Fig. 2. Relationship between final stem length and stem dry weight at grain harvest in sunflower plants that received sunlight red light/far-red light (R/FR) ratios (1.1, control) or low R/FR ratios (0.3) at the stem. Data include three genotypes (Guayacán II, Dekalb G100, and MA 566) and two sowing dates (25 Oct. 1998 and 6 Jan. 1999). Regression line corresponds to least squares fit significant at P < 0.01.