Abstract: A pot experiment was conducted under water stressed and adequate water-supplied conditions with two genetype varieties (Shandan9 and Shandan911) to study the effects of nitrogen, potassium and glycinebetaine on their dry matter and grain yields as well as water use efficiency at different stages for revealing the function of these factors in increase of plant resistance to drought or dryness. Results showed that with water stress, dry matter and grain yields were significantly reduced. However, the response of the two varieties to the stress was different: Shandan9 was higher in dry matter and grain yields, and therefore could be regarded as a drought-resistant variety while Shandan911 was not so. Application of nitrogen, potassium and glycinebetaine raised dry matter and grain yields to different levels, and thus alleviated the water stress and increased water use efficiency. The effects were higher on Shandan911 than on Shandan9. Under water-stressed conditions, application of N fertilizer, either at low rate or at high rate, significantly increased dry matter, grain yields and water use efficiency, and significant difference between N rates was found for Shandan911, but no such effect for Shandan9. However, with adequate water supply, the effects of N fertilization were obviously decreased, showing that in addition to supplying nutrient, it has functions in increasing drought-resistance of a crop. Potassium and glycinebetaine exhibited more obvious function in increase of dry matter and grain yields as well as water use efficiency under water stressed conditions while such effects were obviously declined, and even vanished, with adequate water supply, indicating the important contribution of these factors in increase of drought-resistance ability of a crop.

Key words: Nitrogen, Potassium, Glycinebetaine, Water stress, Summer maize