Reproductive growth of maize, sunflower and soybean at different source levels during grain filling

ELSEVIER

Field Crops Research 48 (1996) 155-165

Field Crops _ Research

Reproductive growth of maize, sunflower and soybean at different source levels during grain filling Fernando H. Andrade *, Mafia A. Ferreiro Unidad Integrada EEA INTA Balcarce, Facultad de Ciencias Agrarias UNMP, CC 276 7620 Balcarce, Buenos Aires, Argentina

Received 15 April 1996; accepted 30 July 1996

Abstract

Maize (Zea mays L.), sunflower (Helianthus annus L.) and soybean (Glycine max (L.) Merr.) are sometimes subjected to stress that affects source capacity during the grain filling period. Effects of variations in source capacity during grain filling on yield and its components in these crops were examined with shading and thinning treatments. Shading reduced grain yield in the three crops. Average percent reductions were greatest for sunflower and least for maize. In soybean and sunflower, the number of grains was more affected than weight per grain, whereas the opposite was true in maize. Average grain yield per plant was greatly increased in soybean and sunflower and slightly affected in maize when source per plant was increased by thinning. Grain number was the yield component most affected in soybean and weight per grain in sunflower. Neither treatment affected grain filling rate of maize, whereas shading reduced effective grain filling duration. Contrarily, the source treatments affected the rate of grain filling in sunflower and in soybean. Variations in source capacity during grain filling affected grain quality much more in sunflower and maize than in soybean. In general, thinning treatments resulted in the highest levels of sugars in stems and shading treatments the lowest. Maize would be the crop with the largest capacity to buffer source reductions during grain filling. In conclusion, modification of source capacity during grain filling had more impact on plant yield in sunflower and soybean than in maize and affected grain quality mainly in maize and sunflower. Keywords: Grain filling; Source of assimilates; Stem reserves

1. I n t r o d u c t i o n

Maize ( Z e a m a y s L.), sunflower ( H e l i a n t h u s a n n u u s L.), and soybean ( G l y c i n e m a x (L.) Merr.) are important summer crops of southeast Buenos Aires Province in Argentina, but yield vary widely due to water stress, diseases, defoliations, and other causes. The most critical periods for stress damage are flow-

* Corresponding author.

ering a n d / o r grain filling depending on the species (Andriani et al., 1991; Chimenti and Hall, 1992; Cirilo and Andrade, 1994b). In the Balcarce area, the grain filling period is commonly subjected to stresses such as low temperature and low radiation (Cirilo and Andrade, 1994a), diseases (Pereyra and Escande, 1994), defoliation by insects or hail (Alvarez Castillo, A. personal communication) and water deficits (Andrade and Gardiol, 1994) that reduce the supply of assimilates for reproductive growth. Questions arise about the relative yield stability of these crops, i.e., about their ability to tolerate or

0378-4290/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PII S0378-4290(96)01017-9

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F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

compensate for such stresses. Quantitative comparisons of the response to source-variation during grain filling with the three crops may help clarify possible differences in stability. Source capacity is determined by photosynthesis during grain filling and by carbohydrate reserves (Cliquet et al., 1990; Uhart and Andrade, 1991). Maize usually has more carbohydrate reserves than sunflower and soybean (Egli and Leggett, 1976; Hall et al., 1989; Uhart and Andrade, 1991), and it maintains ground cover and photosynthetic capacity almost up to physiological maturity (Andrade, 1995). In contrast, sunflower generally loses ground cover and photosynthetic capacity rapidly after flowering (Andrade, 1995). Provided that these characteristics are reflected on the source-sink relationships, these two crops would differ in their response to variations in source capacity during grain filling. These variations would affect grain weight in all three crops while grain number would also be affected in indeterminate soybean due to its extended period of flowering (Ritchie et al., 1982). The objective of the present paper is to study for the three crops the effect of variations in source capacity during seed filling on yield and its components.

