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Response of potted plants of tropical origin to changes in the night temperature regime
ScientiaHorticulturae, 33 (1987) 299-305
299
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Response of Potted Plants of Tropical Origin to Changes in the Night Temperature Regime N. ZIESLIN, E. KHAYAT and SARAH YOGEV
The Hebrew University o/Jerusalem, Faculty o/Agriculture, P.O. Box 12, Rehovot 76100 (Israel) (Accepted for publication 5 June 1987)
ABSTRACT
Zieslin, N., Khayat, E. and Yogev, S., 1987. Response of potted plants of tropical origin to changes in the night temperature regime. Scientia Hortic., 33: 299-305. Growth of 1-year-old plants of Ficus benjamina cultivars 'Golden Princess' and 'Starlight', but not of young 'Starlight' plants, was inhibited when they were grown at a night temperature of 12°C in comparison with 18°C. Exposure of the plants to alternating night temperatures promoted growth of the young 'Starlight' plants, but did not affect the older plants of either cultivar of Ficus benjamina in comparison with plants grown at 18 ° C. Growth and branching (number of lateral shoots) of croton 'Petra' were promoted by exposure to an alternating night temperature regime relative to a constant temperaure of 18°C. The growth of 'Norma' was promoted under such conditions only when plants were decapitated. Alternating temperature caused an increase in the number of lateral shoots of Peperomia and Pilea, although the variegated Peperomia was not affected. The growth of Areca palms was not affected by alternating night temperatures in comparison with a higher constant temperature. Stem length, fresh weight and development of lateral shoots, but not new leaves of Di/fenbachia, were suppressed by exposure to an alternating temperature regime in comparison to a constant higher night temperature. Keywords: growth; night temperature; potted plants. Abbreviations: ATR = alternating temperature regime; HTR = high temperature regime; LTR = low temperature regime.
INTRODUCTION
Heating is a major factor affecting the economy of plant production in greenhouses. A number of different approaches may be used to reduce greenhouse heating requirements (Zieslin and Kohl, 1978). One such method employs "split-night temperature", which involves a partial lowering of the minimal temperature ( Gent et al., 1979). This method has been shown to be economically successful with some floriculture crops ( Carow and Zimmer, 1977; Shanks, 0304-4238/87/$03.50
© 1987 Elsevier Science Publishers B.V.
300 1979), while other crops showed a decline in growth and flower development following prolonged periods (6-7 h ) of exposure to sub-optimal temperatures (Hanan, 1979; Shanks and Osnos, 1980; Zieslin et al., 1986). However, the production of flowers and fruits of certain cultivars of roses and tomatoes was not significantly affected when they were exposed to short ( 2 h) but repetitive periods of sub-optimal temperature. Furthermore, some cultivars responded with a pronounced increase in the number of rose flowers or tomato fruits in comparison with a constantly maintained optimal night temperature regime (Khayat et al., 1985; Zieslin et al., 1986). Examination of the commercial application of an alternating night temperature regime in rose greenhouses showed that energy savings of 25-35% can be obtained by using this practice without any negative side-effects (Rosenzweig et al., 1986). In cultivation of greenhouse plants, the tropical foliage plants are among the most energy-consuming crops (Joiner, 1981) and the reduction in heating expenses is of great economic value in the production of tropical foliage potted plants. The possibility of saving energy in production of these plants by using alternating temperatures and examination of the effects of an alternating temperature regime on growth and development of some tropical foliage potted plants was the purpose of the present study. MATERIALSAND METHODS Plants were grown in three different compartments of a fibreglass-covered greenhouse. The following night temperature regimes were employed, one in each compartment, during two consecutive winter experimental periods: (1) high-temperature regime, minimum of 18 + 1 ° C continuously ( H T R ) ; ( 2 ) low-temperature regime, minimum of 12 + 1 ° C continuously ( LTR ) ; (3) alternating-temperature regime, 18 ° C for 2 h alternating repetitively with 12°C for 2 h (ATR). In order to diminish the possible interference of the differences in daylight intensity