘Coppershine’ as reported in the peel of the fruitlet (Citrus sinensis) (Ruiz et al., 2001). Hall and Lane (1952) reported that there is no relationship between soluble carbohydrates in the leaf blade and percentage of leaf defoliation in cotton responding to a defoliant chemical. However, in leaves of Arabidopsis thaliana (Izumi and Ishida, 2011), a remarkable accumulation of carbohydrates, glucose and fructose was observed in late senescent leaves at 10 days after bolting. 4.3. Temperature, irradiance, and controlled release fertilizer (CRF) treatment on growth and post-harvest physiology The interaction of temperature and CRF on the post-harvest quality as judged by leaf abscission was significant, while irradiance levels had no effect. The insignificant effect of irradiance on leaf abscission of C. ‘Coppershine’ is also unique as compared to the reports in F. benjamina as reviewed by Steinkamp et al. (1991). The irradiance level investigated in this study under greenhouse conditions may not be considered high, but is comparable to the intermediate irradiance (285 and 350 mol m−2 s−1 ) which increased the ornamental value of Pachira aquatica Aubl. (Li et al., 2009). Although leaf abscission is affected by irradiance and temperature during the greenhouse production phase, the most significant effect on leaf abscission is again correlated with the level of nutrition, since significantly fewer leaves abscissed when plants received 2–4 g CRF is observed, regardless of production temperature and irradiance treatments. 5. Conclusions This is the first report that leaf abscission is significantly reduced when C. ‘Coppershine’ grown in the greenhouse with a constant
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