2. Methods and material Experiments were conducted at the 1NTA Balcarce Experimental Station (37 ° 45' S, 58 ° 18' W, 130 malt.) during the 1992/93 and 1993/94 growing seasons. The effects of shading and thinning during grain filling on yield of the three crops were evaluated. Table 1 presents climatic data for this period. This area is characterized by low average

Table 1 Daily solar radiation and daily mean temperature. Monthly means for the 1992/93 and 1993/94 growing seasons Season

Nov Dec Jan

Feb

Mar Apr

Solar radiation 1992/93 18.1 23.6 20.5 17.9 16.3 9.3 ( M J m -2 day 1) 1993/94 21.7 26.2 24.0 23.6 16.1 10.3 Mean ternp.(°C)

1992/93 1993/94

14.2 19.0 21.0 21.0 20.4 15.4 16.3 19.1 20.3 19.6 18.2 13.8

temperatures during the growing season and a frostfree period of about 150 days. The soil was a Typic Argiudol (USDA taxonomy) with an organic matter content of 5.6%. Maize hybrid Dekalb 636 was sown on 8 October 1992 and 19 October 1993; sunflower hybrid Dekalb G 100 was sown on 14 October 1992 and 22 October 1993; and soybean cultivar Asgrow 3127 was sown on 6 November 1992 and 9 November 1993. Plots were oversown and densities of 8.5 plants m -2 in maize, 5.7 plants m -2 in sunflower and 48 and 34 plants m -2 in the first and second year in soybean, were obtained by thinning after seedling emergence. Uniformly spaced stands were obtained in all plots. The experiment was a split-plot design, with the crops assigned to main plots and the source treatments to subplots. The experiment was conducted with four replications. The size of the subplots was four rows 0.70 m apart and 10 m long. Nutrients and water were not limiting to growth. The crops were fertilized to provide adequate mineral nutrition. Soil water was kept, by irrigation, over 50% of maximum available water in the first metre of depth during the entire growing season. Soil water content was monitored by means of a neutron probe (Troxler 103 A). Weeds and insects were adequately controlled. Three treatments were applied to each crop: (1) 45% uniform shading during grain filling; (2) thinning at the beginning of grain filling to uniform spacing by one-fourth of the original plant density and (3) an untreated control. Plots were shaded with black synthetic mesh cloth stretched just above the top of the crop on cane and wire structures. Shading and thinning were applied from approximately 2 weeks after the beginning of flowering to physiological maturity in maize and sunflower, and from R5 to physiological maturity in soybean stages defined by (Fehr and Caviness, 1977). Thus, all source-variation treatments were applied from the onset of rapid grain growth to physiological maturity. In sunflower, the pericarps of border cypselae were fully grown when treatments were initiated. Percent radiation interception was estimated from photosynthetic photon flux (PPFD) measurements as 1 0 0 [ 1 - (It/Io)], where I t is the incident PPFD at ground level and I 0 is the incident PPFD at the top of the canopy. The values of I t and I 0 were obtained with a LI-COR 188B radiometer (LI-COR, Lincoln,

F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

NE) connected to a line quantum sensor (LI-COR 191 SB). These measurements were taken at noon, a few days after treatment application. The amount of radiation intercepted by each plant was calculated based on incident radiation per unit area, percent interception and plant density. The accumulation of above-ground dry matter was followed during grain filling by taking sequential samples of 10 (maize and sunflower) or approximately 30 (soybean) plants from the central rows every 20 days, leaving borders between adjacent harvests. During the vegetative period, plant dry matter was estimated by taking samples from the control treatments. The samples were separated into stems, leaves and reproductive structures, oven-dried (with air circulating at 60°C) to constant weight, and weighed. Total soluble carbohydrates in stems were determined in each dry matter sample according to Hodge and Hofreiter (1962) after sucrose cleavage. Grain samples were taken every 7 days from the beginning of the treatment periods. In each sampling, a total of 50 kernels or 50 cypselae were taken from five randomly selected plants from the central rows per plot and from two positions of the reproductive structures, the upper and lower third of the maize ear and the peripheral and intermediate (half way between the center and the border) region of the sunflower head. In soybean, a total of 30 pods from plants from the central rows were taken per plot, 15 from the upper third and 15 from the lower third of the canopy. Total above-ground biomass and grain yield (0% moisture) were determined at physiological maturity by harvesting 10 plants of maize and sunflower and 20 to 60 plants of soybean from the central rows of each plot. Nitrogen in grains was determined following method A (without salicylic acid modification) reported by Nelson and Sommers (1973). Grain lipid content was determined by the Standard AOCS method for maize and soybean (AOCS, 1978). Nuclear magnetic resonance analysis (Robertson and Morrison, 1979) was used to estimate lipid content in sunflower. Ash content was determined by weight after complete combustion of the grain sample. Carbohydrate content was calculated as the residual fraction. Yields were expressed per plant to allow comparisons between thinned and unthinned treatments.