between the compartments with the night temperature, the temperature regimes were replicated by interchanging the temperature compartments during the second experimental period. Minimum and maximum day temperatures 18 and 30°C, respectively, were similarly maintained in all the compartments. The representative thermograms of the three night-temperature regimes are demonstrated elsewhere (Zieslin et al., 1987). Young plants of Ficus benjamina 'Starlight' were used during the first experimental period, while 1-year-old plants of 'Starlight' and 'Golden Princess' were examined during the second period. During the second experimental period, the tips of the main stems and of 10 lateral branches on each of the large plants of both cultivars were marked with white stain. The length and the fresh weight of new growth above the white mark were measured. The chlorophyll content of the
301
uppermost leaves ofF. benjamina 'Starlight' was determined as described elsewhere (Zieslin and Mor, 1981 ). Also tested in this study were two cultivars of Codiaeum variegatum var. picture (Syn. Croton), 'Petra' and 'Norma'. The plants of 'Petra' were grown in 15-cm pots and selected by uniformity of the lateral branch growth. Smaller plants of 'Norma' grown in 10-cm pots were divided into two groups; in each plant of the first group the tip was removed (pinching), while in the second group the tip was left intact. In both groups, the uppermost leaves were marked with a white stain. The increase in fresh weight above the marked leaves was measured in 'Norma' plants, while in 'Petra' plants the total fresh weight, stem length and the number of new leaves and lateral shoots above the mark were measured. Other species examined in this study were Peperomia caperata, Peperomia caperata variegata, Pilea cadierei, Diffenbachia ornamata and Areca palm ( Chrysalidocarpus lutescens). In the Areca palms the stem diameter was measured, and the stem cross-sectional area of all the stems in one container was calculated and combined. This parameter was previously found (I. Biran, Ornamental Horticulture, Rehovot, Israel, unpublished results, 1984) to be sufficient in non-destructive measurements of growth of Areca palms. All the plants were separated into two groups, 12 plants each, at two different locations of each compartment. The statistical analysis (Duncan's multiple range test, Snedecor, 1962 ) was performed separately for each group using one plant as a replicate. There were differences in growth of plants at different locations in the greenhouse. However, the plant response to the night-temperature treatments was similar in the two separate groups of plants at the two different locations. Therefore, the results are presented as an average of the two groups. RESULTS
The results presented in Table I show that, except for chlorophyll content, the growth of young plants of Ficus benjamina 'Starlight' over a 4-month period (14 January to 7 May 1985) was not significantly affected by the differences in the night-temperature regimes to which the plants were exposed. However, this was not the case with the older plants of F. benjamina (Table II). 'Golden Princess' was more sensitive than 'Starlight' to low temperature. The average stem elongation in 'Golden Princess' plants grown under LTR was 50% of that under HTR control treatment, while the corresponding difference in 'Starlight' was only 16%. An even greater difference in the response of the two Ficus cultivars to low and high night temperatures was observed with respect to lateral growth, expressed as the weight increment of 10 lateral shoots. Under LTR the lateral growth of 'Golden Princess' was 67% less than under HTR in comparison to a corresponding decrease of 35% in 'Starlight'.
302 TABLE 1 Effect of night-temperature regime on growth of young Ficus benjamina 'Starlight' plants during the period 14 J a n u a r y to 7 May 19851 Night temperature (°C)
Length of main stem (cm)
Fresh weight (g)
No. of lateral shoots
Chlorophyl ( ng g - 1 f.w. )
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
44.1 b 43.0 b 47.1 ~
89.6 89.5 85.6
21.3 20.3 21.1
1.05 ~ 0.78 ~' 0.88 ab
~In all tables, values in each column accompanied by different letters differ significantly at P= 0.05 (MRT). T A B L E II Effect of night-temperature regime on the growth of Ficus benjamina 'Starlight' and 'Golden Princess' during the period 28 November to 30 M a r c h 1986 Night temperature
Elongation of the main stem (cm)
Fresh weight increase of 10 lateral shoots (g)
'Starlight'
