Time of emergence determines the pattern of dominance of rice tillers

A large number of later-initiated tillers of semidwarf rice cultivars become either less- or un-productive at maturity. Rice cultivar Lalat was grown in pot (2001-02, Sambalpur University) and field (2004, Regional Research and Technology Transfer Station, Chiplima). The phenological and morphological development, assimilate contents and grain yield of the panicle of different categories of tillers were assessed in order to find out the bias against development of the less productive tillers. The order of dominance of the tillers decreased acropetally in both the conditions. In contrast to the field, the plant tillered profusely in pots. The duration of vegetative and reproductive periods of the late-initiated tillers were short as events like tiller emergence, booting and anthesis were delayed in them, but maturity date was more synchronized. Among tillers, panicle grains yields and assimilate concentration decreased with durations of vegetative and reproductive growth. The concentration of soluble sugars was highest at anthesis and differed among the classes of tillers with lower concentration in the late-initiated tiller compared with the early-initiated tillers. The concentration of soluble sugars at anthesis correlated positively with grain yield. Absence of late-tillers in the field-grown plants increased dominance of early-tillers and prompted higher partitioning of assimilates to panicle at crucial stages like booting and anthesis for benefit of grain yield. In contrast, late-emerged tillers of the potted plants having biomass less than 2.5 g possessed poor sink organogenesis and failed to use assimilates partitioned in their favour to achieve reasonable grain filling.