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Growth rate of cotton bolls and their components
Field Crops Research, 2 (1979) 169--175 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
169
GROWTH RATE OF COTTON BOLLS AND THEIR COMPONENTS
A. MARANI Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot (Israel)
(Accepted 21 May 1979)
ABSTRACT Marani, A.~ 1979. Growth rate of cotton bolls and their components. Field Crops Res., 2: 169--175. The growth rate of cotton, Gossypiurn hirsutum L., bolls was investigated at three locations in the Coastal Plain of Israel. Random samples of bolls that had been tagged at anthesis were periodically taken. Burs and seed-cotton were weighed separately, after being dried, for each boll. The weight of the two heaviest bolls in each sample was taken as 'potential weight', and a temperature-dependent time-scale was used. It was found that the potential growth of whole cotton bolls may be modelled by using the following assumptions: (a) seed-cotton dry-weight follows a sigmoid function; (b) bur dry weight grows linearly during 21 days, with no further growth later on; (c) there is a maximum rate of boll growth with priority to seed-cotton, causing a decrease in bur dry weight during peak seed-cotton growth. Parameters for the cultivar Acala SJ-1 were calculated by fitting the functions to the observed data. Average boll weight was only 0.65-0.85 of the potential weight, probably because of stresses affecting whole plants or sites of individual bolls.
INTRODUCTION T h e r a t e o f d e v e l o p m e n t o f c o t t o n bolls has b e e n investigated b y several a u t h o r s . Mogilner et al. ( 1 9 6 5 ) f o u n d t h a t t h e m a x i m u m w e i g h t o f d r y - m a t t e r o f s e e d - c o t t o n was r e a c h e d 40 d a y s a f t e r anthesis, whereas t h a t o f t h e b u r s was r e a c h e d 20 d a y s a f t e r anthesis a n d t h e n d e c r e a s e d s o m e w h a t until m a t u r i t y . B e n e d i c t et al. ( 1 9 7 3 ) f o u n d t h a t f i b e r g r o w t h in d r y w e i g h t r e s e m b l e d a sigm o l d curve. T h e m a x i m u m r a t e o f increase o c c u r r e d at 2 5 - - 3 0 d a y s a f t e r anthesis, a n d f i b e r d r y w e i g h t was m a x i m a l 4 0 - 4 5 d a y s a f t e r anthesis. S c h u b e r t et al. ( 1 9 7 3 ) investigated f i b e r d r y w e i g h t p e r seed in d e v e l o p i n g c o t t o n bolls a n d f i t t e d t h e logistic g r o w t h curve t o t h e i r d a t a ; t h e m a x i m u m r a t e o f d r y w e i g h t increase o c c u r r e d 2 7 - - 3 0 d a y s a f t e r anthesis. Mutsaers ( 1 9 7 6 a ) r e v i e w e d t h e l i t e r a t u r e o n c o t t o n boll g r o w t h a n d cons t r u c t e d " a n idealized p a t t e r n o f g r o w t h o f bolls a n d boll c o m p o n e n t s " . He c o n c l u d e d t h a t d u r i n g initial g r o w t h a l m o s t all w e i g h t increase is a p p a r e n t l y invested in t h e bur, t h e n b u r w e i g h t f l a t t e n s o f f a n d during t h e final g r o w t h
170
period it decreases. The postulated decrease in bur weight coincides with a strong decrease in carbohydrate content of the burs. Leffler (1976) found that dry weight of the bur increased rapidly and reached final weight by the end of the third week of development, whereas both the seed and the fiber accumulated dry matter for about 6 weeks. Several authors have investigated the effect of temperature on boll maturation periods (BMP). Gipson and Ray (1970) referred to night and day temperatures, Morris (1964) to average maximum temperatures, Yfoulis and Fasoulas (1973) to mean daily temperatures. They all found a negative correlation between BMP and temperature. Mutsaers (1976b) fitted an exponential equation to the effect of temperature on the rate of boll development and found a Q~0 value of 2.46-2.56 for the range of 15--30 ° C. Knowledge of the growth rate of individual cotton bolls is necessary for developing cotton simulation models. Several teams of investigators have attempted to construct such models. Thornley and Hesketh (1972) fitted a third degree polynomial of boll age to the logarithm of boll dry weight. Stapleton et al. (1973), in one of the first cotton plant models, assumed that each fruitform has a daily requirement of photosynthate which increases exponentially with age during its first 35 days (until 2 weeks after anthesis) and after that remains constant (at 0.227 g/day) until boll maturation. McKinion