'Golden Princess'
'Starlight'
'Golden Princess'
14.3 t' 17.0 a 18.1"
10ft ) 20.0 a 22.2 a
22.2 b 34.2 a 35.3 ~
16.5 h 50.4 a 46.1 ~
(°c) 12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
The chlorophyll concentration in the leaves of the variegated 'Starlight' was higher following exposure to LTR than to HTR (Table I). Exposure of the Ficus benjamina plants to the alternating intervals of lower night temperature (ATR) did not have significant inhibitory effects on the elongation of the main stem or lateral shoot growth or chlorophyll content in comparison with plants grown at the HTR (Tables I and II). Exposure of'Petra' crotons to the LTR resulted in a marked decline in their fresh weight increase, development of new leaves and stem length in comparison with plants exposed to HTR. However, the formation of lateral shoots was promoted by LTR. Conversely, the exposure of 'Petra' plants to the ATR resulted in a pronounced increase in the first three parameters of growth in comparison to HTR, but the number of lateral shoots was reduced (Table III). A different response to ATR was shown by the unpinched croton plants of 'Norma' (Table IV); their fresh weight increment was reduced by almost 20% in comparison with plants exposed to HTR (53.4 vs. 67.0 g). However, exposure of decapitated (pinched) plants to ATR resulted in a relative increase in fresh weight increment (48.6 vs. 38.8 g in plants exposed to HTR). Growth of
303 T A B L E III Effect of night-temperature regime on growth of Codiaeum variegatum var. pictum 'Petra' during the period 14 J a n u a r y to 22 April 1985 Night temperature (°C)
Stem length (cm)
Fresh weight (g)
Number of new leaves
N u m b e r of lateral shoots
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
22.5 c 27.8 b 31.8 ~
218.0" 327.2 b 416.4 ~
12.6 c 17.8 b 20.8"
3.2 a 2.8 b 2.2 c
T A B L E IV Effect of night-temperature regime on the increase in fresh weight of decapitated (pinched) and non-decapitated plants of Codiaeum variegatum ' N o r m a ' during the period 28 November 1985 to 30 M a r c h 1986 Night temperature
Increase in fresh weight (g)
(°c)
Tip i n t a c t
Tip removed
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
13.3 h 67.0 a 53.4 a
8.0 c 38.8 ~ 48.6 ~
TABLE V Effect of night temperature regime on dry weight a n d b r a n c h i n g of Peperomia and Pilea cadierei plants during the period 14 J a n u a r y to 22 April 1985 Night temperature
Dry weight (g)
No. of lateral shoots per plant
(°c)
Peperomia aperata
Peperomia caperata variegata
Pilea cadierei
Peperomia caperata
Peperomia caperata variegata
Pilea cadierei
12 ( L T R ) 18 9 H T R ) 18/12 ( A T R )
5.0 a 4.7 a 5.7 a
3.5 ~ 4.1 b 5.18
7.6 b 7.1 b 10.2 ~
9.3 b 8.0 ~ 11.6 a
21.5 a 20.1 a 20.0"
16.1 b 12.6 c 19.6 ~
both pinched and unpinched plants, as expressed by the fresh weight increment, was inhibited by exposure to LTR. The effects of different night-temperature regimes on the growth of Peperomia and Pilea, as expressd by dry weight increments and by branching, are summarized in Table V. The dry weight increment of Peperomia caperata was
304 T A B L E VI Effect of n i g h t - t e m p e r a t u r e r e g i m e o n g r o w t h of Diffenbachia d u r i n g t h e p e r i o d 14 J a n u a r y to 22 April 1985 Night temperature ( °C )
Stem length (cm )
Fresh weight (g)
Number of n e w leaves
N u m b e r of lateral shoots
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
30.6 C 45.5 a 40.5 h
109.6" 285.5 a 177.0 h
2.3 ~ 3.2 ~ 3.1 ~
3.7 ¢ 8.3 a 5.3 h
T A B L E VII E f f e c t o f n i g h t - t e m p e r a t u r e r e g i m e o n g r o w t h o f Areca p a l m s d u r i n g t h e p e r i o d 1 F e b r u a r y to 15 M a y 1985 Night temperature ( °C )
S t e m crosssectional area ( c m 2)
Number of new leaves on m a i n stem
N u m b e r of new stems
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
21.7 t~ 28.6 a 30.8 a
1.6 ~ 2.1 a 2.0 ~
0.5 b 1.23 1.1 ~
not affected by the different regimes, although on exposure to ATR the average number of lateral shoots per branch was significantly increased relative to that for both LTR and HTR. In Peperomia variegata, on the other hand, branching was not affected on exposure to ATR, but the fresh weight increment increased by 25% relative to that on exposure to HTR. In Pilea plants, both the dry weight increment and branching were significantly higher in plants exposed to ATR than to either HTR or LTR. The growth of Diffenbachia plants was inhibited following their exposure to ATR. Their average stem length, fresh weight increment and number of lateral branches were lower by approximately 11, 35 and 36%, respectively, than in plants grown under HTR (Table VI). As shown in Table VII, growth of Areca palms was inhibited by exposure to LTR. However, when exposed to ATR the growth of these palms did not differ significantly from that of palms grown under HTR. DISCUSSION
