Abstract
Leaf fresh weight per unit area (FW/dm2) was already reported to be significantly correlative with photosynthetic rate (P/dm2) in upper leaves, but it became less correlative as leaf position lowered to end in non-correlative in primary leaves. The experiment was carried out to confirm the above mentioned result with primary leaves and also to get the information about RuDP carboxylase activity (RuDPact/FW) in primary leaves. The results, including the informations about upper leaves, were summarized as follows. 1. P/dm2 was devided into the following two components : P/dm2=FW/dm2×P/FW. where P/FW is photosynthetic rate per unit fresh weight of leaves. In primary leaves, FW/dm2 was again non-correlative with P/dm2,but P/FW was highly and significantly correlative. Significant correlation between P/dm2 and RuDPact/FW supported the relationship between P/dm2 and P/FW. 2. As leaf position decame higher, leaves tended to be thinner and the correlation coefficient between P/dm2 and FW/dm2 got higher. The coefficient between P/dm2 and P/FW, on the contrary, got lower. This was confirmed also by the change of coefficient between P/dm2 and RuDPact/FW. 3. In lower leaves, photosynthetic activity per unit amount of leaf mesophyll seems to be an important factor for varietal differences in photosynthetic rate. In upper leaves, on the contrary, amount of leaf mesophyll per unit leaf area becomes more important. In the breeding of soybean plant for higher photosynthetic rate, FW/dm2 of upper leaves may be used as a character for selection.