et al. (1975) assumed in their SIMCOT model an exponential growth rate during the first week after anthesis, a constant rate (0.225 g/day) during the next 3 weeks, and a gradually decreasing rate afterwards. Gutierrez et al. {1975) assumed in their model that bolls begin their exponential growth phase when the associated leaf has reached its maximum size, i.e., 1--2 weeks after anthesis. Wallach (1978) assumed in his simplified model a constant growth rate (0.24 g per physiological day) for a period of 41 physiological days beginning at 5 days after anthesis. These models did not consider the inherently different growth patterns of the components of the boll. It may be misleading to describe the growth pattern of any plant organ, which consists of several distinct entities, by a single equation. The growth pattern of each component should be considered individually, and possible interactions between the components should not be ignored. Cotton bolls consist of burs, seeds, and lint. The growth pattern of the seeds and the lint is very similar (Mutsaers, 1976a), and they may therefore be considered together as 'seed-cotton'. The purpose of the present investigation was to study the growth pattern of cotton bolls, which are treated as consisting of two parts, seed-cotton and burs. MATERIALS AND METHODS
Flowers of upland cotton (Gossypium hirsutum L., cultivar Acala SJ-1) were tagged at anthesis in three locations in the Coastal Plain of Israel. In Yavne (latitude 31 ° 49' N) 200 flowers were tagged on June 30 in each of three fields. These were planted on March 28, April 4 and April 18, and began to flower on June 20, 24 and 28, respectively. Samples of 10 random tagged bolls
171
were taken from each field on five dates. The field in Galon (latitude 31 ° 38' N) was planted on April 9 in skip-rows (two rows alternating with t w o missing rows) and began to flower on June 20. Two-hundred flowers were tagged here on each of t w o dates: June 24 and July 4. Samples of 10 random tagged bolls were taken from each tagging date at 10--14-day intervals. The field in EinShemer (latitude 32 ° 27' N) was planted on March 28 and began to flower on June 12. Five-hundred flowers were tagged here on July 7, and samples of 20 random tagged bolls were taken at 6--8-day intervals. All the fields were on a fertile alluvial clay-loam, and recommended cultural practices and insecticidal treatments were applied. Rows were spaced 96.5 cm (with the exception of Galon), and there were, on average, 11, 9 and 13 plants per 1 m of row at Yavne, Galon and Ein-Shemer, respectively. Three irrigations were applied in Yavne and Ein-Shemer, and only one irrigation in Galon. Yields of seed-cotton were 5700, 5400 and 4700 kg/ha in the three fields of Yavne, and 2200 and 5300 kg/ha in Galon and Ein-Shemer, respectively. The dates of sampling from each field are given in Table I. Daily maximum and minimum temperatures were recorded at each location. A temperature-dependent 'physiological age', from anthesis to each sampling date, was calculated as in the SIMCOT c o t t o n model (McKinion et al., 1975). (1) When maximum temperatures were above 30 ° C, they were taken as 30 ° C. (2) Average day and night temperatures (TD and TN) were calculated from maximum and minimum temperatures (TMAX and TMIN) by using the empirical factors 0.77 and 0.19, as follows: TD = TMIN + 0 . 7 7 . ( T M A X - T M I N ) TN = TMIN + 0 . 1 9 - ( T M A X - T M I N ) (3) Day-degrees above the threshold of 12 ° C were separately calculated for day and night and weighted by day and night lengths. (4) The sum of day-degrees was divided by 14, thus making a 'physiological day' equivalent to one day with a constant temperature of 26 ° C. The physiological age at each sampling date is also given in Table I. The sampled bolls were dried in a ventilated oven at 80 ° C for 1 week, and each boll was individually weighed. Seed cotton and burs were weighed separately in Galon and Yavne, whereas data for whole bolls only were available for EinShemer. RESULTS AND DISCUSSION
A very high variation in the weight of dry matter was found among individual bolls in each sample. Obviously, most of these bolls did n o t develop to their full potential weight. Therefore, the two heaviest bolls in each sample were chosen to represent, as nearly as possible, the potential development of boll weight. In order to remove the effect of temperature, the time-scale was expressed
