Study On Drought-Tolerance Of Precious Tree Acrocarpus Fraxinifolius

In their half year, Acrocarpus fraxinifolius seedlings that were cultivated in light media-container and had a similar growing intendance were selected to examine to the regular of physiological changes under drought-stress environment. The drought-stress test was begin when all seedlings were grown normally with the purpose to test their tolerance of drought-stress under different water status. Several physiological and increment indices including seedling height and ground diameter, Chlorophyll, free-proline, soluble sugar, soluble protein and membrane permeability in leaf, and the water content in root、stem and leaf were measured. Even the change of water in soil was also tested at the same time. It was hoped that such a test may provide theoretical basis for afforestation in arid regions, or for areas with plenty of water but uneven distribution. The main results were showed as follow:(1) Soil moisture of the containers was gradually decreased and the increment of the seedling height and ground diameter was also showed a similar intendance when water provision was stopped. The seedlings were subjected to negative influence which can be seen for appearance when in their11-16th stressing days. This could be taken as a relative evidence for the requirement ofAcrocarpus fraxinifolius seedlings need for soil water.(2) The content of moisture in leaf, stem and in root of the seedlings became less and less as stressing time went by. And the ranges of water content in different organs were leaf>stem> root. The part outside of soil showed a sensitive reaction to the change of soil water content. That is to say, the leaf of Acrocarpus fraxinifolius seedlings could be a good index that indirectly reflects the water stress of external environment.(3) The chlorophyll and soluble sugar were gradually descended and the membrane permeability, soluble protein and free-proline were significantly increased in the11-16th days, which may stand for the water stress had begin. In the17-21th days, however, all the physiological indicators were sharply decreased with the exception of membrane permeability which was increased to74.33%in really short time. This study showed that the suitable water content for Acrocarpus fraxinifolius seedlings was20%-39%.