Tiller dominance in rice is dependent on assimilate concentration of the panicle during grain filling

Considerable variation exists in grain production of rice tillers. The pattern of grain production is hierarchical; the yield of each successive tiller decreasing in an acropetal fashion from base upwards. In the present study an attempt was made to elucidate the nature of metabolic dominance of early-formed tillers in rice cuitivar Jagannath during the period of grain filling by comparing the grain yield of panicle and the chemical constituents ofthe flag leaf and panicle of main shoot and primary and secondary tillers. Grain yield of panicle of the main shoot was maximum and the yield decreased acropetally in the tillers of the successive nodes. Growth duration of tillers also declined in the same fashion. The flag leaf of main shoot contained the highest concentration of chlorophylls, carotenoids and proteins among the tillers and the concentration was poor in the newly formed tillers. Similarly concentrations of soluble carbohydrates, free amino acids and starch of the panicle of a relatively new tiller was lower than that of an old tiller. The concentration of these chemicals remained high for a longer duration in an old tiller compared to a new tiller. It is concluded that early induction of senescence and reduction of source area might have depleted the assimilate concentration of the panicle and limited grain yield of a newer tiller than that of an older tiller.