CARBON SOURCE FOR DEVELOPING BOLLS IN NORMAL AND SUPEROKRA LEAF COTTON *

SUMMARY Narrow‐row field experiments were conducted to investigate the importance of leaves near developing bolls as a source of assimilate in normal and superokra leaf cotton (Gossypium hirsutum L.) plants. A small plexiglass chamber was used to enclose individual leaves which were pulsed with 14 CO 2 for 5 min. Leaves were labelled when sink bolls were 10 days old. Despite much smaller leaves at each position (averaging 42% of normal leaf size) the superokra leaves exported similar amounts of 14 C‐assimilate to the primary boll as did normal plant leaves. Primary sympodial bolls of superokra and normal leaf plants received 37 and 41% of their 14 C‐assimilate from subtending leaves, respectively, 38% from the secondary sympodial leaf, and 28.2 and 21.5%, respectively, from the main stem leaf. Although the leaf subtending the boll of superokra plants was much smaller than the subtending normal leaf, the amount of assimilate provided to the boll was 88% of the normal leaf. The differences in assimilate export to a given boll may not be as important in causing fruit abortion in superokra cotton as expected from leaf size considerations.