Influence of water deficit and nitrogen limitation on the phenotypic plasticity and root-shoot partitioning in rice cultivars
1995
Regmi, K.R.
Results showed that reproductive stage drought reduced spikelet fertility, panicle emergence, grain number and grain yield. Under drought, soil water was depleted more rapidly at high N than at low N, due to high tiller number, greater leaf area and more shoot growth prior to the onset of stress. Drought resulted in higher root:shoot ratio and a higher root length density (RLD) at depth. Drought affected the earlier lines IR72 and PSBRc 14 less severely than the later lines IR42 and KDML 105, which has a higher dry weight prior to the stress period. Under drought, RLD increased in deeper layers (40-50 cm) in PSBRc 14, while in IR72, RLD increased at 20-30 cm and subsequently showed greater recovery there upon rewatering. Of the two early cultivars, IR72 showed greater susceptibility to drought, with greater reductions in shoot growth, yield and yield components. The results suggest that an ability to increase RLD at depth was advantageous during reproductive stage drought, and was expressed as greater spikelet fertility and grain yield. Breeders should seek lines with these traits for drought-prone environments. Since IR72 and PSBRC14 were similar in phenology and dry weight in well-watered conditions, but differed in response to drought, they may be suitable as probe lines for drought in a selection nursery. These results support the recommendation of PSBRc14 as a stable line well adapted to drought-prone environments and of IR72 for irrigated environments. Further research is needed to examine more closely why these cultivars differed in water use during drought and how they respond to drought at different growth stages
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