Euphratica Shoots And Young Leaf Development, Physiology And Ecology Research

The water resource in E Jina is getting less and less. Drought stress is the most important factor of limiting plant growth and development. Populus euphratica Oliv, one of the most primordial species, is a kind of important hungriness-riverside trees in desert area It is one of the species listed in the first group of rare plants in China. P. euphratica plays an important role in improving the environment due to the strong abilities to adapt to the desert climate in E Jina area.For studying the adaptive mechanism and resisting inverse mechanism of P. euphratica, P. euphratica in Ejina area were selected as experimental material in four different sites, which were in period of dormancy, germination and growth. The experiment was carried out in winter, 2005 and in spring, 2006. The hormones (IAA, ABA, GA₃, ZR) of the buds and leaves were mensured by ELISA. The contents of solubil(?)(?) sugar and starch in different sample of different period were measured by carbolic acid law and anthrone-sulfuric acid law. The following conclusions were made out based on the experiments:1. Morphologic changes of bud and young leaf(1) There were about three kinds of leaf form in P. euphratica, which was lanceolate leaf, intergradation of leaf and broadovate leaf. The branch of the lanceolate was much slender than that of broadovate, and its internode was longer than that of broadovate. The buds of the lanceolate were thinner, while the buds of the broadovate were obesity.2. Changes of hormone in buds and leave(1) The cooperation of various hormones influenced on the growth of P. euphratic, and the equilibrium of different hormones was more important than single hormone. The effect location of each kind of hormone was unequal in different developing period. In different part of blossom bud, the match ratio of various hormone was different.(2) The difference of hormone content was obvious in each part of blossom bud in different period. After dormancy period, the content of hormone in the blossom bud without squama decreased gradually. On the contrary, the content of hormone in bud squama increased gradually. IAA and ZR promoted the growth of blossom bud though the contents of them increased a bit. The change of ABA content in different part of blossom bud was a clear proof that effect location changed in the growth of blossom bud. When bud squama outside accumulated ABA in large amount, growth of bud squama outside almost stoped, but the growth of naked blossom buds began because of the decrease of ABA and the increase of ZR and IAA.(3) The content of ABA in lanceslate dormancy bud was highest. This was related to regulation of ABA in the bud's dormancy. Changes of hormones in the broadovate bud appeared a wide margin fluctuation, which showed that regulation mechanism in lanceslate and broadovate bud was different from each other.3. Changes of saccharide in buds and leave(1) In the four sites of experiment, the content of solubility sugar in both blossom bud and leaf bud was higher than the content of starch. The content of solubility sugar and starch in both buds and leave of P. euphratica lived under different underground water table (UWT) were different. Where the UWT was lower, the content of solubility sugar was higher, while the content of starch was lower. It showed that the content of solubility sugar in P. euphratica was much more correlativity to water condition. The content of starch connected with the bud's growth state, it is relevant to the consumption of nutrient substance in the bud's growth.(2) The content of solubility sugar and starch was also relevant to temperature. During the period of dormancy , the annual average temperature reached to the lowest level. The change of solubility sugar content in buds appeared a wave crest, while the starch content a wave trough.Based on conclusions above, it is clear that the growth and development of P. euphratica were regulated by the cooperation of various hormones. The changes of saccharide in buds and leave of P. euphratica were relevant to temperature andunderground water table (UWT). This study is helpful to find out the mechanisms of adaptation of P. euphratica to dry environment.