Responses of purple rice variety to light intensities and soil zinc application on plant growth, yield and bioactive compounds synthesis

Abstract

Low light intensity restricts rice productivity, however, no deep information is evaluated on purple rice production and its bioactive compound. This study investigated the effects of light intensity on plant growth, yield, and bioactive compounds synthesis during the vegetative (experiment 1) and reproductive (experiment 2) stages of purple rice varieties grown with and without zinc fertilizer application. At the seedling stage in experiment 1, low and intermediate light intensities significantly decreased the total dry weight by 31% and 63%, respectively, compared with the full light intensity. The lower light intensity also decreased the concentrations of seedling total anthocyanin by 81% and total phenol by 36% compared to the full light intensity. At the reproductive stage in experiment 2, shading at early and seed development stages decreased grain yield by 15% compared to the unshaded grains. The concentrations of total anthocyanin and total phenol, DPPH activity, and anthocyanin compounds were increased by shading, while phenolic acid and flavonoid compounds were fluctuated depending on the compound species. Applying soil zinc fertilizer produced no significant improvement in productivity or bioactive compounds but did increase grain zinc concentration by from 6% to 13% compared to zero zinc application. These results will be useful for improving grain yield and quality in purple rice cultivation during the rainy season.