Changes in Indole-3-acetic acid、Cytokinins and Abscisic acid during Grain Development in Rice ( Oryza sativa L. )

• Main Authors: Hsiao-chu Huang, 黃曉菊
• Other Authors: Huu-Sheng Lur
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/08565620457233296316

碩士 === 國立臺灣大學 === 農藝學研究所 === 87 === Improving rice grain quality has been one of the major objectives for both rice physiologists and breeders. In Taiwan, brewer grains, immature grains, and chalky grains usually account for most of the causes degrading commercial value of milled rice. These grain defects are resulted from heterogeneous development of rice grains within panicles. Thus knowledge of the regulation of rice grain development should benefit out improvement of rice grain quality. The objective of the thesis was to study the roles of plant hormones in grain development, especially the heterogeneous development within a panicle. Two varieties with normal (TK16) and large grain size (Pegonil) were treated with three temperatures during grain development stage. Changes in grain weight, water content, endosperm cell number, endosperm hormone levels including IAA, Z, ZR, and ABA, were determined in better developed (superior) and less developed (inferior) grains within panicles. In superior grains of a panicle, grain weight increased faster and grain water content decreased earlier. Inferior grains had lower weight and higher water content until late development stage. Low temperature related in a decrease in grain weight in both varieties. Cell number, expressed as endosperm nuclearous number, increased faster in large grain varieties (Pegonil), and in grains under high temperature treatment. And high temperature enhanced the accumulation of cell number. Nevertheless, cell number showed similar in both varieties after 12 days after flowering. The result suggested that grain size might be more related to the rate of endosperm cell division, but not the final cell number in rice grains. With regard to hormone levels, high concentration of cytokinin and ABA (per fresh weight bases) appeared near 3 and 6 days after flowering for both varieties. IAA increased around 12 days after flowering. TK16 in general had higher IAA, Z, and ZR concentration than Pegonil. The superior grains accumulated higher IAA concentration, and inferior grains had higher Z and ZR concentrations. Thus IAA and cytokinin concentrations in grain seemed to be not related to the final grain weight, as well as cell number of varieties. In hormone contents (per endosperm bases), both IAA and ABA contents accumulated along with the increase of grains dry weight. The large grain variety in general had higher IAA and ABA content than TK16. A significant amount of IAA and ABA accumulated in endosperm of Pegonil under low temperature treatment. The physiological significance of the accumulation of IAA and ABA in maturating grains remains to be studied. The thesis provides a basic physiological information for the heterogeneous grain growth of panicles. while the integrated rationale for the phenomenon should be studied in consecutive experiments.