Study On Drought Tolerance Diversity And Physiological Characteristics Of Different Maize Varieties

Maize is the second largest crop after rice with food, feeding value and a variety of industrial use, and occupies an important position in the national economy. Maize needs much water and has poor drought tolerance during the whole growth process. The crop area of maize is 2700 million ha.in our country, and 40 percents of which were under drought stress every year. Drought leads yield reduced 20% ~30%, which has been an important limiting fator. As the drought intensifying, drought-resistant maize varieties will be more and more important in agricultural production. An artificial potted experiment was used in this research. A drought-resistant and a non-drought-resistant maize variety were selected from 23 varieties. We researched drought-tolerant physiological basis, root characteristics, carbon and nitrogen metabolism, yield and quality. The main results are as follows.1. There was an obvious difference in drought-tolerant of different maize varieties.23 varieties were clustered to 4 categories. The first included ND-95 and JH582, both of them were non-drought-resistant maize variety. The second kind included JY-11, BH315, F524, ZX584, ZD-958, LY2037, JK-308, HY-18, F521, JD-28 and ZD-828. The third included nine varieties, NK733, ND-86, ND-108, ZD-28, BF7516, JK-25, L699, JK-301, XY-355. The last included only one variety JK-628, which was a drought-tolerant maize variety.2. The physiological characteristics of different drought-tolerant maize varieties under drought stress.Drought stress led photosynthetic rate reduced in maize, and the degree of drought-tolerant maize reduced less than non-drought-tolerant maize. Drought led to SOD, POD and CAT activity decreased in maize leaves, with the degree of drought-tolerant maize reduced less than non-drought-tolerant maize.MDA content of leaves increased under drought stress, and the amplitude gradually increasing as promoting growth. The increased degree of drought-tolerant maize was much lower than that of drought-tolerant maize. Drought led to lower soluble protein content in leaves, and degree of reduced was less in drought-resistant maize than non- drought-resistant.3. The root characteristics of different drought-tolerant varieties.Drought-tolerant maize had larger root system. Although root growth was restraited under drought stress, root dry weight of drought-tolerant maize was lager than non-drought-tolerant. Drought-resistant maize had a high root activity and kept it under drought stress. Drought reduced POD and CAT activity. Root SOD activity was higher in prophase and lower in anaphase of maize, and the time of SOD activity beginning to lower was later in drought-resistant maize than in non-drought-tolerant. The root SOD activity of JK-628 was lower than ND-95. But root soluble protein was higher than it.4. Accumulation, transit and distribution of dry matter and nitrogen in maize.Drought stress led to dry matter accumulation of maize significantly reduced. The transfer rate of dry matter was reduced from organ to grain. Drought-tolerant maize varieties had a lower reduced amount than non-drought-tolerant under drought stress. The reduced amount of dry matter from organ to grain was lower than non-drought-tolerant maize variety. Drought made NHI fall, and the reduced degree was lower in drought-tolerant than non-drought-tolerant maize variety. The efficiency of nitrogen fertilizer reduced obviously under drought stress. The reduced degree of NFE was low in drought-resistant maize variety and high in non-drought-tolerant maize variety.5. The effect of drought on yield and quality in different maize varieties.In the moderate drought stress conditions, kernel number, grain yield and weight per 1000 kernel were significantly decreased in JK-628 and ND-95. The kernel number, grain yield and weight per 1000 kernel were reduced22.73%, 0.87% and 33.7% respectly in JK-628 compared to the control, while 50.93%, 17.46% and 62.3% respectly in ND-95 compared to the control. Under drought stress, ear length, ear diameter, ear rows and row kernel number were significantly reduced, and bald length significantly increased. The total starch content and fat content were decreased; crude protein content and soluble sugar content were increased.