157

Grain yield per plant from the control treatments from the 1992/93 growing season was also expressed in glucose equivalents (GE) following Penning de Vries (1974). The ratio between maximal sugar accumulation in stems and grain yield expressed as GE was calculated for the same treatments. Data were processed by analysis of variance procedures and by linear regression analysis. Appropriate standard errors of the means were calculated. When necessary, data were transformed to natural logarithm to obtain homogeneous variances.

3. Results and discussion 3.1. Dry matter production

Shading reduced the amount of radiation intercepted by each plant by approximately 45% for all three crops, and thinning increased it from approximately 100% in maize and sunflower to 130% in soybean. In sunflower, shading accelerated and thinning delayed leaf senescence (data not shown). Shading and thinning significantly affected dry matter accumulation per plant during grain filling and final plant dry matter (Fig. 1). Dry matter losses (specially in soybean and sunflower) and differences in the energetic value of the reproductive growth among the crops did not allow us to obtain reliable estimates of plant growth rates during the grain filling period. Relative effects of shading on final dry matter yield per plant were similar for all three crops. On the other hand, thinning produced different relative effects on this variable depending on the crop. Soybean has the highest plasticity in dry matter production per plant in response to thinning at the beginning of grain filling. 3.2. Grain yield and its components

Alteration of source capacity during grain filling affected grain yield per plant and yield components in all the crops. There was a strong source treatment by crop interaction in both years however (Table 2). Shading during grain filling reduced grain yield per plant in all three crops (Table 3). Average percent reductions were greatest for sunflower and least for

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F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

maize. In soybean and sunflower, grain number was affected more than weight per grain, whereas the opposite was true in maize (Table 3). Average grain yield per plant was greatly increased in soybean and sunflower and slightly af450

O thinning A control • shading

fected in maize when source per plant was increased by thinning (Table 3). Grain number was the yield component most affected in soybean, and weight per grain was most affected in sunflower (Table 3). Sunflower had a high capacity to increase weight per 450

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Fig. 1. Above-ground dry matter accumulation per plant as a function of days after emergence for the different source treatments during grain filling and for the three crops for (A) 1992/93 and (B) 1993/94 growing seasons. Maize hybrid DK 636 (circles); sunflower hybrid DK G100 (squares); soybean cultivar Asgrow 3127 (triangles). Experiments conducted at INTA Balcarce experimental station without water or nutrient limitations. Vertical bars indicate SE. Horizontal bars indicate the treatment period. In soybean, fallen leaves are not included. Daily mean temperatures (average of values taken every hour) within the canopy (not under direct sunlight) did not differ more than I°C among the different treatments.

F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

159

Table 2 Analysis of variance for grain yield, number of grains per plant and weight per grain of maize, sunflower and soybean under different source treatments during grain filling, for (A) 1992/93 and (B) 1993/94 growing seasons. Data were transformed to In X to obtain homogeneous variances SV

DF

(A) 1992/1993 Total 35 Rep. 3 Crop (c) 2 Error a 6 Treat. (t) 2 c. t 4 Error b 18

Yield/plant SS

MS

F

7.75 0.01 7.04 0.009 0.54 0.13 0.019

0.0035 3.5 0.0015 0.27 0.032 0.001

2.28 * 2324 . . . .

5.62 0.02 5.03 0.005 0.47 0.065 0.03

0.008 2.51 0.0008 0.23 0.02 0.0017

8.99 * 2967 . . . .

254 . . . . 30 . . . .

Number of grains/plant

Weight per grain

SS

MS

F

SS

MS

F

11.16 0.06 10.83 0.01 0.21 0.07 0.021

0.002 5.41 0.002 0.11 0.019 0.001

0.88 2323 . . . .

