Rice Flower Glumes as an Interceptor of Ultraviolet Rays

[摘要] The effect of ultraviolet (uv) ray on rice (Oryza sativa L) kernel during its kernel development was investigated. Upper one-thirds portion of each flower glumes (palea and lemma) on the middle branches of panicles were cut off immeadiately after flowering. Panicles with the cut glumes were then covered with a vinyl film envelope of different light transmittance in uv range. Kernel development in the cut glumes was greatly inhibited by being exposed either to the natural light or to the light of uv range. Relative humidity, however, seemed not to have a great influence on the development of the glume-cut kernels. The inhibition was most outstanding when exposed to short wave uv rays, although it was lessened as exposed to longer wave uv rays. Inhibitory effect of visible light was very slight. Moreover, under dark conditions, kernels in cut glumes developed quite well beyond the untreated kernels and formed a Dahrma doll shape. In terms of kernel characters, uv radiation produced tapered kernels and promoted a browny coloring of kernel as well. Another experiment as to the degree of glume cutting revealed that under dark conditions, the effect of the extent of cutting on the inhibition was rather slight, although they were very conspicuous when exposed to the natural light. Rice flower glumes was found to intercept uv rays almost completely after the last stage of booting. These results indicate that exposure of young kernels to a short wave uv ray strikingly supresses their development and that rice flower glumes may take an important role in protecting their inside kernel through intercepting harmful uv rays. Rice kernels might substantially have an ability to develop beyond the volume of glumes though their development are usually restricted within the volume limit of their glumes.

[学科分类] 农业科学（综合）

[关键词] Deformed kernel;イネ;Flower glumes;花穎;Light interception;奇形米;Rice kernel;紫外線;Rice plant;光遮断;Ultraviolet ray;米粒