Effects of Water Stress on Root/Shoot Relation and Grain Yield in Winter Wheat

The effects of treatments of different soil moisture and duration on root/shoot relation and the grain yield in winter wheat were studied by the potted experiment of cultivars BeiNong 10 in greenhouse at the scientific experimental areas of China Agricultural University in 2000. The dry weights of root and shoot for every pot were measured. Samples were taken once every 7 days and 18 sample plants were taken every time. In the end, all organs and yields were measured after harvest. According to the experimental data, and based on the differences during the growth and development of winter wheat before and after rewatering, the root/shoot relation and the responses of the yield to water stress were analyzed. The results indicated that there was a exponential decline in root∶shoot ratio of winter wheat with the increase in plant growth. The decrease in root∶shoot ratio came from an allometric growth between root and shoot, which could be expressed by the following equation: y=a+bx Where y is the natural logarithm of the root dry weight, x is the natural logarithm of the shoot dry weight, a is the intercept and b is the linear regression coefficient. The allometric growth effect of root and shoot was distinct under water stress condition(value of b diminished), but it became not so obvious often the recovery of watering (value of b increased), and the growth of root and shoot was harmonious. Water stress had a positive effect on the plant spike number, and the negative effects on the grain number per spike, 1 000-grain weight, grain yield and water use efficiency. The treatments rewatered at the heading stage after moderate water stress from the jointing stage to the booting stage had the best effects on grain yield which was up to 62% of the CK grown under 80% of soil relative moisture at whole growth stage.