The data presented in this study show that the effects of alternating night temperature are not restricted only to stimulation of flower development in roses and fruit set in tomatoes, but may also influence vegetative growth and
305 b r a n c h i n g . Differences in t h e r e s p o n s e of c e r t a i n p l a n t s to A T R were also s h o w n to be a f f e c t e d b y p l a n t age or stage of d e v e l o p m e n t ( T a b l e s I - I I I ) a n d b y hort i c u l t u r a l p r a c t i c e s ( T a b l e I V ) . D i f f e r e n t c u l t i v a r s of a p l a n t species m a y be s i m i l a r in s o m e r e s p o n s e s of g r o w t h b u t n o t others, as in Peperomias (Table V ). It is possible t h a t t h e effects of A T R on g r o w t h a n d d e v e l o p m e n t of v a r i o u s p l a n t species m a y be a t t r i b u t e d to a p o s i t i v e effect of t h e h i g h - t e m p e r a t u r e i n t e r v a l s on t h e t r a n s p o r t of a s s i m i l a t e s to t h e d i f f e r e n t p l a n t o r g a n s a n d m o bilization of a s s i m i l a t e s b y p l a n t s i n k s { K h a y a t a n d Zieslin, 1986) on t h e one h a n d , w i t h o u t t h e n e g a t i v e effects of t h e l o w - t e m p e r a t u r e i n t e r v a l s on the activity of t h e e n z y m e s i n v o l v e d in t h e m e t a b o l i s m of sucrose { K h a y a t a n d Zieslin, 1987) on the other. T h e use of a l t e r n a t i n g night t e m p e r a t u r e s in cultivation of g r e e n h o u s e p l a n t s a p p e a r s to offer a p r o m i s i n g a p p r o a c h to e n e r g y savings. H o w e v e r , t h e o p t i m a l d u r a t i o n of the high- a n d l o w - t e m p e r a t u r e intervals, as well as t h e m a g n i t u d e of t h e t e m p e r a t u r e difference in c u l t i v a t i o n of v a r i o u s p l a n t cultivars, will n e e d f u r t h e r i n v e s t i g a t i o n . R e s e a r c h into t h e physiological a n d b i o c h e m i c a l m e c h a n i s m s of p l a n t r e s p o n s e to a l t e r a t i o n s in t e m p e r a t u r e m a y also h a v e i m p o r t a n t a p p l i c a t i o n s in p l a n t b r e e d i n g a n d selection.
REFERENCES Carow, B. and Zimmer, K., 1977. Effects of change in temperature during long nights on flowering in chrysanthemum. Gartenbauwissenschaft, 42: 53-55. Gent, M.P.N., Thorn, J.H. and Aylor, D.E., 1979. Split-night temperature in a greenhouse: The effects on the physiology and growth of plants. Conn. Agric. Exp.Stn. Bull., 781: 1-15. Hanan, J.J., 1979. Observation of low temperature effects on roses. J. Am. Soc. Hortic. Sci., 104: 37-40. Joiner, J.N., 1981. Foliage Plant Production. Prentice-Hall, Englewood Cliffs, NJ. Khayat, E. and Zieslin, N., 1986. Effect of different night temperature regimes on the assimilation, transport and metabolism of carbon in rose plants. Physiol. Plant., 67: 608-613. Khayat, E. and Zieslin, N., 1987. Effect of night temperature on the activity of sucrose, phosphate synthase, acid invertase and sucrose synthase in source and sink tissues of Rosa hybrida cv. Golden Times. Plant Physiol., 84: 447-449. Khayat, E., Ravad, D. and Zieslin, N., 1985. The effects of various night-temperature regimes on the vegetative growth and fruit production of tomato plants. Scientia Hortic., 27: 9-13. Rosenzweig, N., Shayer, R. and Ben-Yehuda, Z., 1986. Alternating night temperature heating in a commercial rose greenhouse. Hassadeh, 67:2298-2299 (in Hebrew with English summary). Shanks, J.B., 1979. Growth of some greenhouse crops at several night temperature regimes. HortScience, 14: 472. Shanks, J.B. and Osnos, G.O., 1980. Growth of greenhouse roses at several split night temperature regimes. HortScience, 15: 387. Snedecor, G.W., 1962. Statistical Methods. Iowa State University Press, Ames, IA. Zieslin, N. and Kohl, H.C., 1978. Effects of low night temperatures on 'Princess Anne' mums. Flor. Rev., 161 (4180): 109-110. Zieslin, N. and Mor, Y., 1981. Plant management of greenhouse roses. Lateral bud removal. Scientia Hortic., 14: 387-393. Zieslin, N., Khayat, E. and Mor, Y., 1987. The response of rose plants to different night temperature regimes. J. Am. Soc. Hortic. Sci., 112: 86-89.
