Relations between physiological heterosis of root and shoot systems of hybrid rice
1989
Lu, D. (Zhejiang Academy of Agricultural Sciences, Hangzhou (China))
Hybrid rice Shan-You 6 as a late crop out-performed its three parents and conventional cultivars in root growth, N uptake, ability to synthesize amino acids, and root activity. Growth vigor of the root system occurred at seed germination. Heterosis in seed germination is mainly a function of high respiratory rate and diastase activity. Alpha-amylase in the endosperm of the dry seed is the important physiological basis of high diastase activity at early germination, resulting in seedling growth vigor. The hybrid displayed its N uptake vigor in absorption rate per plant. Nutrient uptake and dry matter production are closely related. Free amino acids separated from the bleeding sap of the hybrid included 20 protein amino acids and 11 nonprotein amino acids. The high number of free amino acids shows its distinct heterosis. There are quantitative differences between varieties, but qualitative differences in free amino acids in the exuding sap of intact and clipped plants suggest a nutrition feedback from the aboveground parts to the underground parts. Root activity is low at tillering, increasing gradually to panicle initiation, reaching maximum at booting, then dropping. Mid- and late-growth stage of hybrid root activity could be depressed by N deficiency and promoted by N fertilizer application. Improving aeration at late growth stages gave effects similar to those of N fertilization. Improved aeration may maintain the chlorophyll function of rice leaves better than N application. Early diagnostic indices of heterosis might be diastase activity of seed 1-3 d after soaking and percentage root surface that is actively absorbing at seedling stage. Root activity from booting to milk stage, reduction in root activity, and aging leaf indices might forecast yield.
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