Effects Of N, K And Glycinebetaine On Raising Crop Resistance To Drought And The Physiological Mechanism

Nitrogen and potassium, two nutritive elements required by plants in large amounts, are usually deficient in dryland regions. Recent studies showed that in addition to supplying nutrients for plants'growth, the two nutrients could improve drought-resistance ability of plants. Glycinebetaine, a water-soluble alkaloid with three-ammonium type, is an important osmoprotectant regulator in the cytoplasm of plants. Applying glycinebetaine could raise drought-resistance of crops under a water stress condition. Due to frequent occurrences of water stress in dryland areas, determination of the importance of the two nutrients and glycinebetaine to plant drought-resistance is necessary for practical use. Reports of many studies have neglected to distinguish the drought-resistance effect from other functions. Differentiation of their direct drought resistant role from its indirect functions may provide a theoretical basis for an understanding of these substances, and make full use of these materials in agriculture production. To confirm drought-resistance ability of these substance, experiments should be conducted under strict conditions to distinguish nutritional effects from drought-resistance function. Otherwise, a proper conclusion for their drought-resistance is difficult to be obtained due to confusions of their two functions. Two pot experiments and a nutrition solution culture experiment were conducted under water stress and adequate water-supplying conditions with two genetype varieties of maize (Shaandan 9 ,a drought-resistant variety and Shaandan 911, a non-drought-resistant variety) to study plant responses to feed these substances under the two water conditions from biological, physiological , plant growth and crop yield aspects. The main results are as follows:1. Under a water stress condition, dry matter and grain yields of Shandan9 were reduced by 31.9% and 6.8% while thoses of Shandan911 were reduced by 42.4% and 24.4%. Drought index of Shandan9 was 0.93 while that of Shandan911 was 0.76. Therefore Shandan9 could be regarded as a drought-resistant variety while Shandan911 could not be. Application of potassium and glycinebetaine significantly raised dry matter and grain yields, and thus alleviated the water stress and increased water use efficiency. However, with adequate water supply, such significant effects were not obtained, showing their functions in increasing drought-resistance of a crop. Application of N fertilizer, either under water stress or adequate...