Physiological aspects of leaf senescence during spikelet fillings in rice (Oryza sativa L.)
1991
Park, Tae-shik
Studies were conducted to investigate cultivar differences in leaf senescence and the effect of sink-source balance, nitrogen level, night temperature, and light intensity on leaf senescence and spikelet filling. Senescence in this experiment was evaluated by the CHL content of the leaves. About 75% of the initial CHL content was reached at 14 days after heading (DAH) in the third leaf from top, 20 DAH in the penultimate (2nd) leaf and 26 DAH in the flag leaf in 20 cultivars and lines. Photosynthetic activity was maximum at 5 DAH and the activity decreased according to age-related CHL loss up to 26 DAH when it reached the minimum level. It was found that the best leaf to use in classifying cultivars is the penultimate leaf at 20 DAH rather than the flag leaf or the third leaf because the flag leaf lose CHL too slow while the third leaf has rapid decrease in CHL. Sink-source balance also affected leaf senescence. Unbalanced sink and source treatments like removing half of the spikelets and cutting half of the leaves had a slower decrease in the CHL content than intact plants. Leaf blades and sheath CHL content, leaf area and leaf dry weight tended to decline faster at low night temperature (32/22 deg C) in Hankang and medium temperature (32/26 deg C) treatment in IR66 than the other treatments at maturity. At low nitrogen (N) level, the effect of shading was small. Rice plants that received low light intensity (35, or 70% shading) exhibited higher leaf CHL content, thinner and wider leaves and higher N content than those under full sunlight.
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