浑善达克沙地C3和C4植物对干旱胁迫响应策略

 选取浑善达克沙地C₃植物羊草(Leymus chinensis)和C₄植物虎尾草(Chloris virgata)为研究对象,进行2种干旱胁迫处理,处理1将植物浇至饱和含水量后,使其自然干旱10d,之后复水至饱和含水量;处理2是在处理1的基础上,每天晚上让植物接受自然的大气凝结水.处理期间测定植物的叶片水势、比叶面积、气孔密度、氮含量及生物量等生理生态指标,探讨干旱胁迫及复水后不同光合功能型植物对干旱胁迫响应策略.研究表明,(1) 干旱胁迫显著降低了虎尾草的叶片水势,大气凝结水没有显著改变其叶片凌晨水势,干旱胁迫第10天时羊草叶片凌晨水势值显著降低,大气凝结水使羊草叶片的水势值保持在正常范围之内;(2) 不同干旱胁迫下,植物比叶面积和气孔密度与处理前相比呈下降趋势,但在复水后恢复到处理前水平;(3) 干旱胁迫显著提高了羊草叶片的氮含量,而虎尾草叶片氮水平变化不显著;(4) 干旱胁迫显著提高了羊草的根冠比,而虎尾草的根冠比影响不大,但干旱胁迫则显著提高了虎尾草的果重比.羊草在干旱胁迫下分配较多的生物量到根系,有利于水分的吸收,从而提高了其抗旱性,而虎尾草则分配较多的生物量到种子,使其不断扩大繁殖群体.

Response Strategies of C3 and C4 Plants to Drought Stress in Hunshandake Sandland

It is widely reported that global climate change has affected on the growth and distribution of plants. In order to investigate the response of different photosynthetic functional plants to drought stress, C₃ plants (Leymus chinensis) and C₄ plants (Chloris virgata) are chosen from Hunshandake Sandland to experience drought stresses treatments. One treatment was that the plants were drought naturally for 10 days after a saturant watering; the second treatment was that the plants were drought naturally for 10 days with accepting dew at each night after a saturant watering. Then the hydrological characteristics i.e. leaf water potential at dawn, the specific leaf area, stoma density, nitrogen content, and biomass were compared. And then different strategies in response to drought stresses were discussed. Drought stresses significantly decrease the leaf water potential at dawn (ψ_dawn) of Chloris virgata, while dew does not affect on the value of ψ_dawn of Chloris virgata. Drought stresses significantly lower ψ_dawn of Leymus chinensis at the tenth day after the drought period. Dew significantly affects the ψ_dawn of Leymus chinensis. Drought stresses significantly reduce Specific Leaf Area (SLA) and stomatal density; however, both of them are recovered to the normal level after re-watering. Nitrogen concentrations of Leymus chinensis are significantly increased under drought stresses; meanwhile there are no significant changes for Chloris virgata. Ratio of root and crown is improved for Leymus chinensis under drought stresses,and there is no differences for Chloris virgata. But the drought significantly improves the ratio of fruits and crown for Chloris virgata. The result indicates that more biomass is allocated into the roots for Leymus chinensis under drought stresses. This pattern is benefit for water absorption and improves resistance to the drought. By contrary, more biomass is input to produce seeds for Chloris virgata, which is helpful to expand its population. The results indicate that different strategies for two species are applied to in response to the drought stresses, and C₃ species L. chinensis displays the higher ability to resist drought than that of C₄ species C. virgata.