This study was conducted to determine the effects of soil water deficit on the seed yield and the yield components of safflower plants. Four plants were grown in a 1/200O a Wagner pot containing soil, chemical fertilizer and compost. Ample amount of water was supplied before the completion of differentiation of an lateral buds (May 27). After this stage, water was supplied to reach a level of 90%, 60% or 40% of the maximum water-holding capacity of the soil, twice a day. The results obtained were as follows. 1. Water deficit treatments inhibited the internode elongation of the main stem, resulting in a short main stem, and inhibited strongly the growth of lateral buds at the lower nodes (Table 1). 2. The number of leaves, number of bracts and total number of leaves and bracts in the main stem were not affected by soil water deficit. In the uppermost branch, reduction in the soil water content did not affect the total number of leaves and bracts, but the number of leaves decreased, though not significantly, and the number of bracts increased in the 40% plot (Table 2). 3. Soil water deficit decreased significantly the mean area of leaf and bract and the total area of leaves and bracts of the plant (Table 3). 4. Soil water deficit at a level of 40% of the maximum water-holding capacity of the soil delayed the flowering of the heads of the uppermost branches, while no effects were observed on the flowering of the head of the main stem (Table 4). 5. The number of seeds and seed yield (dry weight) per plant were considerably decreased by soil water deficit, whereas the number of florets, percentage of ripened seeds, number of seeds and seed dry weight per head were not affected (Table 6). It was evident that the decrease in seed yield per plant was caused by the decrease in the number of heads per plant, which resulted from the decrease in the number of branches. It was also shown that water deficit inhibited more strongly the development of branches, leaves and bracts than the ripening of the seeds (Table 5).
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