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 achiev e a very high yield corresponding to that recorded in Hokkaido, Japan. In this report, the accumulation of ribulose-1,5-bisphosphate carboxy lase/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 o btained: 1) The amounts of Rubisco and chlorophyll contained in the le aves of each crop at successive growth stages were larger in the ''hig h yield'' treatment (by using high-yielding varieties or by applying c oated urea) than in the ''standard yield'' treatment (by using standar d-yielding varieties or conventional cultivation methods). 2) Crop gro wth rate (CGR) was expressed by the following formula: CGR = (CGR/Rubi sco) X Rubisco, where Rubisco is the amount of Rubisco, and CGR/Rubisc o is expressed as CGR (Rubisco). As the CGR (Rubisco) value was not al ways high in the high-yielding crops compared to standard-yielding cro ps, CGR (Rubisco) was not considered to be the main factor controlling CGR. 3) Among the high-yielding crops, the amount of Rubisco was in t he order of rice < maize < soybean < potato < winter wheat during grow th. Based on the above results, it is considered that it is very impor tant to keep the amount of Rubisco and of chlorophyll high until the l ate ripening stage in order to achieve high yields in these crops.