Abstract
Summary The protease activity was studied in the leaves and developing grains of two rice varieties viz. IR8 and Supkheru. The activity, on gram fresh weight basis, was higher in IR8 as compared to Supkheru. The grain activity was higher than the leaves at the initial stages i.e. upto 21st day after flowering and thereafter declined continuously uptil 35th day. The leaf activity increased from the initial stages of flowering until maturity of the grains. The levels of reduced nitrogen, total reduced nitrogen, free amino acids in the leaves and grains of IR8 were significantly higher as compared to Supkheru. The reduced nitrogen level in the vegetative parts declined with the progress of maturity, however, the level in the grains increased sharply from 7th to 35th day. The free amino acid content in the various plant parts was significantly higher in IR8 than the corresponding parts in Supkheru. The level was the highest in the leaf blades at the initial stage of flowering and this declined during the subsequent stages. The free amino acids content in the IR8 grains was 4 to 7 times higher as compared to Supkheru. Incorporation of [U- 14 C]-leucine into the grain proteins of IR8 was also higher as compared to Supkheru. IR8 grains accumulated more protein (%N × 5.95) than the grains of Supkheru at different stages of development. At maturity the protein content of the brown rice of IR8 was 10.41 per cent as compared to 8.33 per cent in Supkheru. These studies showed that higher level of reduced nitrogen, efficient translocation of vegetative nitrogen into developing grains, higher level of free amino acids and higher rate of incorporation of amino acids into grain proteins were some of the important factors for higher protein content in IR8 grains as compared to Supkheru.
Published Version
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