Effects Of Drought Stress On The Growth And Physiological Characteristics Of Sorbus Alnifolia

In this paper, Sorbus alnifolia as the test material, the potted weighing control watersimulation of soil drought stress, The relative soil moistures for the different treatments werecontrolled at75%-80%(control),60%-65%(light stress),45%-50%(moderate stress),30%-35%(heavy stress).The purpose is to research drought stress launching Sorbus alnifoliagrowth and physiological characteristics of the variation, aimed at understanding Sorbus alnifoliaability to adapt to drought stress and adaptation mechanisms. To provide a scientific basis for theintroduction of domesticated of Sorbus alnifolia, the main results of the paper are as follows:1. With the degree aggravating of drought, seedling height and to stem of Sorbus alnifoliaare reduced, shows that drought inhibits Sorbus alnifolia’s elongation and enlargement; Sorbusalnifolia’s biomass above ground and underground are reduced, but the biomass above grounddecreased more than underground part, lead root/shoot ratio to elevated and biomass allocation toincline to the direction for the root absorbing water, but under severe drought, Sorbus alnifolia’sroot is severely damaged, the biomass under ground decreases more than part of on the ground,root/shoot ratio decreases.2. With the degree aggravating of drought, Sorbus alnifolia’s Blade thickness and thethickness of palisade tissue are gradually increased, spongy tissue thickness decreases, ratio ofpalisade tissue and spongy tissue increased gradually. These change characteristics helps theCO2and other gases from substomatic chamber entering to the photosynthesis place, but also canimprove Sorbus alnifolia’s water-using efficiency and light energy utilization.3. Under drought, Sorbus alnifolia’s leaf photosynthesis is significantly affected. With thedegree aggravating of drought, Sorbus alnifolia leaf stomatal conductance decreased, netphotosynthetic rate, transpiration rate also decreases, but the intercellular CO2concentrationincreased; Fo, Fm, Fv/Fo, Fv/Fm, Φ PSⅡ andqP of Sorbus alnifolia are falling. It shows thatdrought inhibits the photochemical activity of PSⅡ. NPQ significantly increases, indicates thatSorbus alnifolia’s energy dissipation in the form of heat energy and chemical quenchingincreases, avoiding excess light energy damage of photosynthetic mechanism, but under theheavy drought NPQ declines.4. Drought induced Sorbus alnifolia to produce reactive oxygen species, aggravatemembrane lipid peroxide, significantly increase the relative conductivity and MDA content.Under Drought, the variation trend of Sorbus alnifolia’s leaf SOD and POD activity is Roughlythe same. Under mild stress, SOD and POD activity are rising, Can effectively remove reactiveoxygen species in the body, Maintain normal metabolism of cell functions; But under themoderate and severe drought, with the extension of drought time, SOD and POD activity firstrise after decline. It indicates that active oxygen removal ability of Sorbus alnifolia is limited, shortage of water for a long time leads to generate and remove free radicals in cells and break thebalance, damage protective enzyme synthesis, SOD and POD activity decrease.Comprehensive analysis shows that Sorbus alnifolia in mild stress and moderate stress hascertain drought resistance, but by changing the leaf morphology and biomass allocation, closedporosity, increase the heat dissipation and improve the activity of protective enzyme and otherways to control damage within a certain range. However, severe stress on Sorbus alnifoliadamage beyond its tolerance range, seriously affecting the growth and development of Sorbusalnifolia.