5.47 0.001 5.36 0.005 0.07 0.025 0.005

0.0004 2.68 0.0009 0.037 0.006 0.0003

0.48 3042 . . . .

9.66 0.006 9.43 0.003 0.15 0.07 0.014

0.002 4.71 0.0005 0.07 0.02 0.0008

4.37 10247 . . . .

4.0 0.004 3.88 0.0065 0.1 0.008 0.007

0.001 1.94 0.001 0.05 0.002 0.0004

1.14 1799 . . . .

92.5 . . . . 16.3 . . . .

131 . . . . 22.4 . . . .

(B) 1993/1994 Total Rep. Crop(c) Error a Treat. (t) c •t Error b

35 3 2 6 2 4 18

140 . . . . 9.74 * * *

95 . . . . 21 . . . .

121 . . . . 4.92 * *

Treatments: shading during seed filling; thinning at the beginning of seed filling and an untreated control. * p <0.05; ** p <0.01; *** p <0.001 and . . . . p <0.0001.

g r a i n in r e s p o n s e to a h i g h s o u r c e - s i n k

ratio during

a n d o n l y 3 0 % in m a i z e ( A n d r a d e , 1995). I n s o y b e a n ,

grain filling. In other e x p e r i m e n t s , an 8 0 % r e d u c t i o n

s e e d n u m b e r p e r p l a n t i n c r e a s e d 6 0 % i n r e s p o n s e to

in n u m b e r

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t h i n n i n g e v e n t h o u g h t h i s t r e a t m e n t w a s a p p l i e d at

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treatment that did

ity o f t h i s c r o p .

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weight per

g r a i n ) i n c r e a s e d w e i g h t p e r g r a i n 1 0 0 % in s u n f l o w e r

Grain number was affected more by the different

Table 3 Grain yield, number of grains per plant and weight per grain of maize, sunflower, and soybean under different source treatments during grain filling, for (A) 1992/93 and (B) 1993/94 growing seasons. Source treatment means followed by the same letter do not differ significantly ( p < 0.05) Yield/plant (g)

Number of grains/plant

Grain weight (rag/grain)

A

A

B

A

B

Maize

thinning control shading

170 a 170 a 130 b

147 a 126 b 103 c

482 a 482 a 420 b

B 469 a 448 a 427 a

350 a 350 a 310 b

310 a 280 b 240 c

Sunflower

thinning control shading

100 a 66 b 42 c

110 a 81 b 54 c

1950 a 1710 b 1240 c

1990 a 1760 b 1420 c

52 a 38 b 34 c

52 a 45 b 37 c

Soybean

thinning control shading

22.5 a 11.8 b 8.9 c

27.1 a 14.6 b 11.0 c

110 a 68 b 53 c

145 a 91 b 67 c

206 a 173 b 167 b

190 a 162 b 165 b

160

F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

sunflower, flowering is sequential and proceeds from peripheral to central portions of the head (Connor and Sadras, 1992). By the time of treatment application, the central cypselae were in an early reproductive stage and more susceptible to abortion than the peripheral ones. This effect would have been more

source treatments in sunflower and soybean than in maize. In maize, kernel number per ear is related to crop growth rate during 2 to 3 weeks after flowering (Tollenaar, 1977; Kiniry and Ritchie, 1985; Cirilo and Andrade, 1994b). Thus, kernel number was practically fixed by the time treatments were begun. In

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Fig. 2. Dry matter accumulation per grain as a function of time for maize (circles) (upper and lower third of the ear); sunflower (squares) (peripheral and intermediated positions on the head; and soybean (triangles) (upper and lower third of the canopy) for the different source treatments during grain filling during (A) 1992/93 and (B) 1993/94 growing seasons. Vertical bars indicate SE. For more details see legend of Fig. 1.

