Yoshida und Hara - 1977 - Effects of air temperature and light on grain fill

Temperature <strong>and</strong> Light on Rice Grain Filling 101
the lowest (16°0) <strong>and</strong> the highest (34°0) day <strong>temperature</strong>, 87 <strong>and</strong> 82 percent, respectively.
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Effect <strong>of</strong> <strong>temperature</strong> <strong>and</strong> <strong>light</strong> on grain filling
Grain growth curve. While <strong>light</strong> intensity did not affect the length <strong>of</strong> the grain filling
period in the upper grains, it affected the grain weight <strong>of</strong> IR20 rice (Fig. 4) <strong>and</strong> <strong>of</strong>
Fujisaka 5 rice (Fig. 5). The length <strong>of</strong> the grain filling period in the whole panicle
grains was increased by 5 days at a high <strong>light</strong> intensity for IR20 rice only, but it was
extended by 10 <strong>and</strong> 5 days at a low <strong>light</strong> intensity for IR20 <strong>and</strong> Fujisaka 5, respectively.
This suggests that low <strong>light</strong> intensity may delay the ripening <strong>of</strong> the whole panicle grains,
probably because <strong>of</strong> a limited supply <strong>of</strong> assimilates to grains on lower branches.
The effect <strong>of</strong> <strong>light</strong> intensity on grain weight was more pronounced on the grains <strong>of</strong>
the whole panicle than on the upper grains, because all <strong>of</strong> the grains (filled <strong>and</strong> unfilled)
were used to measure the average weight <strong>of</strong> the whole grains <strong>and</strong> the low <strong>light</strong> intensity
increased the percentage <strong>of</strong> unfilled grains at the lower branches (Fig. 6).
To <strong>und</strong>erst<strong>and</strong> better how <strong>light</strong> intensity affected grain filling <strong>of</strong> the whole panicle,
sample grains were collected from primary branches at different positions. Similar
UPPER GRAtlS
2~~======::! ~=====::
20
I~
10
°O~--~~--~20~--~~--~~~ O~--~O~--20~---~~
Days orlef rlcooorinQ
Fig. 5. Grain growth <strong>of</strong> upper grains <strong>and</strong> whole panicle in Fujisaka 5
rice <strong>und</strong>er two levels <strong>of</strong> <strong>light</strong> intensity <strong>and</strong> <strong>temperature</strong>.