Effects Of Soil Moisture Stress On The Growth And Eco-physiology Of Rhus Typhina Seedlings

Using pot culture 1-year-Rhus typhina seedlings as experiment materials and adopting themethod of using different weight of soil to control water content, four different levels of waterstresses were applied to examine the effect of water stress on the growth and physiologycharacteristics of Rhus typhina seedlings. The landscape for the future, the cultivation,application of soil and water conservation and the recovery and reconstruction of damagedecosystems to provide reference. The water stresses belong to the soil moisture of 40-45ï¼…(control-CK), 30-35ï¼…(mild water stress-T1 ),20-25ï¼…(moderate soil moisture stress-T2) and 10-15ï¼…(severe soil moisture stress-T3). The main findings are as follows:(1) Initial part of experiments, improving the soil moisture stress torch leaves the MDAand relative permeability. Rhus typhina significantly increased activity of SOD and POD,anthocyanin and carotenoid antioxidant content. After the experiments, three groups of soilmoisture stress were significantly decreased. Relative permeability of soil in four differentmoisture gradients has no significant difference. In late part of stress, it may be growing in arecession period, MDA and the relative permeability increased, but the increase is notsignificent. At this time, the activity of POD and carotenoid content decreased, but SODactivity began to rise again, therefore they are of smaller degree of damage.(2) T1, T2 and T3 of proline and soluble sugar content during stress were significantlyhigher than that in controls. With the heightened stress level they were rising gradually. Itindicated that Proline osmotic adjustment and soluble sugar played an important role in theinfiltration of mediation, and are important Rhus typhina infiltration adjustment materials.However, protein content has decreased dramatically, the reason may be that it is not anosmotic adjustment material, but converted to the form of amino acid metabolism andosmotic adjustment to participate, because of the increased activity of vivo peptide, bodyprotein synthesis was obstructed, protein degradation increased, leading to contentdecrease.(3) Chlorophyll content in the early and middle stress periods were significantly higherthan increase, which will help enhance the Rhus typhina drought, chl a/b ratios in thesub-soil four moisture stress gradients have no significant difference, Rhus typhina showedtolerance strongly. Chls/Car ratio of greater than 3: 1. can improve the photosyntheticpigment chlorophyll in the relative proportion of photosynthetic. capacity and then increasethe role of stress, in the late period four groups were smaller than 3:1 maybe because ofthe growing recession period of the plant.(4) Under the soil moisture stress, Torch tree seedlings net photosynthetic rate (P_n) with the aggravation of stress level and time was gradually decreased. And stomatal conductance(G_s), and transpiration rate (T_r) and intercellular CO₂ concentration (C_i) also declined,indicated the same trend with the net photosynthetic rate. Due to the greater shifting of Pnthan Tr. Torch trees can more seriously decrease their evaporation rate while decrease theirphotosynthesis rate in order to increase their water use efficiency (WUE), and to adapt to thewater stress condition.(5) There is a significant impact on torch tree seedling growth and biomass allocation oflong-term soil moisture stress. Under soil moisture stress, the torch tree height, basaldiameter, number of branches, leafs per plant and root significantly reduced. Main rootshortened, total biomass decreased. Plant height and number of lateral root of four moisturegradient all reach significant levels. Of three soil moisture stress groups branches, leafs perplant and root length were significantly lower than the control. In mild water stress condition,root branch ratio has no significant difference compared with the control. Moderate and severesoil moisture stress has greater impact on the above ground biomass than on the undergroundpart biomass. Therefore, has higher root branch ratio, in order to raise ability competition.