干旱胁迫下文冠果光合指标的变化研究

Photosynthetic Indexes Variation of Xanthoceras sorbifolia under Drought Stress

为了探究文冠果在干旱胁迫下的抗旱尺度及光合生理变化,确定适宜的灌水阈值,以保证在节约有限水资源的同时文冠果生长不会受到抑制。在盆栽条件下,设置5个水分梯度,即土壤含水量分别控制在田间最大持水量(46.4%)的80%(T1)、60%(T2)、40%(T3)、20%(T4),以正常灌水为对照(CK)。利用Li-6400光合仪对文冠果叶片光合指标及荧光参数进行测定。结果表明:文冠果随着胁迫时间的延长和干旱梯度的增加,叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、光化学淬灭系数(q P)均降低,其光合作用受到抑制。荧光参数PSⅡ潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)与水分利用效率(WUE)随着水分胁迫加重而下降,表现为T2>T3>T4,其中T1处理由于灌水充盈使光合参数Pn、Gs、胞间CO2浓度(Ci)反而降低。对不同水分处理下文冠果幼苗光合生理指标进行主成分分析,表现的优劣顺序为:CK>T2>T1>T3>T4。文冠果在60%田间持水量的水分灌量(T2处理)下各项光合指标均表现较好,WUE最高。

The aim of this research is to determine the threshold of irrigation so that it can make sure of the normal growth of Xanthoceras sorbifolia at the same time of saving water by exploring photosynthetic physiology changes of X. sorbifolia under drought stress. In this stu d y , through pot experiment, the photo-synthetic indexes and fluorescence parameters of X. sorbifolia were determined by using Li-6400 under 5 water densities. The soil water content was controlled respectively at 80%（T1 ） ,60%（T2） ,40%（T3）, 20%（ T4） of the maximum water holding capacity, with normal irrigation as CK. The result showed that the parameters （ Pn , Tr, Gs , qP ） decreased with the increase of drought stress time and drought gradient, which caused the photosynthesis restrained. The fluorescence parameters （ Fv/Fo, Fv/Fm and WUE） de-creased with the aggravation of water stress and they showed T2 〉 T3 〉T4. However, the photosynthetic parameters （ Pn, Gs, Ci） of T1 decreased because of adequate irrigation. The seedling photosynthetic inde-xes of X. sorbifolia showed CK 〉 T2 〉T1 〉 T3 〉 T4 by PCA（ principle component analysis） under differ-ent water condition. Results indicate that WUE is the highest and all the photosynthetic indexes perform better when field water content is 60% .