Vergara - 1976 - Physiological and morphological adaptability of ri

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Clirrlutic productivity l l/hnl
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6. Relationship between climatic productivity index attd
solar radiation and tentpcrature during the period of 25
days before llotvering at Lot-i Baflos, Philippines (‘foshida
and Parao. 1974}.
shading treatment during the vegetative stage varied from 2S6 gfsq cm under
100% sunlight to I01 g/sq m under 25 >< sunlight. This difference, hotvever. did
not have a noticeable effect on spikelet number per square meter and hence on
frield when the plants were exposed to normal sunlight during the reproductive
stage. Crops shaded during the vegetative stage had smaller crop size and lower
LAls and hence had better light penetration than the control during the
reproductive stage. Thus the better light environment of the crops must have
compensated for the smaller crop size in spikelet formation during the reproductive
stage.
In the next 25 days. i.e. the reproductive stage. however. shading had a very
pronounced effect on spikclct number and hcncc on yield. Spikclct number per
square meter was positiveh" and linearly correlated ‘Nlill drix-matter production
during the reproductive stage (r = (l.9‘)4**). It was also linearly correlated with
incident solar radiation during the same period (Fig. 3A). This would imply that
spikelet number is simply linked with photosynthetic production during the
reproductive stage.
Shading during the ripening period also reduced grain yield considerably‘. This
reduction in yield can largely be attributed to decreased filled-grain percentage.
Utifillcd grains were divided into unfertilc grains and partially filled grains.
Examination of unfilled grains shtiwed that decreased filled-grain percentage