299
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Response of Potted Plants of Tropical Origin to Changes in the Night Temperature Regime N. ZIESLIN, E. KHAYAT and SARAH YOGEV
The Hebrew University o/Jerusalem, Faculty o/Agriculture, P.O. Box 12, Rehovot 76100 (Israel) (Accepted for publication 5 June 1987)
ABSTRACT
Zieslin, N., Khayat, E. and Yogev, S., 1987. Response of potted plants of tropical origin to changes in the night temperature regime. Scientia Hortic., 33: 299-305. Growth of 1-year-old plants of Ficus benjamina cultivars 'Golden Princess' and 'Starlight', but not of young 'Starlight' plants, was inhibited when they were grown at a night temperature of 12°C in comparison with 18°C. Exposure of the plants to alternating night temperatures promoted growth of the young 'Starlight' plants, but did not affect the older plants of either cultivar of Ficus benjamina in comparison with plants grown at 18 ° C. Growth and branching (number of lateral shoots) of croton 'Petra' were promoted by exposure to an alternating night temperature regime relative to a constant temperaure of 18°C. The growth of 'Norma' was promoted under such conditions only when plants were decapitated. Alternating temperature caused an increase in the number of lateral shoots of Peperomia and Pilea, although the variegated Peperomia was not affected. The growth of Areca palms was not affected by alternating night temperatures in comparison with a higher constant temperature. Stem length, fresh weight and development of lateral shoots, but not new leaves of Di/fenbachia, were suppressed by exposure to an alternating temperature regime in comparison to a constant higher night temperature. Keywords: growth; night temperature; potted plants. Abbreviations: ATR = alternating temperature regime; HTR = high temperature regime; LTR = low temperature regime.
INTRODUCTION
Heating is a major factor affecting the economy of plant production in greenhouses. A number of different approaches may be used to reduce greenhouse heating requirements (Zieslin and Kohl, 1978). One such method employs "split-night temperature", which involves a partial lowering of the minimal temperature ( Gent et al., 1979). This method has been shown to be economically successful with some floriculture crops ( Carow and Zimmer, 1977; Shanks, 0304-4238/87/$03.50
© 1987 Elsevier Science Publishers B.V.
300 1979), while other crops showed a decline in growth and flower development following prolonged periods (6-7 h ) of exposure to sub-optimal temperatures (Hanan, 1979; Shanks and Osnos, 1980; Zieslin et al., 1986). However, the production of flowers and fruits of certain cultivars of roses and tomatoes was not significantly affected when they were exposed to short ( 2 h) but repetitive periods of sub-optimal temperature. Furthermore, some cultivars responded with a pronounced increase in the number of rose flowers or tomato fruits in comparison with a constantly maintained optimal night temperature regime (Khayat et al., 1985; Zieslin et al., 1986). Examination of the commercial application of an alternating night temperature regime in rose greenhouses showed that energy savings of 25-35% can be obtained by using this practice without any negative side-effects (Rosenzweig et al., 1986). In cultivation of greenhouse plants, the tropical foliage plants are among the most energy-consuming crops (Joiner, 1981) and the reduction in heating expenses is of great economic value in the production of tropical foliage potted plants. The possibility of saving energy in production of these plants by using alternating temperatures and examination of the effects of an alternating temperature regime on growth and development of some tropical foliage potted plants was the purpose of the present study. MATERIALSAND METHODS Plants were grown in three different compartments of a fibreglass-covered greenhouse. The following night temperature regimes were employed, one in each compartment, during two consecutive winter experimental periods: (1) high-temperature regime, minimum of 18 + 1 ° C continuously ( H T R ) ; ( 2 ) low-temperature regime, minimum of 12 + 1 ° C continuously ( LTR ) ; (3) alternating-temperature regime, 18 ° C for 2 h alternating repetitively with 12°C for 2 h (ATR). In order to diminish the possible interference of the differences in daylight intensity between the compartments with the night temperature, the temperature regimes were replicated by interchanging the temperature compartments