Abstract
A dwarf type of beans (Phaseolus vulgaris) was used for these experiments. They were planted on the field in different spacing (10×10 cm, 30×30 cm) and were applied different amount of fertilizer. The structure of leaves grown under such growing conditions was investigated microscopically. So far as these experiments were concerned, the difference of fertilizing made no effect on the structure of leaves, but the difference of spacing made a conspicuous effect, although fertilizing increased leaf size markedly. The leaves grown under closer spacing reduced their thickness and had sparse arrangement of mesophyll cells and broader areoles compared with the ones grown under thinner spacing. The development of these leaves were investigated anatomically and it was revealed that such differences occurred at the time when the leaf began to expand rapidly. Before this stage and when the cell division prevailed over the leaf, no difference was to be observed between the leaves grown under different growing conditions. The structure of leaves grown under closer spacing coincides with the structure of so-called "shade leaf". Under closer spacing, the light intensity at the level of growing point was 60∼70 per cent of that of thinner spacing. Therefore, it is inferred that the main factor which produces change of leaf structure above mentioned may be light intensity. Shading treaments gave the same effect on the structure of leaves as that of closer spacing, and moreover it is found that the shading at the expanding stage was most effective in causing the change of leaf structure.
