土壤水分含量对Larrea tridentata苗木光合生理特性的影响

为了进一步了解Larrea tridentata对干旱胁迫的响应和适应能力，对其经营管理、栽培措施及水分的高效利用提供理论依据，该文在不同土壤水分含量下,使用Li-6400便携式光合作用测定系统对叶片的光合作用、蒸腾、气孔导度等生理指标进行测定，并测定光响应曲线。结果表明:在供水良好的情况下，L.tridentata的净光合速率与蒸腾速率日变化都呈双峰曲线，有明显的“午休”现象，随着干旱胁迫的加重都变成单峰曲线，日平均值明显降低，特别是蒸腾降到极低水平，反映出苗木具有很强的减少水分损失的能力；随着土壤干旱胁迫的加重，光合作用的变化以气孔调节为主，说明L.tridentata以气孔调节适应干旱的能力很强；L.tridentata光饱和点高，属于强阳性树种，可利用的光强区域很宽；干旱对L.tridentata叶片的光化学过程的影响不是很大，当土壤水势达到-2.415 MPa时，L.tridentata的光合器仍没有受到任何损害；水分亏缺能适当地提高L.tridentata的水分利用效率，说明L.tridentata抵御干旱的能力很强。 

Effects of soil moisture on photosynthetic characteristics of Larrea tridentata seedlings

In order to find out the ability of drought resistance of Larrea tridentata,the authors used Li-6400 portable photosynthesis system to measure the photosynthetic characteristics,transpiration and stomatal conductance of L.tridentata under different soil moisture treatments.The photosynthetic response curves were measured at the same time.The results showed that,the diurnal curves of net photosynthetic rate and transpiration rate were "twin-peaked" under better water conditions,and there was a significant midday depression.Under water stress,the average of net photosynthetic rate and transpiration rate depressed distinctly,especially the transpiration rate fell to the extreme low level.It reflected that the ability of reducing the moisture loss of L.tridentatais was strong.With the increase of water stress,photosynthesis was mainly adjusted by stoma,which showed that the ability of adapting the drought with the adjust of stoma of L.tridentata was strong.Light saturation point of L.tridentatais was high,reflecting that L.tridentata belongs to the masculine tree.Water stress had little influence on leaf's actinic process.Photosynthetic apparatus were not harmed by drought.Water utilization efficiency was raised to some extent with water stress.It showed that the ability of drought resistance of L.tridentata was strong.