Effects Of Elevated CO₂ Concentration And Drought Stress On Water Physio-ecological Characteristics Of Plants

There will have an important impact on forest vegetation with the proportion of CO₂ in the atmosphere is increasing.At the same time,drought stress is influencing plants' growth and development through a series of physiological and biochemical response.In order to discuss the effects of elevated CO₂ concentration and drought stress on water physio-logical of plants,seven species of landscape plants were studied on in the research,including Pinus tabulaeformis Carr.,Platycladus orientalis(L.) Franco., Robinia pseudoacacia L.,Acer truncatum Bunge.,Fraxinus chinesis Roxb.,Euonymus japonicus Thunb. and Syringa oblata Lindl..The research was carried out by the methods of the artificial drought tests and controlled CO₂ concentration gradient(350μmol·mol^-1 and 700μmol·mol^-1).The test results showed that the promotion of elevated CO₂ concentration on net photosynthetic rate increased significantly,with evergreen conifer trees increaseing by an average of 34.3%and broad-leaved trees by 21.0%.Both transpiring rate and stomatal conductance decreased with the CO₂ concentration increasing. The transpiring rate of conifers dropped by an average of 21.5%,and the broad-leaved trees' dropped by 31.8%.Water use efficiency of plants was promoted by elevated CO₂ concentration significantly with conifers increasing by 69.0%and broad-leaved trees by 78.0%.The average daily water consumption, the maximum daily water consumption,the average water consumption rate and the maximum rate of water consumption rate were all decreased observably under drought stress and elevated CO₂ concentration.Elevated CO₂ concentration also made the leaf water potential of Acer truncatum increase by 21.0%at light stress and 15.2%at severe stress significantly.Interaction of elevated CO₂ concentration and drought stress enhanced the chlorophyll fluorescence characteristics of saplings,that was in favor of photosynthesis and accumulation of photosynthate.In conclusion,the beneficial effects of elevated CO₂ concentration on the plants could offset the negative effects of drought stress partly. Interaction of elevated CO₂ concentration and drought stress improve the drought resistance and water use efficiency of plants,which is significant for plants' growth and survival.