The Photosynthetic Adaptation To Drought And Recovery Mechanism Of Geographical Substitute Caragana Species

Geographical equivalent Caragana species from different rainfall distribution area were chosen to carry on pot-cultured experiment, This study is related to the Photosynthetic Characteristics of gradual drought stress, and dynamic recovery under different degrees drought of Caragana species, this find will help us to understand the photosynthesis adaptation mechanism of Geographical equivalent Caragana species and provide a theoretical basis for the geographical substitute distribution mode which was plant formed. The main conclusions are as follows:1.Under drought conditions, the photosynthesis(Pn), stomatal conductance(Cond)and transpiration rate(Tr) of Caragana declined with LWP decreased.The Pn, Cond,Tr of Caragana of arid and semi-arid area decreased 50% when the LWP is relatively high, the Pn, Cond, Tr of Caragana of moist and semi-moist area decreased 50%when the LWP is relatively low. The results showed that the stomatal closure of the Caragana of arid and semi-arid area was sensitive to the decrease of leaf water potential in order to reduce the transpiration water consumption.2. Re-watering after drought to LWP to-2.0 MPa,-4.0 MPa,-6.0 MPa, it is found that the time of LWP, Pn and Cond restored to the level of control group increased with the aggravation of drought stress.3. Comparison of Caragana species, it is found that the LWP, Pn, Cond of the Caragana from arid, semi-arid area recovered faster then the LWP, PN, Cond of the Caragana from humid, semi-humid area after re-watering. Studies have confirmed that recovery capability of Caragana from arid and semi-arid area are better than semi-humid and humid region species. The study showed that the recovery ability of plant is the key factor to determine its distribution along the gradient of precipitation.4. Comparison of photosynthetic characteristics of 7 kinds of Caragana showed that: the diurnal variation of Caragana from arid area showed a double peak pattern,and the net photosynthetic rate and diurnal photosynthetic accumulation value were relatively higher than others; at noon, the Cond of of Caragana from arid area decreased quicker, the difference of stomatal conductance between the semi-arid andsemi-humid area was not significant. Compared to semi-arid and semi humid area distribution, arid area distribution has stronger ability of carbon assimilation, the stomata to environmental changes is more sensitive, these adaptive physiological characteristics are beneficial to the survival of plants in high temperature and drought environment.