172 TABLE I Dates of sampling, and 'physiological age' (PA) from anthesis at each sampling date Location
Tagging date
Sampling date and physiological age
Yavne
June 30
Date: PA:
July 11 9.8
July 23 19.7
Aug. 22 48.7
Aug. 31 56.4
Sept. lO 65.4
Galon
June 24
Date: PA:
July 4 9.0
July 18 21.7
July 28 30.9
Aug. 41.0
8
Aug. 18 50.2
Galon
July 4
Date: PA:
July 18 12.7
July 28 21.9
Aug. 8 32.0
Aug. 18 41.2
Aug. 29 50.9
Ein-Shemer
July 7
Date: PA:
July 19 10.1
July 26 16.1
Aug. 2 22.2
Aug. 10 29.1
Aug. 16 34.8
Date: PA:
Sept. 5 51.1
Sept.12 56.9
Sept.19 62.2
Sept. 27 67.6
as 'physiological age' from anthesis (see Table I). This assumes that the effect of temperature on growth-rate is linear in the range of 12--30 ° C. Mutsaers (1976b) found an exponential effect of temperature on the rate of boll growth, but in the range of temperatures encountered at the three locations during boll development (17--22 ° C minimum and 28--32 ° C maximum) the deviation of the linear function from the exponential one is negligible. The use of a temperature-dependent time-scale makes it possible to find a boll growth curve c o m m o n to all the locations and tagging dates used in this study. Data for the 'potential' weight of dry-matter of seed-cotton (from the two heaviest bolls in each sample) are given in Fig.1. The sigmoid function could be fitted to these data. The weight of seed cotton per boll in g, Ws, at physiological age T, and the growth rate d W s / d T are as follows: Ws = A/(1 + B . E X P ( - C . T ) )
(1)
d W s / d T = C. Ws" ( 1 - Ws/A)
(2)
By using the least-squares method to fit this function to the data, the following estimates of the parameters were found: A = 9.455, B = 54.31, C = 0.1467 The theoretical growth curve, using Eqn. (1) with these parameters is given in Fig.1. Data for bur weight of the two heaviest bolls in each sample, given in Fig.2, indicate a linear increase in bur weight until the age of 21 physiological days. The growth rate was 0.145 g/physiological day during this period. After that, there was a slight decrease in bur weight, and it remained constant later on. The linear phase of bur growth coincided with the rapid increase in boll volume, and ended when the boll reached its final size, as was also noted by Benedict et al. (1973) and Leffler (1976). The subsequent decrease in bur weight was
173
8~
Z~ GALON
~
"
rn
T
1
T--T
1 W
1"
|
o
[] 2 [] YAVNE & GALON
0
10
L
l
I
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
70
c) o',q
I
10
I
I
I I i
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
Fig. 1. Potential weight of seed-cotton, weight of dry matter, g/boll: calculated growth curve and validation points. Fig.2. Potential weight of burs, weight of dry matter, g/boll: calculated growth curve and validation points. also observed by Mogilner et al. (1965) and Mutsaers (1976a). It was probably caused by translocation of carbohydrates from the burs to the rapidly growing seeds and fibers (Mutsaers, 1976a). This can be included in the model of boll growth b y assuming a maximum rate of boll growth of 0.28 g per physiological day, limited by carbohydrate supply to the whole boll. This is an empirical parameter that gave the best fit to our data. When the potential growth rate of the seed c o t t o n exceeds this maximum, a decrease in bur weight occurs. The growth rate of the dry weight of the burs (WB) may therefore be expressed as follows: t MIN (0.145; 0 . 2 8 - d W s / d T )
1 <~ T <~ 21
(3)
dWB/dT =
MIN (0
; 0.28-dWs/dT)
21 < T
The theoretical growth curve of the burs, using these equations, is given in Fig.2. At the physiological age of 22--33 days growth rate of seed cotton was higher than 0.28, and consequently the growth rate of burs was negative during this period. A fairly good fit to the observed data was obtained (Fig.2) and the growth curve resembled that postulated by Mutsaers (1976a). The potential growth curve of whole bolls (seed-cotton plus burs) may be calculated b y using the above assumptions. This curve and the actual data for the three locations are given in Fig. 3. The actual ratio of burs in the whole bolls was calculated for the whole samples (average bolls) and also for the t w o largest bolls; these did n o t differ significantly. The results for average bolls are given in Fig.4. The theoretical ratio of burs in the whole bolls, calculated by
70
174
12
r [] YAVNE A GALON
7
T
T
F
r
A 0.8~
O EIN-SHEMER
~
_
~
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~
~
--
/
.C.
I i i
A
U YAVNE
,~-. ^ / \~
0.6!
