| Using four provenances ( from Bushan ML , Funiushan Mt., the north slope of Qinling Mt. and lluanglong Mt.) of Quercus variabilis as materials, this paper mainly deals with the drought-resistant characters and mechanism of four provenances of Quercus variabilis from the aspects of water physiological ecology, photosynthesis, and protection enzyme system unti-oxidation under field experiment and potted experiment. On the basis of the study on the growth and physiological characteristics, index system on comprehensive judgment of drought-resistance ability of the provenances was suggested and the drought resistance ability of the provenances were judged comprehensively. The main results were as follow: 1.The differences of drought-resistance to water stress of four provenances of Quercus var iabilis mainly due to the result of their long-term adaptation to the environment of their original inhabit. There were stable genetic features in morphological character, physiology and ecology, so it is significantly important to evaluate later-generation. 2.The drought-resistance mechanisms of four provenances were deferent. Under drought stress, provenance 4 has the high specific leaf dry weight, strong ability of leaf water holding, low transpiration ; thick and hard cell wall, high water-maintenance, strong ability of anti-oxidation; under sever drought stress, it has the characters of low productivity and high water use efficiency; provenance 1's water potential, cellular elasticity, drought-resistance productivity and water use efficiency dropped dramatically, And it closed its stomas early to minimize the loss of water; its ability of cleanup of protection enzyme system lost the balance too soon, leading to the rapidly accumulation of the HA. and high electrolyte leakage. Provenance 3 has the characters of low transpiration, high root/shoot biomass ratio, high turgor maintaining and osmotic adjustment; its ability of cleanup of protection enzyme system is solely inferior to provenance 4 and it has stronger potential drought-resistance; under sever drought stress,it closed its stomas later to maintain photosynthesis rate, and still can accumulate dry materials to some degreed, provenance 2 has low water potential and water-maintains, normal ability of leaf water holding, its ability of adaptation to water stress and drought-resistance productivity was inferior to provenance 3 but stronger than those of provenance 1. the relationship between predawn water potential of four provenances of Quercus variabilis and soil water content indicated the water stress critical numerical value of provenance 1 is 20%, provenance 2 and provenance 3 are 18% , provenance 4 is 17%. the differences above were the main causes of their different response to water stress and growth status.3. Water parameters and drought-tolerance of four provenances have a seasonal change, the reasons of this changes can be found from physiology and structure during the course of the growth and development of trees. During the period of leaves expanding, these Water parameters reflect their ability of drought-tolerance is weaker, while it happen to lower soil water content, so this period can be called the "ecological weak time" .4. The indices adaptability to drought and of productivity to drought were analyzed. The leaf water-losing rate, photosynthesis, transpiration, water use efficiency and protection enzyme system anti-oxidation and the ability of osmotic adjustment were suggested to be used as comprehensive judgment indexes in drought-resistance provenances selection. Provenance 2 and provenance 3 have a better ability of water adaptability and drought-resistance productivity, Provenance 1 has a faster speed of growth under the normal water condition, but its ability to adapt water stress is weaker, Provenance 4 has the strongest ability of drought-resistance, but it has a normal speed of growth. The principle of suitable trees for suitable areas should be considered in the plantation of Quercus variabilis. |
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