Abstract
In rice, the initiation of tillers is staggered and temporally spaced, but maturity is synchronous. Duration of growth in a later-initiated tiller on a higher culm node is shorter and it contributes less biomass and grain yield. The present investigation attempts to discover the manner in which ordered pattern of senescence in basipetal succession impacts source capacity of tillers in two contrasting rice cultivars, namely Lalat (high tillering) and MGD-106 (medium tillering) during the dry season of 2009 and ascertain how tiller production capacity influences dry matter partitioning and tiller dynamics of the plant. In both the rice cultivars, the progress of senescence among different types of tillers was indicated by gradual decline of photosynthetic pigments, total nitrogen and protein concentrations and increase of lipid peroxidation and peroxidase activity of the flag leaf, which affected photosynthetic efficiency. The effects were more pernicious on the newer tillers compared to older tillers. It was observed that metabolic dominance of the older tillers over newer tillers could be accrued due to higher photosynthetic source capacity of the former than that of the latter. It was concluded that flag leaf of a later-initiated tiller is less tolerant to senescence induced photo-oxidative stress, which decreases both source and sink activities. Increase of tiller number and order in rice increases vulnerability of the later-initiated tillers for oxidative stress and grain filling.
Highlights
Monsoonal rains primarily sustain rice cultivation in the tropics and semi tropics during wet season
We investigated the role played by senescence in the regulation of source capacity for grain filling and physiological competence of each class of tiller for metabolic dominance
The results described revealed the hierarchical pattern of dominance between the different classes of tillers of rice plant
Summary
Monsoonal rains primarily sustain rice cultivation in the tropics and semi tropics during wet season. The pattern of panicle development is hierarchical and grain yield becomes poorer in each successive tiller [2]. Panicles of the late-formed tillers on higher nodes do not contribute to grain yield [3]. A high yielding semi dwarf rice plant produces a large number of tillers, one in each successive leaf axil at different time intervals; the initiation and development of the tillers are staggered and temporally spaced, but maturation is synchronous [4]. A late-formed tiller on a higher culm node senesces earlier than that of an older tiller and contributes less in grain number and yield. The physiological mechanism that limits production capacity of tillers and suppresses biomass production and grain yield potential of rice is poorly understood. Besides we know very little about the impact of tiller production capacity on management of biomass distribution between plant parts
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