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Fig. 2 (continued). important in late plants. Accordingly, Cardinali et al. (1982) reported that defoliation from the beginning of rapid seed growth produced abortion of cypselae at the center of the head. The strong overlap of pod formation, seed set, and seed filling periods in soybean allowed shading or thinning from the beginning of seed filling to have a strong impact on the number of seeds. Vasilas et

al. (1989) also found that the number of seeds was reduced by defoliation at R5. 3.3. Dry matter accumulation p er grain

The time courses of grain growth for the three species are illustrated in Fig. 2. In maize, grain filling rate (during the linear phase of grain filling)

162

F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

was not affected by the source treatments. This variable is mainly a function of temperature (Cirilo and Andrade, 1996). The average rate was 8.3 +__0.32 mg d a y - 1 grain- t for grains in the lower third of the ear. Final weight per grain was less with shading because the effective grain filling period was shortened by a delay in the onset of the linear phase of filling (1992/93) or by an earlier physiological maturity (1993/94). Similar trends were observed for both positions in the ear. Daynard and Duncan (1969) found similar effects in response to defoliation. In sunflower, the rate of grain filling was affected by source treatments. The largest effects were observed for cypselae located at an intermediate position on the head. Filling rates for those cypselae were 0.47 _+ 0.03, 0.80 + 0.08 and 1.06 ___0.08 mg day -1 grain - l for shading, control and thinning treatments, respectively, for the first year, and 0.90 _+ 0.20, 1.34_+0.07 and 1.89_+0.15 mg day - l grain - l , in the second year. The higher rates observed for the second growing season would be explained by higher radiation levels during most of grain filling (see February in Table 1). Cypselae located at an intermediate position on the head weighed around 10 mg and those located near the border around 20 mg at the time of treatment application. Most of this weight corresponded to the pericarp that was fully grown for border cypselae at that time. Grain filling duration appeared not to be prolonged by increased in assimilate supply. In the second year, samples were taken only up to physiological maturity because of disease problems (Sclerotinia sclerotiorum). In soybean, the pattern of dry weight accumulation per seed was affected more by thinning than by shading. Average filling rates for seeds located in the upper third of the canopy were 5.5 _+ 0.16, 6.1 _+ 0.27, and 7.7 + 0 . 1 3 mg day -1 grain -1 , for the shading, control and thinning treatments, respectively (rates were 24% greater in the second year than in the first). Thinning also appeared to increase the duration of seed filling in this portion of the canopy. Egli and Crafts Brandner (1996) also reported that soybean seed filling rate and duration were affected by changes in assimilate supply during seed filling. Seeds located on the upper part of the plant were lighter than those located in the lower third of the plant at the beginning of the treatment

Table 4 Nitrogen and lipid concentrations (percentage of dry matter) in mature grains of maize, sunflower and soybean in response to different source treatments during grain filling for two growing seasons. Means followed by the same letter do not differ significantly within each crop ( p < 0.05) Nitrogen (%DM)

Lipid (%DM)

1992/93

1992/93

1993/94

thinning 1.73 a control 1.41 b shading 1.21 c

1.68 a 1.34 b 1.30 b

4.24 a 3.88 a 4.05 a

4.07 a 4.15 a 3.97 a

Sunflower thinning 2.86 b control 2.73 b shading 3.28 a

2.81 b 2.78 b 3.32 a

48.30 a 46.50 a 39.10 b

50.90 a 49.70 a 44.70 b

Soybean

6.32 a 6.02 b 6.04 b

19.30 a 19.00 a 19.20 a

18.90 a 18.30 ab 17.90 b

Maize

thinning 6.42 a control 6.12 b shading 6.11 b

1993/94

period because, at that time, they were at an earlier reproductive stage. Final weight was greater for the upper seeds, however, because of a greater seed filling rate, probably explained by their better position in the canopy. Final weights per grain presented in Fig. 2 were obtained from specific regions of the plant (see Section 2) thus, they do not coincide with values obtained from the whole plant presented in Table 3. The most striking differences occurred for sunflower because values obtained from the whole plant included light cypselae located towards the center of the head that were not considered in Fig. 2.