Z~ GALON
\
~o.~ cz
0.2
L. . . . .~ . I • __ 20 30 40 50 BOLL AGE IN PHYS. DAYS
I
0
10
l
I
60
70
R
~
10
_
I
I
I
I
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
70
Fig. 3. Potential weight of whole bolls, weight of dry matter, g/bolh calculated growth curve and validation points. Fig.4. The ratio of bur weight to whole boll weight, calculated and real data.
using the above equations, also given in Fig.4, was very close to the actual ratio. The average boll weight in each sample was in the range of 65--85% of the calculated potential boll weight (Fig.5). Most of the bolls probably did not attain their potential weight because of moisture-stress, carbohydrate-stress, nitrogen-stress, or other stresses that may affect the whole plant or sites of individual bolls. The average boll weight at Ein-Shemer was lower than at the other two locations, probably because of the large number of bolls carried by the plants. There were 87 bolls/m 2 at maturity at Ein-Shemer, as compared to 72 and 32 at Yavne and Galon, respectively. 09--
[
T
T
]
[] YAVNE A GALON O EIN-SHEMER O A
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o w0,7
~
" I
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O
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I__ I _ I _ I ] 20 30 40 50 60 BOLL AGE IN PHYS. DAYS
_% ?O
Fig. 5. The ratio of average weight of whole bolls to their calculated potential weight.
175
The general principles of modelling boll growth, as outlined above, may probably be applied to any cultivar of upland cotton. However, the actual values of the parameters (A, B, C in Eqns. (1) and (2); 0.145, 0.28, 21 in Eqn. (3)) are true only for 'Acala SJ-l' and closely related cultivars, and should be empirically adjusted for any other cultivar. The temperatur~related time-scale used gave good results in the mild temperature conditions of our observation fields. However, it may presumably have to be somewhat modified for conditions of extremely high or low temperatures. ACKNOWLEDGEMENT
The assistance of Mr. E. Kletter and Mr. A. Goren, and the help of the cotton growers at the three farms, are gratefully acknowledged. This research was financed by the Cotton Production and Marketing Board of Israel.
REFERENCES Benedict, C.R., Smith, R.H. and Kohel, R.J., 1973. Incorporation of '4C-photosynthate into developing c o t t o n bolls, Gossypium hirsutum L. Crop Sci., 13: 88--91. Gipson, J.R. and Ray, L.L., 1970. Temperature-variety interrelationships in cotton. Cott. Grow. Rev., 47: 257--271. Gutierrez, A.P., Falcon, L.A., Loew, W., Leipzig, P.A. and Van Den Bosch, R., 1975. An analysis of cotton production in California: a model for Acala c o t t o n and the effects of defoliators on its yields. Environ. Entomol., 4: 125--136. Leffler, H.R., 1976. Development of c o t t o n fruit. I. Accumulation and distribution of dry matter. Agron. J., 68: 855--857. McKinion, J.IVL, Baker, D.N., Hesketh, J.D. and Jones, J.W., 1975. SIMCOT II: a simulation of c o t t o n growth and yield. ARS-S-52, USDA, pp. 27--82. Mogilner, I., Turn, B. and PUatti, O.F., 1965. La distribucion de nitrogeno, fosforo y calcion en carpellos y semillas durante la formacion del fruto del algodonero. Phyton, 22: 127-130. Morris, D.A., 1964. Variation in the boll maturation periods of cotton. Cott. Grow. Rev., 41: 114--123. Mutsaers, H.J.W., 1976a. Growth and assimilate conversion of cotton bolls (Gossypium hirsutum L). 1. Growth of fruit and substrate demand. Ann. Bot., 40: 301--315. Mutsaers, H.J.W., 1976b. Growth and assimilate conversion of cotton bolls (Gossypium hirsutum L). 2. Influence of temperature on boll maturation period and assimilate conversion. Ann. Bot., 40: 317--324. Schubert, A M . , Benedict, C.R., Berlin, J.D. and Kohel, R.J., 1973. Cotton fiber development - - kinetics of cell elongation and secondary wall thickening. Crop Sci., 13: 704--709. Stapleton, I-LN., Buxton, D.R., Watson, F.L., Nolting, D.J. and Baker, D.N., 1973. Cotton: a Computer Simulation of Cotton Growth. Agric. Exp. Stn, Univ. Arizona, Tech. Bull., 206, 124 pp. Thornley, J.H.M. and Hesketh, J.D., 1972. Growth and respiration in cotton bolls. J. Appl. Ecol., 9: 315--317. Wallach, D., 1978. A simple model of cotton yield development. Field Crops Res., 1 : 2 6 9 - - 2 8 1 Yfoulis, A. and Fasoulas, A., 1973. Interaction of genotype and temperature on cotton boll period and their implication in breeding. Exp. Agric., 9: 193--201.