during the second experimental period. Minimum and maximum day temperatures 18 and 30°C, respectively, were similarly maintained in all the compartments. The representative thermograms of the three night-temperature regimes are demonstrated elsewhere (Zieslin et al., 1987). Young plants of Ficus benjamina 'Starlight' were used during the first experimental period, while 1-year-old plants of 'Starlight' and 'Golden Princess' were examined during the second period. During the second experimental period, the tips of the main stems and of 10 lateral branches on each of the large plants of both cultivars were marked with white stain. The length and the fresh weight of new growth above the white mark were measured. The chlorophyll content of the
301
uppermost leaves ofF. benjamina 'Starlight' was determined as described elsewhere (Zieslin and Mor, 1981 ). Also tested in this study were two cultivars of Codiaeum variegatum var. picture (Syn. Croton), 'Petra' and 'Norma'. The plants of 'Petra' were grown in 15-cm pots and selected by uniformity of the lateral branch growth. Smaller plants of 'Norma' grown in 10-cm pots were divided into two groups; in each plant of the first group the tip was removed (pinching), while in the second group the tip was left intact. In both groups, the uppermost leaves were marked with a white stain. The increase in fresh weight above the marked leaves was measured in 'Norma' plants, while in 'Petra' plants the total fresh weight, stem length and the number of new leaves and lateral shoots above the mark were measured. Other species examined in this study were Peperomia caperata, Peperomia caperata variegata, Pilea cadierei, Diffenbachia ornamata and Areca palm ( Chrysalidocarpus lutescens). In the Areca palms the stem diameter was measured, and the stem cross-sectional area of all the stems in one container was calculated and combined. This parameter was previously found (I. Biran, Ornamental Horticulture, Rehovot, Israel, unpublished results, 1984) to be sufficient in non-destructive measurements of growth of Areca palms. All the plants were separated into two groups, 12 plants each, at two different locations of each compartment. The statistical analysis (Duncan's multiple range test, Snedecor, 1962 ) was performed separately for each group using one plant as a replicate. There were differences in growth of plants at different locations in the greenhouse. However, the plant response to the night-temperature treatments was similar in the two separate groups of plants at the two different locations. Therefore, the results are presented as an average of the two groups. RESULTS
The results presented in Table I show that, except for chlorophyll content, the growth of young plants of Ficus benjamina 'Starlight' over a 4-month period (14 January to 7 May 1985) was not significantly affected by the differences in the night-temperature regimes to which the plants were exposed. However, this was not the case with the older plants of F. benjamina (Table II). 'Golden Princess' was more sensitive than 'Starlight' to low temperature. The average stem elongation in 'Golden Princess' plants grown under LTR was 50% of that under HTR control treatment, while the corresponding difference in 'Starlight' was only 16%. An even greater difference in the response of the two Ficus cultivars to low and high night temperatures was observed with respect to lateral growth, expressed as the weight increment of 10 lateral shoots. Under LTR the lateral growth of 'Golden Princess' was 67% less than under HTR in comparison to a corresponding decrease of 35% in 'Starlight'.
302 TABLE 1 Effect of night-temperature regime on growth of young Ficus benjamina 'Starlight' plants during the period 14 J a n u a r y to 7 May 19851 Night temperature (°C)
Length of main stem (cm)
Fresh weight (g)
No. of lateral shoots
Chlorophyl ( ng g - 1 f.w. )
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
44.1 b 43.0 b 47.1 ~
89.6 89.5 85.6
21.3 20.3 21.1
1.05 ~ 0.78 ~' 0.88 ab
~In all tables, values in each column accompanied by different letters differ significantly at P= 0.05 (MRT). T A B L E II Effect of night-temperature regime on the growth of Ficus benjamina 'Starlight' and 'Golden Princess' during the period 28 November to 30 M a r c h 1986 Night temperature
Elongation of the main stem (cm)
Fresh weight increase of 10 lateral shoots (g)
'Starlight'
'Golden Princess'
'Starlight'
'Golden Princess'
14.3 t' 17.0 a 18.1"
10ft ) 20.0 a 22.2 a
