土壤水分胁迫下沙漠葳的光合生理特征

Photosynthetic Characteristics of Chilopsis linearis under Soil Water Stress

以从美国西部引进的沙生灌木——沙漠葳（Chilopsis linearis）的2年生实生苗为材料,通过盆栽试验于7-9份进行轻度、中度和重度土壤水分胁迫处理并分析其光合生理响应特征.结果显示：（1）60 d中度或重度土壤水分胁迫使沙漠葳的净光合速率（Pn）、水分利用效率（WUE）和光补偿点（LCP）显著降低,暗呼吸速率（DRR）减弱,而气孔导度（Cs）增大,气孔限制值（Ls）变小.（2）Pn日变化在7月份的轻度和中度土壤水分胁迫下表现为双峰曲线,其余月份的胁迫处理均为单峰曲线,同期内各胁迫处理Pn峰值出现的时间基本相同,而且8月份各水分胁迫的Pn值显著高于其它月份;WUE的日变化趋势和Pn日变化相似,而且土壤水分胁迫越严重,其水分利用效率越低;各水分胁迫处理的Pn和Tr光响应拟合曲线均基本呈抛物线形或倒抛物线形.（3）在轻度和中度土壤水分胁迫的初期,Pn降低主要受气孔限制因素的影响,随着胁迫期的延长和胁迫的加重,Pn降低由气孔限制为主逐步转向以非气孔限制为主.研究表明,沙漠葳对干旱胁迫具有一定的适应能力,但长期中度或重度干旱胁迫都会影响沙漠葳的正常生长发育,使其光合生产力大大降低.

Chilopsis linearis introduced from the central-western USA is a kind of desert shrub. The photosynthetic characteristics of potted 2-year-old Chilopsis linearis seedlings were studied under light degree soil water stress,middle degree soil water stress and heavy degree soil water stress from July to September. The results showed that net photosynthetic rate （Pn） ,water use efficiency （WUE） and light compensate point （LCP） of C. linearis decreased markedly with weakened dark respiration rate （DRR）, but stomatal conductance （Cs） augmented and stomatal limit value （Ls） diminished. With the changes of time and months,Pn of C. linearis showed obvious diurnal courses and seasonal courses under three soil moisture conditions. Under light and middle degree soil water stress, variation trend of Pn was the typical ＂flag curves＂ with double peaks in July,but in the other months,it was the single peak curve. Pn of C. linearis in August was higher than that in July and September. With the aggravation of soil water stress,WUE is reduced and its diurnal variation curve was consistent with that of Pn which could be affected by the stomatal limitation factors in the first stage of soil water stress and by the nonstomatal limitation factors in the last stage. All fit curves of Pn and Tr （transpiration rate） generally showed ‘parabola-form＇ and ‘ reverse pa-rabola-form’. It was concluded that this shrub can resist drought stress in a certain extent though its growth and development can be severely effected by the long-term middle or heavy soil water stress which caused the individual photosynthetic productivity of this species to decrease excessively.