Positional variations in phytic acid and protein content within a panicle of japonica rice

Six japonica rice cultivars differing in phytic acid and protein content were used to investigate the effect of grain position in the panicle on grain weight, phytic acid and protein content. There were significant differences in grain weight, albumin, globulin, prolamin, glutelin, and total protein content among the grains within a panicle for all six cultivars, but no differences were found for phytic acid content. An effect of grain position between primary rachises on grain weight and protein content was clearly detected, while that among top, middle and bottom rachis showed a greater change, varying with the cultivar. Albumin and globulin contents tended to be lower in the grains on the primary rachis than in those on the secondary rachis, and glutelin and total protein contents showed the opposite trend in the three cultivars with lower protein content. There was no significant correlation between phytic acid and protein content in the different grain positions within a panicle. The accumulation of phytic acid and protein during grain development appears to be independent.