Contribution of leaves and bracts to the seed yield and yield components in safflower plants (Carthamus tinctorius L.).

Abstract

Leaves and/or bracts of safflower plants were removed at the first flowering stage of the head of the main stem, for the purpose of obtaining information as to the contribution of leaves and bracts to seed yield and yield components, i.e. number of seeds per head and 100-seed-weight, during maturity. The results are summarized as follows : 1. The area of bracts is only 5% of the total area of leaves and bracts in the main stem, but it reaches about 50% in the branches. The ratio in the whole plant was about 14% (Table 1). 2. At the maturity, stems, leaves and heads accounted for about 25%, 15% and 60% of the total dry weight, respectively. Removal of leaves and/or bracts decreased the dry weight of heads, especially that of the branches, more remarkably than the dry weight of stems or leaves (Table 2). 3. Removal of leaves or leaves and bracts decreased the seed yield through the reduction of both the number of seeds and 100-seed-weight. Removal of leaves or leaves and bracts affected the seed yield and number of seeds of the head of the branches more remarkably than those of the main stem, and affected 1OO-seed-weight similarly in the head of the main stem and in the head of the branches (Tables 3, 4). 4. All leaves and bracts contributed to the seed yield of the plant by about 70%. When all leaves and bracts were removed, seed yield of 1.3 g was gained. This seed yield was presumably contributed by the stored photosynthates and the current photosynthates during maturity by the other green parts such as the surface of the stem and head. All leaves and bracts contributed similarly, by about 45%, to the number of seeds and 100-seed-weight (Table 5). 5. The contribution of all leaves to the seed yield was as large as 56% when the bracts were present, and much larger, i.e. about 69%, when the bracts were removed. The contribution of all leaves to the number of seeds and 100-seed-weight was 37% and 28%, respectively, when the bracts were present (Table 5). 6. The leaves of the main stem contributed to the seed yield of the plant by about 40%. The contribution of the leaves of the main stem to seed yield, the number of seeds and 100-seed-weight of the plant was larger than that of the branch leaves. The leaves of the main stem contributed not only to the seed yield of the main stem itself but also to that of the branches. Similarly, the leaves of the branches contributed to both the seed yield of the main stem and that of the branches (Table 5). 7. The contribution of bracts to seed yield was rather small, about 8%, when the leaves were not removed, but it was very large, about 35%, when the leaves were removed (Table 5). The contribution of the bracts to 100-seed-weight when the leaves were removed was especially large. It is suggested, therefore, that the bracts have an ability to substitute for leaves in the ripening of seeds.