Studies On Whole Plant Drought Resistance Of Three Ulmus Tree Species In Karst Region

According to the viewpoint of whole plant drought resistance, the drought resistance at seeds germination ,seedlings and young trees stages of Pteroceltis tatarinowii,Celtis sinensis , Ulmus parvifolia were studied , from morphological anatomy, physiological and biochemical, PV curves parameters and mineral nutrient etc ., by simulating water stress using PEG liquid, gradual drought stress, repeated cycles of dehydtation-rehydration and reciprocal action of temperature ,humidity and soil water . The main results as follows: The drought resistance behavior , adaptive , methods ,ways, strategies to water stress of these trees were various in different stages of life cycles. The drought resistance of seeds were mainly displayed in both the physiology and morphology characters, and the strategies of drought resistance including the reproductive allocation ,adjusting growing and developing stages periods and germination drought resistance, which covers three adaptation types : drought escape,drought avoidance and drought resistance. The drought resistance of seedlings and young trees were displayed in morphological anatomy, physiological and biochemical and PV curves parameters etc. , and all the parameters contribute to drought resistance , but the effects changing with time. The adaptive strategies of seedlings and young trees to water stress including the reparation ,compensation ,resource reallocation and growth tediousness ,and two adaptation types drought avoidance and drought resistance were formed. The effects of water stress of different types and degrees on physiology, biochemistry and growth of the seedlings were only different in degree, but no difference in essence. The heavier water stress , more dry cycles and heavier reciprocal action among temperature ,humidity and soil water, the more effects on physiology , biochemistry and growth of seedlings were played, and the more difficult to restore after re-watering. The common adaptive traits to water stress of seedlings at different growth stages could be summarized as following:(1) the homogeneity in response and adaptation to water stress and the no-linear in indexes change; (2) the heterogeneity and no-determinacy in time of water stress effect;(3) the variable on adaptation to water stress and the controllable on drought resistance of seedlings;(4) the limitation on proline osmotic adjust and protective enzyme action ;(5) the diversity on adaptive strategies and generality on over-compensation phenomenon;(6) diversity on adaptive ways , consistency on adaptive direction and holism on plant drought resistance. The germination of seeds and drought resistance of seedlings in water stress were improved by soaking seeds and culturing seedlings using different concentration Ca2+ liquid . From the results of studies, the whole plant drought resistance was explained in the paper . The theoretical basis , intension , adjust mechanism , causes of formation and adaptive strategies of whole plant drought resistance were analysed , and the evaluating principle and standard of drought resistance ,indexes screening criteria of drought resistance and evaluating methods to whole plant drought resistance were also explored in the paper. As a sample ,the whole plant drought resistance of Pteroceltis tatarinowi,, Celtis sinensis and Ulmus parvifolia were evaluated synthetically.