3.4. Grain quality The effects of variation in source during grain filling on nitrogen and lipid concentration in grain may be seen in Table 4. In maize, increases in the source of assimilates during grain filling increased nitrogen percentage. This agrees with data reported by Uhart and Andrade (1995) who found a linear and positive association between kernel nitrogen concentration and source/sink ratio during grain filling. Contrarily, lipid percentage in maize was not affected by the treatments. In sunflower, decreases in assimilate supply during grain filling decreased lipid concentration and increased nitrogen concentration in cypselae. Reduc-

163

F.H. Andrade, M.A. Ferreiro / Field Crops Research 48 (1996) 155-165

tions in source had less impact on protein accumulation, which was more complete when treatments were applied and could rely to a large extent on nitrogen remobilization (Cetiom, 1983). Thus, protein was diluted in the grain as the availability of assimilates during the linear phase of seed filling became less limiting for oil synthesis and seed growth. These observations agree with data reported by Cetiom (1983) and Connor and Sadras (1992). Thinning did not significantly affect nitrogen or lipid concentration in cypselae. In soybean, relative effects of the source treatments on seed composition were much smaller than in the other crops. Thinning increased nitrogen but not lipid concentration, whereas shading did not have any effect on seed quality. 3.5. S t e m reserves

Soluble carbohydrate concentration in stems was affected by the source treatments (Fig. 3). In general, thinning resulted in the highest levels of sugars in stems and shading treatments the lowest. Maximum soluble sugar concentration in stems of control treatments was around 28% of stem dry matter in maize, almost 7% in sunflower and 3.6% in soybean. The reduction in soluble carbohydrate concentration in stems of maize and sunflower began at the onset of rapid grain growth and was smaller as source per plant increased. In soybean, these decreases occurred at later stages of seed growth. Increments in source per soybean plant increased sugar accumulation in stems during the first part of the grain filling period. Later, remobilization per plant was greatest for the thinning treatment. Similar patterns of sugar concentration in stems during grain filling for control treatments were presented by Uhart and Andrade (1991) in maize, and Egli and Leggett (1976); Antos and Wiebold (1984) in soybean. Contrarily, sugar concentrations in sunflower control treatment were somewhat less than those reported by Hall et al. (1989). Maximal amounts of soluble sugars in stems of control plants were 29.9 g plant-~ in maize, 4.6 g plant-1 in sunflower, and 0.3 g plant i in soybean. These values represented 14, 3.5, and 2% of the glucose equivalents required for synthesis of reproductive biomass in control plants of maize, sun-

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Fig. 3. Soluble carbohydrateconcentration in stems as a function of days after emergence for maize (circles); sunflower (squares) and soybean(triangles) for the different source treatments during the 1992/93 growing season. Vertical bars indicate SE. Arrows indicate the beginning of the treatment period.

flower and soybean, respectively. Soluble sugars are an important source of reserves in stems and the stem is the main reserve organ in the three crops (Ciha and Brun, 1978; Streeter and Jeffers, 1979; Setter and Flannigan, 1986; Hall et al., 1989). Thus,

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maize would be the crop with the largest capacity to buffer source reductions during grain filling. Most stem reserves can be remobilized or used for stem maintenance respiration as indicated by small final values of percent soluble sugars in stems from shaded treatments. The shaded plots also provide an idea of m a x i m u m remobilization from stems (or from reserve tissues). Final values of sugar in stems of the control treatments of sunflower and soybean were similar to those of shaded treatments (Fig. 3). On the other hand, in maize, control values were twice those of the shaded plants. The ratios of final sugar concentrations in control and shaded treatments were 2.06; 1.04 and 1.09 for maize, sunflower and soybean, respectively. These data indicate, for the conditions of these experiments, that source-variations during grain filling were more important in sunflower and soybean than in maize. This agrees with the fact that the different source treatments during grain filling had less impact on grain filling rates and yield of maize than they had on filling rates and yields of the other crops.

4. Conclusions Modification of source capacity during grain filling had more impact on plant yield in sunflower and soybean than in maize. The source treatments presented strong effects on grain quality in maize and sunflower but not in soybean. According to these results, sunflower and soybean yields would be more dependent than maize on the crop condition during grain filling. Considerable intraspecific genetic variability is expected for each of the traits considered here. The cultivars used in these experiments do, however, represent the general features of maize, sunflower, and indeterminate soybean adapted to the southeast of Buenos Aires province.

Acknowledgements This work was supported by Instituto Nacional de Tecnologla Agropecuaria, Consejo Nacional de Investigaciones Cientfficas y Trcnicas, Dekalb Argentina SA, F u n d a c i r n Antorchas and the Facultad

de Ciencias Agrarias de la Universidad de Mar del Plata. The authors want to thank E. Cacace for his help in sugar analysis.

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