PRODUCTIVITY OF HIGH-YIELDING CROPS .3. ACCUMULATION OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE AND CHLOROPHYLL IN RELATION TO PRODUCTIVITY OF HIGH-YIELDING CROPS

By using high-yielding varieties (lines) of several crops or applying coated urea, which releases nitrogen slowly, it was possible to achieve a very high yield corresponding to that recorded in Hokkaido, Japan. In this report, the accumulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and chlorophyll was investigated in leaves in relation to the productivity of high-yielding crops, including rice, winter wheat, maize, soybean, and potato. The following results were obtained: 1) The amounts of Rubisco and chlorophyll contained in the leaves of each crop at successive growth stages were larger in the ''high yield'' treatment (by using high-yielding varieties or by applying coated urea) than in the ''standard yield'' treatment (by using standard-yielding varieties or conventional cultivation methods). 2) Crop growth rate (CGR) was expressed by the following formula: CGR = (CGR/Rubisco) X Rubisco, where Rubisco is the amount of Rubisco, and CGR/Rubisco is expressed as CGR (Rubisco). As the CGR (Rubisco) value was not always high in the high-yielding crops compared to standard-yielding crops, CGR (Rubisco) was not considered to be the main factor controlling CGR. 3) Among the high-yielding crops, the amount of Rubisco was in the order of rice < maize < soybean < potato < winter wheat during growth. Based on the above results, it is considered that it is very important to keep the amount of Rubisco and of chlorophyll high until the late ripening stage in order to achieve high yields in these crops.