Source manipulation induced variation in dry matter partitioning to reproductive sink in castor

An experiment on effect of defoliation at different spike initiation stages on biomass partitioning was conducted for two consecutive years during 2005–07 using DCS-9 variety. Treatments consisted of four defoliation levels (25%, 50%, 75% and 100%) at primary, secondary and tertiary spike initiation stages on entire plant along with control, with 3 replications in RBD. With increase in percent defoliation at any stage there was reduction in stem, leaf, capsule dry weight which resulted in significant reduction in total dry matter. There was compensation in growth only up to 25% defoliation at any stage. Only primary seed yield was affected with defoliation at primary spike initiation stage, but with secondary stage defoliation, yield of all order branches was affected. Secondary, tertiary and quarternary seed yield was affected with defoliation at tertiary stage. Yield of one order decreased with >25% defoliation at that order and >50% defoliation at next lower or higher order spikes.