169
GROWTH RATE OF COTTON BOLLS AND THEIR COMPONENTS
A. MARANI Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot (Israel)
(Accepted 21 May 1979)
ABSTRACT Marani, A.~ 1979. Growth rate of cotton bolls and their components. Field Crops Res., 2: 169--175. The growth rate of cotton, Gossypiurn hirsutum L., bolls was investigated at three locations in the Coastal Plain of Israel. Random samples of bolls that had been tagged at anthesis were periodically taken. Burs and seed-cotton were weighed separately, after being dried, for each boll. The weight of the two heaviest bolls in each sample was taken as 'potential weight', and a temperature-dependent time-scale was used. It was found that the potential growth of whole cotton bolls may be modelled by using the following assumptions: (a) seed-cotton dry-weight follows a sigmoid function; (b) bur dry weight grows linearly during 21 days, with no further growth later on; (c) there is a maximum rate of boll growth with priority to seed-cotton, causing a decrease in bur dry weight during peak seed-cotton growth. Parameters for the cultivar Acala SJ-1 were calculated by fitting the functions to the observed data. Average boll weight was only 0.65-0.85 of the potential weight, probably because of stresses affecting whole plants or sites of individual bolls.
INTRODUCTION T h e r a t e o f d e v e l o p m e n t o f c o t t o n bolls has b e e n investigated b y several a u t h o r s . Mogilner et al. ( 1 9 6 5 ) f o u n d t h a t t h e m a x i m u m w e i g h t o f d r y - m a t t e r o f s e e d - c o t t o n was r e a c h e d 40 d a y s a f t e r anthesis, whereas t h a t o f t h e b u r s was r e a c h e d 20 d a y s a f t e r anthesis a n d t h e n d e c r e a s e d s o m e w h a t until m a t u r i t y . B e n e d i c t et al. ( 1 9 7 3 ) f o u n d t h a t f i b e r g r o w t h in d r y w e i g h t r e s e m b l e d a sigm o l d curve. T h e m a x i m u m r a t e o f increase o c c u r r e d at 2 5 - - 3 0 d a y s a f t e r anthesis, a n d f i b e r d r y w e i g h t was m a x i m a l 4 0 - 4 5 d a y s a f t e r anthesis. S c h u b e r t et al. ( 1 9 7 3 ) investigated f i b e r d r y w e i g h t p e r seed in d e v e l o p i n g c o t t o n bolls a n d f i t t e d t h e logistic g r o w t h curve t o t h e i r d a t a ; t h e m a x i m u m r a t e o f d r y w e i g h t increase o c c u r r e d 2 7 - - 3 0 d a y s a f t e r anthesis. Mutsaers ( 1 9 7 6 a ) r e v i e w e d t h e l i t e r a t u r e o n c o t t o n boll g r o w t h a n d cons t r u c t e d " a n idealized p a t t e r n o f g r o w t h o f bolls a n d boll c o m p o n e n t s " . He c o n c l u d e d t h a t d u r i n g initial g r o w t h a l m o s t all w e i g h t increase is a p p a r e n t l y invested in t h e bur, t h e n b u r w e i g h t f l a t t e n s o f f a n d during t h e final g r o w t h
170
period it decreases. The postulated decrease in bur weight coincides with a strong decrease in carbohydrate content of the burs. Leffler (1976) found that dry weight of the bur increased rapidly and reached final weight by the end of the third week of development, whereas both the seed and the fiber accumulated dry matter for about 6 weeks. Several authors have investigated the effect of temperature on boll maturation periods (BMP). Gipson and Ray (1970) referred to night and day temperatures, Morris (1964) to average maximum temperatures, Yfoulis and Fasoulas (1973) to mean daily temperatures. They all found a negative correlation between BMP and temperature. Mutsaers (1976b) fitted an exponential equation to the effect of temperature on the rate of boll development and found a Q~0 value of 2.46-2.56 for the range of 15--30 ° C. Knowledge of the growth rate of individual cotton bolls is necessary for developing cotton simulation models. Several teams of investigators have attempted to construct such models. Thornley and Hesketh (1972) fitted a third degree polynomial of boll age to the logarithm of boll dry weight. Stapleton et al. (1973), in one of the first cotton plant models, assumed that each fruitform has a daily requirement of photosynthate which increases exponentially with age during its first 35 days (until 2 weeks after anthesis) and after that remains constant (at 0.227 g/day) until boll maturation. McKinion et al. (1975) assumed in their SIMCOT model an exponential growth rate during the first week after anthesis, a constant rate (0.225 g/day) during the next 3 weeks, and a gradually decreasing rate afterwards. Gutierrez et al. {1975) assumed in their model that bolls