Contribution of Pre- and Post-anthesis Photosynthates to Grains in Pearl Millet under Water Deficit

When rains end early, grain yield productivity of pearl millet ( Pennisetum glaucum [L.] R. Br.), a rainfed cereal crop of arid and semi-arid regions is limited by water deficits during flowering and grainfilling. Reserves of assimilates present at flowering and available for later remobilization to the grains, could act has buffer under water deficit conditions during flowering and grainfilling. The contribution of pre- and post-anthesis assimilates to grain yield under water-deficit conditions during flowering and grainfilling was investigated by ¹⁴C labeling of leaves at boot and 10 days after anthesis of field-grown plants. Water deficit resulted in 20 percent reduction to grain yield in the main tiller. The distribution pattern of labeled carbon at harvest in various plant parts in water deficit and irrigated control treatments was similar. About 25 percent of the pre-anthesis assimilates was translocated to the grain at harvest, while 95 percent of the post-anthesis (current) assimilates was translocated to the grain. At grain maturity, about 60 percent of the pre-anthesis assimilate was distributed in inflorescence structures, and in upper three inter-nodes which were the active sinks at boot stage. Post-anthesis assimilates were directed towards the grain development which was the active sink after flowering. In conclusion, about 25 percent of the pre-anthesis assimilates are translocated to the grain at harvest and there was no additional contribution under water deficit and post-anthesis assimilates were primarily translocated to the developing grain.