Rice varietal differences in biochemical composition and chloroplast ultrastructure as affected by nitrogen.
1992
Laza M.R.C. | Bergman B. | Vergara B.S.
The biochemical composition and chloroplast ultrastructure as affected by nitrogen were examined in four rice (Oryza sativa L.) cultivars grown in controlled conditions. This is to explore the possible reason for the high photosynthetic ability of IR8 as compared to other cultivars. Among the cultivars tested, IR8 was most responsive to increasing nitrogen having the significantly highest shoot dry weight and protein content. Total chlorophyll and protein contents varied with cultivars and nitrogen level but chlorophyll a/b ratio remained constant. At the ultrastructural level, chloroplast at high nitrogen, had from one to two times as many grana as the nitrogen deficient chloroplasts. Nitrogen deficiency reduced the size of the chloroplast, grana stroma lamellae and had less and poorly-stacked grana. Increasing the nitrogen level above the normal (120 ppm) did not markedly affect chloroplast size of all cultivars except in IR8 which has the largest chloroplast. A reduction in number of starch grains was observed in IR8 but more were present in IR36 under nitrogen deficiency. Size of starch grains was not affected by nitrogen and did not differ among cultivars. The high photosynthetic ability of IR8 may be related to its ultrastructural order. These traits could be tapped and incorporated to improve the photosynthetic ability of a cultivar which may further improve yield potential.
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