22.2 b 34.2 a 35.3 ~
16.5 h 50.4 a 46.1 ~
(°c) 12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
The chlorophyll concentration in the leaves of the variegated 'Starlight' was higher following exposure to LTR than to HTR (Table I). Exposure of the Ficus benjamina plants to the alternating intervals of lower night temperature (ATR) did not have significant inhibitory effects on the elongation of the main stem or lateral shoot growth or chlorophyll content in comparison with plants grown at the HTR (Tables I and II). Exposure of'Petra' crotons to the LTR resulted in a marked decline in their fresh weight increase, development of new leaves and stem length in comparison with plants exposed to HTR. However, the formation of lateral shoots was promoted by LTR. Conversely, the exposure of 'Petra' plants to the ATR resulted in a pronounced increase in the first three parameters of growth in comparison to HTR, but the number of lateral shoots was reduced (Table III). A different response to ATR was shown by the unpinched croton plants of 'Norma' (Table IV); their fresh weight increment was reduced by almost 20% in comparison with plants exposed to HTR (53.4 vs. 67.0 g). However, exposure of decapitated (pinched) plants to ATR resulted in a relative increase in fresh weight increment (48.6 vs. 38.8 g in plants exposed to HTR). Growth of
303 T A B L E III Effect of night-temperature regime on growth of Codiaeum variegatum var. pictum 'Petra' during the period 14 J a n u a r y to 22 April 1985 Night temperature (°C)
Stem length (cm)
Fresh weight (g)
Number of new leaves
N u m b e r of lateral shoots
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
22.5 c 27.8 b 31.8 ~
218.0" 327.2 b 416.4 ~
12.6 c 17.8 b 20.8"
3.2 a 2.8 b 2.2 c
T A B L E IV Effect of night-temperature regime on the increase in fresh weight of decapitated (pinched) and non-decapitated plants of Codiaeum variegatum ' N o r m a ' during the period 28 November 1985 to 30 M a r c h 1986 Night temperature
Increase in fresh weight (g)
(°c)
Tip i n t a c t
Tip removed
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
13.3 h 67.0 a 53.4 a
8.0 c 38.8 ~ 48.6 ~
TABLE V Effect of night temperature regime on dry weight a n d b r a n c h i n g of Peperomia and Pilea cadierei plants during the period 14 J a n u a r y to 22 April 1985 Night temperature
Dry weight (g)
No. of lateral shoots per plant
(°c)
Peperomia aperata
Peperomia caperata variegata
Pilea cadierei
Peperomia caperata
Peperomia caperata variegata
Pilea cadierei
12 ( L T R ) 18 9 H T R ) 18/12 ( A T R )
5.0 a 4.7 a 5.7 a
3.5 ~ 4.1 b 5.18
7.6 b 7.1 b 10.2 ~
9.3 b 8.0 ~ 11.6 a
21.5 a 20.1 a 20.0"
16.1 b 12.6 c 19.6 ~
both pinched and unpinched plants, as expressed by the fresh weight increment, was inhibited by exposure to LTR. The effects of different night-temperature regimes on the growth of Peperomia and Pilea, as expressd by dry weight increments and by branching, are summarized in Table V. The dry weight increment of Peperomia caperata was
304 T A B L E VI Effect of n i g h t - t e m p e r a t u r e r e g i m e o n g r o w t h of Diffenbachia d u r i n g t h e p e r i o d 14 J a n u a r y to 22 April 1985 Night temperature ( °C )
Stem length (cm )
Fresh weight (g)
Number of n e w leaves
N u m b e r of lateral shoots
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
30.6 C 45.5 a 40.5 h
109.6" 285.5 a 177.0 h
2.3 ~ 3.2 ~ 3.1 ~
3.7 ¢ 8.3 a 5.3 h
T A B L E VII E f f e c t o f n i g h t - t e m p e r a t u r e r e g i m e o n g r o w t h o f Areca p a l m s d u r i n g t h e p e r i o d 1 F e b r u a r y to 15 M a y 1985 Night temperature ( °C )
S t e m crosssectional area ( c m 2)
Number of new leaves on m a i n stem
N u m b e r of new stems
12 ( L T R ) 18 ( H T R ) 18/12 ( A T R )
21.7 t~ 28.6 a 30.8 a
1.6 ~ 2.1 a 2.0 ~
0.5 b 1.23 1.1 ~
not affected by the different regimes, although on exposure to ATR the average number of lateral shoots per branch was significantly increased relative to that for both LTR and HTR. In Peperomia variegata, on the other hand, branching was not affected on exposure to ATR, but the fresh weight increment increased by 25% relative to that on exposure to HTR. In Pilea plants, both the dry weight increment and branching were significantly higher in plants exposed to ATR than to either HTR or LTR. The growth of Diffenbachia plants was inhibited following their exposure to ATR. Their average stem length, fresh weight increment and number of lateral branches were lower by approximately 11, 35 and 36%, respectively, than in plants grown under HTR (Table VI). As shown in Table VII, growth of Areca palms was inhibited by exposure to LTR. However, when exposed to ATR the growth of these palms did not differ significantly from that of palms grown under HTR. DISCUSSION
