REDISTRIBUTION OF CARBON AND NITROGEN-COMPOUNDS FROM THE SHOOT TO THE HARVESTING ORGANS DURING MATURATION IN FIELD CROPS

The present paper aims at determining how carbon (C) and nitrogen (N) compounds are redistributed from leaves to harvesting organs during maturation in several major field crops. In order to illustrate these processes in the case of C and N compounds, 6 major crops in Hokkaido were grown and compared during maturation. The results obtained were as follows. 1) The N-redistribution rate during maturation was in the order of wheat, soybean and potato > maize > rice. The percentage of distributed nitrogen among the different nitrogenous fractions in leaves and stems was remained constant during maturation, suggesting that each nitrogen compound was equally decomposed. 2) The composition of protein amino acids was similar regardless of organs or crops. The composition of free amino acids differed widely among organs and crops, and differed from that of protein amino acids. Therefore during the translocation of amino acids from leaves to harvesting organs through stems, the composition of free amino acids was almost reconstructed in all the crops. 3) Dry weight of leaves and stems during maturation increased in rice, wheat and maize, but decreased in soybean and potato. The proportion of cellulose and hemicellulose in leaves was high in rice, wheat and maize and low in soybean and potato, whereas that of stems was high in all the crops. The amount of cell wall components in leaves and stems decreased during maturation only in soybean and potato.