Strikingly high content of grain protein in solution‐cultured rice

Abstract

A greenhouse experiment was conducted to investigate the nutritional quality of solutioncultured rice. Five rice cultivars, different in grain amylose content and protein content, were grown under 10, 40 and 80 mg l −1 nitrogen levels during the period of July 2003 to October 2003. In comparison to their original seeds, the solution-cultured rice Oryza sativa L grain had strikingly higher protein content across all the cultivars and nitrogen levels, and remarkably lower amylose content in the waxy and low amylose cultivars, which might be due to the sufficiently stable nitrogen supply and well-controlled temperature and humidity. The highest grain protein content was 163.6 g kg −1 in this experiment, which is the highest reported rice grain protein content. The residual nitrogen concentration was greater than 12.39 g kg −1 in the roots, 8.95 g kg −1 in the stems, and 21.97 g kg −1 in the flag leaves across all the cultivars and nitrogen treatments at harvesting. The rice grain had a narrow range of grain carbon content and hydrogen content. The average grain carbon and hydrogen contents for all the rice samples were 42.95 ± 0.15 (n = 60) and 6.81 ± 0.04 g kg −1 (n = 60), respectively. The solution cultured rice grain was characterized with lower carbon-nitrogen mole ratio and lower hydrogen-nitrogen mole ratio, which could be mainly attributed to the increased protein content. The response of plant nitrogen, grain protein and amylose concentration to the supplemental nitrogen level varied with the cultivars. The results in this study suggested that solution culture technology could improve the production potential of rice.