Study On Physiological Characteristics Of Desert Plant Reaumuria Soongorica To Simulated Elevated CO₂ Concentration And Precipitation Regimes

Elevated CO₂ and changing precipitation cause tremendious effect on plant,therefore,the study on effect of elevated CO₂ and changing precipitation on physiological characteristics of Reaumuria soongorica has been of increasing interest these days.OTCs were used to investigate the effects of the elevated CO₂ concentration?350,550 and 700 ?mol·mol–1?and changing precipitation?increased by 30%,increased by 15%,unchanged,reduced by 15%,and reduced by 30%?on growth?photosynthetic parameters?antioxidant enzyme and osmotic adjustments of 2-year-old R.songorica,in order to revel the responses and adaptation mechanisms of R.songorica to the elevated CO₂ concentration and changing precipitation,and it can provide a preliminary theoretical basis and scientific support for response to global climate change predition of desert ecosystem.The results showed as follow:1?Plant height,above-ground biomass and total biomass of R.songorica increase with precipitation,elevated CO₂ concentration promotes the incresse of plant height,above-ground biomass and total biomass of R.songorica under all rainfull condition,and the most significant effect is under 15% increase in precipitation and 700?mol·mol-1 CO₂,but elevated CO₂ concentration did not alleviate the negative impact of drought caused by decreased precipitation on R.songorica.The root biomass of R.songorica increase under any rainfull condition,and rainfull increase can promote root development of Reaumuria soongorica than rainfull drought adaptive regulation,elevated CO₂ concentration can promote this effect,but long elevated CO₂ concentration can produce domestication of R.songorica.2?Leaf net photosynthetic rate?Pn??transpiration rate?Tr??stomatal conductance?Gs?and intercellular CO₂ concentration?Ci?increase with the increase precipitation.With increased CO₂ concentration,net photosynthetic rate of R.soongorica increased obviously,the photosynthetic capacity of R.soongorica had a wide adaptability to precipitation under short elevated CO₂,but photosynthetic capacity of R.soongorica decreased under long elevated CO₂ and photosynthetic acclimation occurred during August.The variation tendency of Ci is accordance with the photosynthetic capacity.Transpiration rate and stomatal conductance decreased with elevated CO₂,but the results were opposite with increased precipitation because of the compensation.Water use efficiency increased significantly with increased CO₂ concentration,especially under 30% decreased in precipitation treatment,but this reaction was smaller under long elevated CO₂ than under short elevated CO₂.3?With rainfull increase,the content of chla?chlb?chl?a+b?and Fm?Fv/F_o?Fv/Fm increased,all reached the maximum when 30% increase in precipitation;chla/b and F_o are on the contrast,all reached the maximum when 30% decrease in precipitation.Elevated CO₂ obviously increased the content of chla?chlb?chl?a+b?and F_o of R.songorica,but chla/b?Fm?Fv/F_o?Fv/Fm decreased,the effect improved under rainfull increase.But long elevated CO₂ concentration desroy the chlorophyll optical system? structure of R.songorica,resulting in a decline of photosynthetic capacity and light acclimation.4?With rainfull increase,antioxidant enzyme and MDA decreased,but osmotic adjustment increase under any precipitation,the change range under decrease precipitation is bigger than increase.With elevated CO₂,antioxidant enzyme,osmotic adjustment of R.songorica increased,and acclimation occurred during August;MDA decreased.Therefore,elevated CO₂ concentration seems to have ameliorating effect on drought induced oxidative damage.