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Intercepted Solar Radiation during Seed Filling Determines Sunflower Weight per Seed and Oil Concentration

Unidad Integrada Facultad de Ciencias Agrarias (UNMdP)–Estación Experimental Agropecuaria INTA Balcarce, C.C. 276, 7620 Balcarce, Argentina

View larger version (28K): [in a new window]   Fig. 1. Chronogram of radiation treatments (a, d), weight per seed (Ws; b, e), and oil concentration (O; c, f) as functions of thermal time after flowering for the control treatment and Exp. SDT1 and SDT2. For a, d: each horizontal bar indicates the timing and duration of the shading period in thermal time with respect to flowering (0°C d, base temperature = 6°C) for a single treatment. Gray bar: 50% shading intensity, black bar: 80% shading intensity, open bar: no shading (control). For b, c, e, f: lines represent control treatment data adjusted to linear-plateau functions. Vertical bars represent the standard deviation of the mean of three replications.

View larger version (19K): [in a new window]   Fig. 2. Coefficient of determination (r2) corresponding to linear regressions calculated from (a) weight per seed (Ws) and intercepted photosynthetically active radiation (PAR), and (b) oil concentration (O) and intercepted PAR, for different periods of 100°C d during seed filling for Exp. SDT1 and SDT2 (0°C d corresponded to flowering, base temperature = 6°C). Tick labels on horizontal axes of figures correspond to the beginning points of the 100°C d periods. Horizontal lines indicate r2 values corresponding to P 0.01 (r2 0.37 and 0.29 for SDT1 and SDT2, respectively).

View larger version (18K): [in a new window]   Fig. 3. Final (a) weight per seed and (b) oil concentration as functions of cumulative intercepted radiation (PAR) from 250 to 450°C d after flowering for Exp. SDT1 and SDT2. Data points represent values obtained in each experimental plot.

View larger version (26K): [in a new window]   Fig. 4. Weight per seed (Ws) as a function of cumulative intercepted radiation (PAR) per plant from 250 to 450°C day after flowering for Exp. SDT1, SDT2, LDT2a, LDT2b, LDT3, and LDT4. (a) The line represents the relationship established with intercepted radiation < 37 MJ plant-1 (equation in Fig. 3). (b) The regression represents the relationship established with intercepted radiation < 37 MJ plant-1 (equation in Fig. 3) and the horizontal lines represent the maximum Ws calculated for each plant density (Ws = 81.64 - 4.75x). Data points represent values obtained in each experimental plot.

View larger version (24K): [in a new window]   Fig. 5. Oil concentration (O) as a function of cumulative intercepted radiation (PAR) per plant from 250 to 450°C d after flowering for Exp. SDT1, SDT2, LDT2a, LDT2b, LDT3, and LDT4. Line represents the adjusted function. Data points represent values obtained in each experimental plot.

View larger version (32K): [in a new window]   Fig. 6. Observed vs. predicted data of weight per seed (Ws) and oil concentration (O) for Exp. LDT1 (a and b) and LDT5 (c and d). Predicted values were calculated from the functions given in Fig. 4b and 5. Solid lines are the y = x lines and dashed lines show the linear regressions between observed and predicted values.