Drought-Resistance Of Ulmus Pumila And Ligustrum Lucidum Under Different Water And Fertilization Conditions

Rational fertilization not only improves the quality and quantity of crop but also adjusts the water relationship. Significant achievements have been got in improving drought-resistance and yield of crops on the Loess Plateau by rational fertilization. However in forestry, the research of tree drought-resistance has been concentrated in physiological characters and little attention paid to the role of nutrition elements. The research on effects of nitrogen and phosphorus on water relation, photosynthesis, transpiration and organic osmotic substance by rational fertilization can provide a scientific basis for revealing the mechanisms of tree drought-resistance under different water stress. Therefore, an orthogonally designed experiment of three factors (water, nitrogen, phosphorus), each at three levels, was conducted to probe into the effects of fertilizers on drought-resistance of Ulmus pumila L. and Ligustrum lucidum Ait. The water potential, photosynthesis physiology factor, transpiration consumption factors, water parameters and average of diurnal PLC were measured. Range analysis, variance analysis, principal components analysis, and subordinate function analysis were used to analyze the data. The results showed that:1)The effects of fertilizers on water status in the leaves were not significant. With the aggravation of water stress, the bound water content and bound water/free water ratio increased, at the same time, free water content and water potential decreased.2)The effect of water on photosynthesis physiology factor was very significant. There was a close relationship between the Pn and soil water content. Nitrogen was the next factor affecting the photosynthesis. And phosphorus had the least effect. High nitrogen treatment decreased the Pn under normal water condition and middle water stress. But the result was reverse under high water stress. The changes of stomata conductivity and transpiration rate were main causes leading the change of photosynthesis rate.3)The effects of water and fertilization treatment on water parameters were more significant in L. lucidum than in U. pumila. Phosphorus played an important role in the osmotic adjustment of L. lucidum. Similar changes were observed between the consumption water and transpiration under different fertilization treatments. High average day consumption appeared in the treatment with high photosynthesis rate.4)In normal water condition, the susceptibility of embolism of U. pumila was decreased under fertilization treatments while the susceptibility of L. lucidum was increased. In water stress condition, the average of diurnal PLC of U. pumila was increased and the average of diurnal PLC of L. lucidum was decreased after fertilization treatments.5)The principal components analysis indicated that the eigenvectors of print 1 were transpiration. The eigenvectors of print 2 was water factors. Comparison among the drought-resistant abilities of 9 treatments the eigenvectors of print 1 should be as a priority.6)In regard to the subordinate function values of the two kinds of seedlings, different drought-resistant abilities could be found in the same treatment. This was related to the physiological characters of the trees and their susceptibility to nutrition elements. The worst drought-resistance of the two trees occurred in the treatment 2.