Relationships between Environmental Conditions and Production-and Consumption Activities of Individual Leaves in the Population of Rice Plant in a Paddy Field : III. Effects of shading on photosynthesis and dark respiration of individual leaf of different position

[摘要] Changes of photosynthetic and respiration rates of leaves of different position under full light and shading conditions and of their recovery processes from shading to full light were investigated. 1. The photosynthesis under shading (about 95% shaded; maximum light intensity under shading was about 6 klx) was about 20% of that under full light, and the ratio of photosynthetic rate under shading to full light condition was higher at the low leaf than at the upper or middle leaf, and it declined in all leaves with time of treatment. 2. There was no remarkable after-effect of shading when plants were shaded one or two days and then transferred to full light, but 3 or 5 days' shading retarded the recovery and such a retardation was marked in the low leaf. 3. Respiration rates decreased by shading. The ratios of respiration rate to photosynthetic rate were 8-12% under full light, being larger as the leaf position was lowered, and they were about 26-33% and 36-40% at the upper leaves and the lower leaf, respectively, under shading. In general, respiration rate changed in parallel with the change of photosyntlletic rate under full light condition, and also under shading although to a smaller extent. Even the lowest leaf may not be "parasitic".

[学科分类] 农业科学（综合）