不同温度条件下沙冬青幼树对土壤失水及复水的生理响应过程

Physiological responses of young Ammopiptanthus mongolicus to soil water loss and rehydration under different temperature

沙冬青(Ammopiptanthus mongolicus)是我国西北荒漠区重要的防风固沙造林树种,当地高温、少雨的气候条件常会对其生长产生高温和干旱的双重胁迫,文中以沙冬青幼树为试材,通过人工气候箱调控气温(25℃、32℃、39℃和45℃),采用自然失水的方法(停止浇水0、3、6、9、12d),模拟研究荒漠区定植后的沙冬青幼树对夏季高温和干旱双重胁迫的生理及光合的响应过程,以期为该地区沙冬青定植后的水分管理提供理论依据。结果表明:当气温在25-39℃下,随土壤含水量降至10%,沙冬青叶绿素含量、净光合速率、气孔导度等指标小幅升高;土壤含水量小于6%时,沙冬青幼树叶片含水量、净光合速率、气孔导度和蒸腾速率、水分利用效率等指标明显降低;复水后上述指标均呈现恢复趋势。当气温升至45℃,沙冬青幼树叶片含水量、叶绿素含量、净光合速率、气孔导度、蒸腾速率和水分利用效率随土壤失水逐渐降低;当土壤含水量为6%时,净光合速率、气孔导度、蒸腾速率接近0;复水后上述指标也未见恢复现象。此时,高温、土壤失水或复合胁迫都使沙冬青幼树无法正常生长。当气温从25℃升高至39℃时,沙冬青的生理及光合指标受水分的胁迫较大,然而可通过适当浇水来缓解高温及土壤失水对沙冬青幼树造成的不利影响。

Ammopiptanthus mongolicus is an important afforestation tree for desertification control in desert areas in northwest China.The climatic conditions with high temperature and little rainfall threaten the growth of A.mongolicus with both high temperature and drought stress.In order to provide a theoretical basis for water management in the desert area,the physiological and photosynthetic responses of the young trees of A.mongolicus to the double stress of high temperature and drought in summer were simulated.The results showed that chlorophyll content,net photosynthetic rate and stomatal conductance increased slightly when the temperature was 25-39℃and the soil water content decreased to 10%.When the soil water content was less than 6%,the leaf water content,net photosynthetic rate,stomatal conductance and transpiration rate,water use efficiency and other indexes of young leaves of A.mongolicus decreased significantly.The above indexes showed a recovery trend after rehydration.When the temperature rose to 45℃,the water content,chlorophyll content,net photosynthetic rate,stomatal conductance,transpiration rate and water use efficiency of young leaves of A.mongolicus decreased gradually with soil water loss.When the soil water content is 6%,the net photosynthetic rate,stomatal conductance and transpiration rate are close to 0.The above indexes did not recover after rehydration.At this time,high temperature,soil water loss or combined stress all make the young tree cannot grow normally.When the air temperature increased from 25℃to 39℃,the physiological and photosynthetic indexes of A.mongolicus were greatly stressed by water.However,the adverse effects of high temperature and soil water loss on young trees of A.mongolicus could be alleviated by proper watering.