begin their exponential growth phase when the associated leaf has reached its maximum size, i.e., 1--2 weeks after anthesis. Wallach (1978) assumed in his simplified model a constant growth rate (0.24 g per physiological day) for a period of 41 physiological days beginning at 5 days after anthesis. These models did not consider the inherently different growth patterns of the components of the boll. It may be misleading to describe the growth pattern of any plant organ, which consists of several distinct entities, by a single equation. The growth pattern of each component should be considered individually, and possible interactions between the components should not be ignored. Cotton bolls consist of burs, seeds, and lint. The growth pattern of the seeds and the lint is very similar (Mutsaers, 1976a), and they may therefore be considered together as 'seed-cotton'. The purpose of the present investigation was to study the growth pattern of cotton bolls, which are treated as consisting of two parts, seed-cotton and burs. MATERIALS AND METHODS
Flowers of upland cotton (Gossypium hirsutum L., cultivar Acala SJ-1) were tagged at anthesis in three locations in the Coastal Plain of Israel. In Yavne (latitude 31 ° 49' N) 200 flowers were tagged on June 30 in each of three fields. These were planted on March 28, April 4 and April 18, and began to flower on June 20, 24 and 28, respectively. Samples of 10 random tagged bolls
171
were taken from each field on five dates. The field in Galon (latitude 31 ° 38' N) was planted on April 9 in skip-rows (two rows alternating with t w o missing rows) and began to flower on June 20. Two-hundred flowers were tagged here on each of t w o dates: June 24 and July 4. Samples of 10 random tagged bolls were taken from each tagging date at 10--14-day intervals. The field in EinShemer (latitude 32 ° 27' N) was planted on March 28 and began to flower on June 12. Five-hundred flowers were tagged here on July 7, and samples of 20 random tagged bolls were taken at 6--8-day intervals. All the fields were on a fertile alluvial clay-loam, and recommended cultural practices and insecticidal treatments were applied. Rows were spaced 96.5 cm (with the exception of Galon), and there were, on average, 11, 9 and 13 plants per 1 m of row at Yavne, Galon and Ein-Shemer, respectively. Three irrigations were applied in Yavne and Ein-Shemer, and only one irrigation in Galon. Yields of seed-cotton were 5700, 5400 and 4700 kg/ha in the three fields of Yavne, and 2200 and 5300 kg/ha in Galon and Ein-Shemer, respectively. The dates of sampling from each field are given in Table I. Daily maximum and minimum temperatures were recorded at each location. A temperature-dependent 'physiological age', from anthesis to each sampling date, was calculated as in the SIMCOT c o t t o n model (McKinion et al., 1975). (1) When maximum temperatures were above 30 ° C, they were taken as 30 ° C. (2) Average day and night temperatures (TD and TN) were calculated from maximum and minimum temperatures (TMAX and TMIN) by using the empirical factors 0.77 and 0.19, as follows: TD = TMIN + 0 . 7 7 . ( T M A X - T M I N ) TN = TMIN + 0 . 1 9 - ( T M A X - T M I N ) (3) Day-degrees above the threshold of 12 ° C were separately calculated for day and night and weighted by day and night lengths. (4) The sum of day-degrees was divided by 14, thus making a 'physiological day' equivalent to one day with a constant temperature of 26 ° C. The physiological age at each sampling date is also given in Table I. The sampled bolls were dried in a ventilated oven at 80 ° C for 1 week, and each boll was individually weighed. Seed cotton and burs were weighed separately in Galon and Yavne, whereas data for whole bolls only were available for EinShemer. RESULTS AND DISCUSSION
A very high variation in the weight of dry matter was found among individual bolls in each sample. Obviously, most of these bolls did n o t develop to their full potential weight. Therefore, the two heaviest bolls in each sample were chosen to represent, as nearly as possible, the potential development of boll weight. In order to remove the effect of temperature, the time-scale was expressed
172 TABLE I Dates of sampling, and 'physiological age' (PA) from anthesis at each sampling date Location
Tagging date
Sampling date and physiological age
Yavne
June 30
Date: PA:
July 11 9.8
July 23 19.7
Aug. 22 48.7
Aug. 31 56.4
Sept. lO 65.4
Galon
June 24
Date: PA:
July 4 9.0
July 18 21.7
July 28 30.9
Aug. 41.0
8
Aug. 18 50.2
Galon
July 4
Date: PA:
July 18 12.7
July 28 21.9
