| The potted 2～4-year-old seedlings of three tree species were tested to study their responsive characteristics to drought stress and shading.The three species include the followings : Arecastrum romanzoffianum var,austral,Trachycarpus fortunei,Livistona chinensis.Gradient water control were taken to research on drought resistance of seedlings; Different shading treatments were taken to control light intensity, researching on the shade tolerance of seedlings. The growth,physiological and biochemical indexes of these seedlings were measured,then based on which evaluation indices system of resistance was established and the resistance of three seedlings were evaluated through subordination function of vague mathematics.the results showed as follows:(1)Under drought stress, three palm seedlings with the more biomass were those growing under soil relative moisture of 80% than in CK (100%). Afterward,the biomass of seedlings appeared a decreasing trend with the decline of content of soil water. The ratio of root to stem and leaf was increasing obviously in soil relative moisture of 40%.The free-water content and the ratio of bound-water to bound free water of leaves of seedlings is more sensitive to drought stress.The free-water content of leaves was decreased gradually with the enhancement of drought stress intensity,but the ratio of bound-water to free-water was increasing gradually with the enhancement of drought stress intensity .The contents of chlorophyll of the seedlings were decreased with the time of drought stress and the decreasing extent of Trachycarpus fortunei was large. The relative conductivity and MDA contents were lower in soil relative moisture of 40%.The free proline contents of three seedlings were increasing obviously under drought stress,but with the increasing of stress time,the free proline content of Arecastrum romanzoffianum var,austral decreasing with the decline of content of soil water.The soluble sugar contents of three seedlings had inconsistent change with the decline of content of soil water,and the soluble protein contents were increased at first and then decreased with the increasing of stress time.(2)Under shading treatments, three palm seedlings with the most biomass is those growing under 40% relative illumination (RI), afterward,the biomass of seedlings appeared a decreasing trend with the decrease of light-intensity. The ratio of root to stem and leaf was decreasing with the decrease of light-intensity. The caloric value of the leaves of the seedlings was significantly reduced under lower light intensity.The chlorophyll contents of three palm seedlings were affected significantly by the different light-intensity and increased under low light .The chlorophyll contents of seedlings were decreasing with the decrease of light-intensity and with the increase of stress time.The and MDA contents had an increasing trend with the decrease of light-intensity,but the relative conductivity was decreased under 1% RI and the decreasing extent of T. fortunei was largest than others , the decreasing extent of A. romanzoffianum var,austral was least.The MDA contents of A. romanzoffianum var,austral and L. chinensis were large under 1% RI and were decreasing significantly with the increase of stress time,it has a opposite trend in T. fortunei. The general trend of the changed of free proline, soluble sugar, soluble protein content was similar.The free proline contents of seedlings were increasing with the decrease of light-intensity.But the free proline contents of T. fortunei. and L. chinensis appeared a decreasing trend with the increase of stress time., it has an opposite trend in A. romanzoffianum var,austral.The soluble sugar contents of three seedlings was decreasing with the decrease of light-intensity.But it appeared a decreasing trend with the increase of stress time.The soluble protein contents was decreasing with the decrease of light-intensity.(3)The free proline what the cumulating rate was quick in T. fortunei. and was one of important adjustable substances and play an important role under drought and shade stress. The soluble protein was one of important adjustable substances.The role wasn't distinct of these osmotic adjustment substance in L. chinensis.(4)The drought and shade tolerance of three palm seedlings were contrasted and compared through subordination function of vague mathematics. The resistant abilities of three palm seedlings were listed in descending order as follows: The drought-tolerance:L.chinensis>T. fortunei.>A.romanzoffianum var,austral. The shade-tolerance: L. chinensis >A. romanzoffianum var,austral. >T. fortunei. |
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