Studies on the Photosynthesis of Tobacco Plant : III Relation of the nitrogen supply and the growing conditions to the photosynthesis in plant communities in plant bed

[摘要] Following the previous report, two experiments were carried out to analyse further the photosynthesis in plant communities in plant bed. In the first experiment, of which nitrogen supply was changed, the pattern of the photosynthesis-light curves was almost the same irrespective of the treatment, as shown in the previous report (fig. 2). Logarithmically linear relation was also shown between photosynthesis per leaf area and leaf area index (fig. 3). Further analysis of this relation led to the following formula; P=C(SA)α(LA)1-α Where, P : Photosynthesis per seedling in plant community. SA : Plant bed area per seedling. LA : Leaf area per seedling C : Parameter which expresses photosynthetic ability per leaf area in the community where any mutual shadowing does not appear. α : Expornent which expresses the extent of influence of leaf area index on photosynthesis per leaf area. Commenting this formula, the photosynthesis per plant in plant bed community would be decided by spacing at first, and by leaf area expansion at second. In the second experiment, effect of plant growing conditions, such as water, light and temperature, upon the relation between photosynthesis per leaf area and leaf area index were investigated (fig. 4). The effect of these factors was shown as the slope in the above mentioned relation. And the extent of these factors to restrict leaf area expansion was larger in the order of water, temperature and light. As the quality of seedlings becomes worse with the excess increment of leaf area, it is necessary to restrict leaf area expansion through the growing conditions, with which the depression of photosynthesis is brought about.

[学科分类] 农业科学（综合）