Aug. 8 32.0
Aug. 18 41.2
Aug. 29 50.9
Ein-Shemer
July 7
Date: PA:
July 19 10.1
July 26 16.1
Aug. 2 22.2
Aug. 10 29.1
Aug. 16 34.8
Date: PA:
Sept. 5 51.1
Sept.12 56.9
Sept.19 62.2
Sept. 27 67.6
as 'physiological age' from anthesis (see Table I). This assumes that the effect of temperature on growth-rate is linear in the range of 12--30 ° C. Mutsaers (1976b) found an exponential effect of temperature on the rate of boll growth, but in the range of temperatures encountered at the three locations during boll development (17--22 ° C minimum and 28--32 ° C maximum) the deviation of the linear function from the exponential one is negligible. The use of a temperature-dependent time-scale makes it possible to find a boll growth curve c o m m o n to all the locations and tagging dates used in this study. Data for the 'potential' weight of dry-matter of seed-cotton (from the two heaviest bolls in each sample) are given in Fig.1. The sigmoid function could be fitted to these data. The weight of seed cotton per boll in g, Ws, at physiological age T, and the growth rate d W s / d T are as follows: Ws = A/(1 + B . E X P ( - C . T ) )
(1)
d W s / d T = C. Ws" ( 1 - Ws/A)
(2)
By using the least-squares method to fit this function to the data, the following estimates of the parameters were found: A = 9.455, B = 54.31, C = 0.1467 The theoretical growth curve, using Eqn. (1) with these parameters is given in Fig.1. Data for bur weight of the two heaviest bolls in each sample, given in Fig.2, indicate a linear increase in bur weight until the age of 21 physiological days. The growth rate was 0.145 g/physiological day during this period. After that, there was a slight decrease in bur weight, and it remained constant later on. The linear phase of bur growth coincided with the rapid increase in boll volume, and ended when the boll reached its final size, as was also noted by Benedict et al. (1973) and Leffler (1976). The subsequent decrease in bur weight was
173
8~
Z~ GALON
~
"
rn
T
1
T--T
1 W
1"
|
o
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0
10
L
l
I
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
70
c) o',q
I
10
I
I
I I i
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
Fig. 1. Potential weight of seed-cotton, weight of dry matter, g/boll: calculated growth curve and validation points. Fig.2. Potential weight of burs, weight of dry matter, g/boll: calculated growth curve and validation points. also observed by Mogilner et al. (1965) and Mutsaers (1976a). It was probably caused by translocation of carbohydrates from the burs to the rapidly growing seeds and fibers (Mutsaers, 1976a). This can be included in the model of boll growth b y assuming a maximum rate of boll growth of 0.28 g per physiological day, limited by carbohydrate supply to the whole boll. This is an empirical parameter that gave the best fit to our data. When the potential growth rate of the seed c o t t o n exceeds this maximum, a decrease in bur weight occurs. The growth rate of the dry weight of the burs (WB) may therefore be expressed as follows: t MIN (0.145; 0 . 2 8 - d W s / d T )
1 <~ T <~ 21
(3)
dWB/dT =
MIN (0
; 0.28-dWs/dT)
21 < T
The theoretical growth curve of the burs, using these equations, is given in Fig.2. At the physiological age of 22--33 days growth rate of seed cotton was higher than 0.28, and consequently the growth rate of burs was negative during this period. A fairly good fit to the observed data was obtained (Fig.2) and the growth curve resembled that postulated by Mutsaers (1976a). The potential growth curve of whole bolls (seed-cotton plus burs) may be calculated b y using the above assumptions. This curve and the actual data for the three locations are given in Fig. 3. The actual ratio of burs in the whole bolls was calculated for the whole samples (average bolls) and also for the t w o largest bolls; these did n o t differ significantly. The results for average bolls are given in Fig.4. The theoretical ratio of burs in the whole bolls, calculated by
70
174
12
r [] YAVNE A GALON
7
T
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r
A 0.8~
O EIN-SHEMER
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U YAVNE
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0.2
L. . . . .~ . I • __ 20 30 40 50 BOLL AGE IN PHYS. DAYS
I
0
10
l
I
60
70
R
~
10
_
I
I
I
I
20 30 40 50 BOLL AGE IN PHYS. DAYS
I
60
70
Fig. 3. Potential weight of whole bolls, weight of dry matter, g/bolh calculated growth curve and validation points. Fig.4. The ratio of bur weight to whole boll weight, calculated and real data.
