塔里木沙漠公路防护林3种植物光合特性对干旱胁迫的响应

利用Li-6400光合作用系统在沙漠腹地测定分析塔里木沙漠公路防护林植物梭梭(Haloxylon ammodendron)、多枝柽柳(Tamarix ramosissima)和乔木状沙拐枣(Calligonum arborescens)光合特性对干旱胁迫的响应,探讨了水分亏缺对防护林植物光合积累的影响作用。结果显示:沙拐枣的净光合速率、蒸腾速率、水分利用效率、光能利用效率及潜在光合作用能力对水分亏缺最敏感,而柽柳则最不敏感;不同处理下3种植物光合特性变化的差异表明,不同植物对水分亏缺有着不同的响应变化和适应方式;此外,干旱胁迫未提高3种植物的水分利用效率,反而降低了其光能利用效率;C3植物多枝柽柳在干旱高温条件下保持着比C4植物梭梭和沙拐枣更为稳定的光合积累和水分利用效率,说明部分C3植物具备不弱于C4荒漠植物的干旱耐受适应能力;虽然水分亏缺对3种植物的光合作用能力均存在不同程度抑制作用,但未对其光合积累造成不可逆转的影响。可见3种植物都有很强的干旱适应与耐受能力,这种能力表明沙漠公路防护林的灌溉管理还有进一步的节水空间。

Photosynthetic characteristics responses of three plants to drought stress in Tarim Desert Highway shelterbelt

The plants growing at the Tarim Desert Highway shelterbelt has been safe-guarding the highway located in hinterland of Taklimakan Desert, by preventing sand erosion and sand intrusion. Thus, the sustainability of the green belt is vital to the maintenance of the highway. The objective of this study is on the impact of drought stress to the photosynthetic accumulation of shelterbelt plants. LI-6400 portable photosynthesis system was used to measure the photosynthetic characteristics of three plants (Haloxylon ammodendron, Tamarix ramosissima and Calligonum arborescens) under different water conditions. The results showed that: the net photosynthetic rate, transpiration rate, water use efficiency, light use efficiency and potential photosynthesis capacity of C. arborescens are most sensitive to water deficit, while T. ramosissima was the least sensitive among the three species. The differences in photosynthetic responses of these three species to drought dress indicated that the three species have different adaptive mechanisms to water deficit. In addition, under drought stress, water use efficiency of all three species did not improve and their light use efficiency was even reduced. Under drought and high temperature conditions, T. ramosissima, the only C3 species, maintained more stable photosynthetic accumulation and water use efficiency than H. ammodendron and C. arborescens, the two C4 species, which demonstrated that C3 plants also could have high ability of drought resistance than C4 plants under desert conditions. Although water deficit has inhibited, to certain degree, the photosynthesis ability of all three species, it did not have irreversible impact on their photosynthetic accumulation. Therefore, all plants have demonstrated high ability of drought tolerance, and this ability implies that there might still room for water-saving in shelterbelts irrigation.