EFFECTS OF HAND POLLINATION ON GRAIN FILL ING AND PARTITIONING OF DRY-MATTER IN THE SWEET CORN EAR

The reasons for the poor development of grains at the tip of 'Honey Ba ntam 36' sweet corn ears were investigated as related to the partition ing of dry matter within the ear by comparing the effects of 1) open-p ollination (OP) without bagging and 2) hand-pollination (HP) after bag ging. 1. When the plants were shaded during grain formation, tip ovari es of OP ears failed to fill, whereas those of HP ears filled resultin g in a completely formed ear, irrespective of shade treatment. 2. HP e ars had more filled grains and shorter unfilled tips, as compared with OP ears. The HP ears weighed more at 98 days after sowing than did th e OP ears. 3. HP resulted in (i) uniform partitioning of dry matter wi thin the ear, (ii) promotion of sink-activity in the ear, and (iii) gr eater translocation of assimilates from stem to the ear. The developme nt of poorly ripened grains was due not only to a decrease of dry matt er accumulation during grain enlargement, but also to the lack of part itioning of assimilates to the tip position on the ear. It seems that the partitioning of dry matter within the ear is related to the pollin ation/fertilization of the floret as well as the floret position on th e ear.