using the above equations, also given in Fig.4, was very close to the actual ratio. The average boll weight in each sample was in the range of 65--85% of the calculated potential boll weight (Fig.5). Most of the bolls probably did not attain their potential weight because of moisture-stress, carbohydrate-stress, nitrogen-stress, or other stresses that may affect the whole plant or sites of individual bolls. The average boll weight at Ein-Shemer was lower than at the other two locations, probably because of the large number of bolls carried by the plants. There were 87 bolls/m 2 at maturity at Ein-Shemer, as compared to 72 and 32 at Yavne and Galon, respectively. 09--
[
T
T
]
[] YAVNE A GALON O EIN-SHEMER O A
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~
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O
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7
A
A
A
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O
0 0
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I__ I _ I _ I ] 20 30 40 50 60 BOLL AGE IN PHYS. DAYS
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Fig. 5. The ratio of average weight of whole bolls to their calculated potential weight.
175
The general principles of modelling boll growth, as outlined above, may probably be applied to any cultivar of upland cotton. However, the actual values of the parameters (A, B, C in Eqns. (1) and (2); 0.145, 0.28, 21 in Eqn. (3)) are true only for 'Acala SJ-l' and closely related cultivars, and should be empirically adjusted for any other cultivar. The temperatur~related time-scale used gave good results in the mild temperature conditions of our observation fields. However, it may presumably have to be somewhat modified for conditions of extremely high or low temperatures. ACKNOWLEDGEMENT
The assistance of Mr. E. Kletter and Mr. A. Goren, and the help of the cotton growers at the three farms, are gratefully acknowledged. This research was financed by the Cotton Production and Marketing Board of Israel.
REFERENCES Benedict, C.R., Smith, R.H. and Kohel, R.J., 1973. Incorporation of '4C-photosynthate into developing c o t t o n bolls, Gossypium hirsutum L. Crop Sci., 13: 88--91. Gipson, J.R. and Ray, L.L., 1970. Temperature-variety interrelationships in cotton. Cott. Grow. Rev., 47: 257--271. Gutierrez, A.P., Falcon, L.A., Loew, W., Leipzig, P.A. and Van Den Bosch, R., 1975. An analysis of cotton production in California: a model for Acala c o t t o n and the effects of defoliators on its yields. Environ. Entomol., 4: 125--136. Leffler, H.R., 1976. Development of c o t t o n fruit. I. Accumulation and distribution of dry matter. Agron. J., 68: 855--857. McKinion, J.IVL, Baker, D.N., Hesketh, J.D. and Jones, J.W., 1975. SIMCOT II: a simulation of c o t t o n growth and yield. ARS-S-52, USDA, pp. 27--82. Mogilner, I., Turn, B. and PUatti, O.F., 1965. La distribucion de nitrogeno, fosforo y calcion en carpellos y semillas durante la formacion del fruto del algodonero. Phyton, 22: 127-130. Morris, D.A., 1964. Variation in the boll maturation periods of cotton. Cott. Grow. Rev., 41: 114--123. Mutsaers, H.J.W., 1976a. Growth and assimilate conversion of cotton bolls (Gossypium hirsutum L). 1. Growth of fruit and substrate demand. Ann. Bot., 40: 301--315. Mutsaers, H.J.W., 1976b. Growth and assimilate conversion of cotton bolls (Gossypium hirsutum L). 2. Influence of temperature on boll maturation period and assimilate conversion. Ann. Bot., 40: 317--324. Schubert, A M . , Benedict, C.R., Berlin, J.D. and Kohel, R.J., 1973. Cotton fiber development - - kinetics of cell elongation and secondary wall thickening. Crop Sci., 13: 704--709. Stapleton, I-LN., Buxton, D.R., Watson, F.L., Nolting, D.J. and Baker, D.N., 1973. Cotton: a Computer Simulation of Cotton Growth. Agric. Exp. Stn, Univ. Arizona, Tech. Bull., 206, 124 pp. Thornley, J.H.M. and Hesketh, J.D., 1972. Growth and respiration in cotton bolls. J. Appl. Ecol., 9: 315--317. Wallach, D., 1978. A simple model of cotton yield development. Field Crops Res., 1 : 2 6 9 - - 2 8 1 Yfoulis, A. and Fasoulas, A., 1973. Interaction of genotype and temperature on cotton boll period and their implication in breeding. Exp. Agric., 9: 193--201.