The data presented in this study show that the effects of alternating night temperature are not restricted only to stimulation of flower development in roses and fruit set in tomatoes, but may also influence vegetative growth and
305 b r a n c h i n g . Differences in t h e r e s p o n s e of c e r t a i n p l a n t s to A T R were also s h o w n to be a f f e c t e d b y p l a n t age or stage of d e v e l o p m e n t ( T a b l e s I - I I I ) a n d b y hort i c u l t u r a l p r a c t i c e s ( T a b l e I V ) . D i f f e r e n t c u l t i v a r s of a p l a n t species m a y be s i m i l a r in s o m e r e s p o n s e s of g r o w t h b u t n o t others, as in Peperomias (Table V ). It is possible t h a t t h e effects of A T R on g r o w t h a n d d e v e l o p m e n t of v a r i o u s p l a n t species m a y be a t t r i b u t e d to a p o s i t i v e effect of t h e h i g h - t e m p e r a t u r e i n t e r v a l s on t h e t r a n s p o r t of a s s i m i l a t e s to t h e d i f f e r e n t p l a n t o r g a n s a n d m o bilization of a s s i m i l a t e s b y p l a n t s i n k s { K h a y a t a n d Zieslin, 1986) on t h e one h a n d , w i t h o u t t h e n e g a t i v e effects of t h e l o w - t e m p e r a t u r e i n t e r v a l s on the activity of t h e e n z y m e s i n v o l v e d in t h e m e t a b o l i s m of sucrose { K h a y a t a n d Zieslin, 1987) on the other. T h e use of a l t e r n a t i n g night t e m p e r a t u r e s in cultivation of g r e e n h o u s e p l a n t s a p p e a r s to offer a p r o m i s i n g a p p r o a c h to e n e r g y savings. H o w e v e r , t h e o p t i m a l d u r a t i o n of the high- a n d l o w - t e m p e r a t u r e intervals, as well as t h e m a g n i t u d e of t h e t e m p e r a t u r e difference in c u l t i v a t i o n of v a r i o u s p l a n t cultivars, will n e e d f u r t h e r i n v e s t i g a t i o n . R e s e a r c h into t h e physiological a n d b i o c h e m i c a l m e c h a n i s m s of p l a n t r e s p o n s e to a l t e r a t i o n s in t e m p e r a t u r e m a y also h a v e i m p o r t a n t a p p l i c a t i o n s in p l a n t b r e e d i n g a n d selection.
REFERENCES Carow, B. and Zimmer, K., 1977. Effects of change in temperature during long nights on flowering in chrysanthemum. Gartenbauwissenschaft, 42: 53-55. Gent, M.P.N., Thorn, J.H. and Aylor, D.E., 1979. Split-night temperature in a greenhouse: The effects on the physiology and growth of plants. Conn. Agric. Exp.Stn. Bull., 781: 1-15. Hanan, J.J., 1979. Observation of low temperature effects on roses. J. Am. Soc. Hortic. Sci., 104: 37-40. Joiner, J.N., 1981. Foliage Plant Production. Prentice-Hall, Englewood Cliffs, NJ. Khayat, E. and Zieslin, N., 1986. Effect of different night temperature regimes on the assimilation, transport and metabolism of carbon in rose plants. Physiol. Plant., 67: 608-613. Khayat, E. and Zieslin, N., 1987. Effect of night temperature on the activity of sucrose, phosphate synthase, acid invertase and sucrose synthase in source and sink tissues of Rosa hybrida cv. Golden Times. Plant Physiol., 84: 447-449. Khayat, E., Ravad, D. and Zieslin, N., 1985. The effects of various night-temperature regimes on the vegetative growth and fruit production of tomato plants. Scientia Hortic., 27: 9-13. Rosenzweig, N., Shayer, R. and Ben-Yehuda, Z., 1986. Alternating night temperature heating in a commercial rose greenhouse. Hassadeh, 67:2298-2299 (in Hebrew with English summary). Shanks, J.B., 1979. Growth of some greenhouse crops at several night temperature regimes. HortScience, 14: 472. Shanks, J.B. and Osnos, G.O., 1980. Growth of greenhouse roses at several split night temperature regimes. HortScience, 15: 387. Snedecor, G.W., 1962. Statistical Methods. Iowa State University Press, Ames, IA. Zieslin, N. and Kohl, H.C., 1978. Effects of low night temperatures on 'Princess Anne' mums. Flor. Rev., 161 (4180): 109-110. Zieslin, N. and Mor, Y., 1981. Plant management of greenhouse roses. Lateral bud removal. Scientia Hortic., 14: 387-393. Zieslin, N., Khayat, E. and Mor, Y., 1987. The response of rose plants to different night temperature regimes. J. Am. Soc. Hortic. Sci., 112: 86-89.