遮阴对骆驼刺叶性状和水分生理的影响

以塔克拉玛干沙漠南缘荒漠绿洲过渡带优势种骆驼刺为试验材料,研究正常光照(NL)、中度遮阴(MS)和重度遮阴(SS)3种不同遮阴环境对骆驼刺(Alhagi sparsifoliashap.)叶厚、单叶面积、比叶面积、比叶质量等叶性状参数和相对含水量、水势、失水速率、气孔导度、蒸腾速率以及水分利用效率等水分生理参数的影响。结果显示:随着光照强度的降低,骆驼刺的叶片厚度(LT)、比叶质量(LMA)、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)明显降低,而单叶面积(LA)、比叶面积(SLA)、相对含水量(RWC)、失水速率(RWL)和水势(WP)明显升高;各叶性状参数与水分生理参数之间均有极显著的相关性。说明:骆驼刺在遮阴环境下,其叶性状特征主要通过单叶面积和单叶干物质积累的变化来响应遮阴环境;其水分生理特征主要是牺牲对水分胁迫具有较好抗逆性的水分生理特征并通过气孔调节和更多的水分消耗用于维持一定的光合能力来响应遮阴环境。叶性状与水分生理参数相关性分析表明,遮阴环境下骆驼刺叶性状变化主要通过影响RWL、WP、Tr和WUE进而影响其水分生理特征的变化。因此,建议可利用遮阴措施对极端干旱区荒漠植物骆驼刺进行植被恢复,但其遮光度应设置在70%—80%自然光之间。

The effects of shade on leaf traits and water physiological characteristics in Alhagi sparsifolia

The southern edge of the Taklamakan Desert has a typical inland warm temperate desert climate. It is hot in summer, with little rain and drought; it has abundant light and heat, and strong evaporation; and it has a large water deficit. Desert plants in this region are often subjected to multiple stresses of drought, high temperatures, strong light, and wind and sand. Alhagi sparsifolia Shap. represents an important vegetation community on the southern edge of the Taklamakan Desert. Alhagi sparsifolia Shap. plays an important role in mitigating the effects to wind and sand and in maintaining the fragile ecological environment of the Taklamakan Desert. It is, therefore, important to study the adaptability mechanism and strategy of A. sparsifolia under environmental stress conditions such as extreme light and drought for the restoration of degraded vegetation. Current research indicates that A. sparsifolia is heliophyte. Study of its habitats, however, suggested that-when other conditions were the same-its morphology and physiology changed significantly with increased shading (from 100% natural light to 20% natural light), and the plants rarely appeared when shading increased enough. Therefore, this study assumes that the shading environment will have a significant impact on the morphology and physiological ecology of A. sparsifolia and will affect the distribution and succession of vegetation communities as the degree of shading increases. The objectives of this study were to investigate the effects of shade on the leaf traits and water physiological characteristics in A. sparsifolia on the southern edge of the Taklamakan Desert. We conducted three treatments:natural light (NL), moderate shade (MS) and severe shade (SS). The results showed that increasing shading significantly reduced the leaf thickness (LT), leaf mass per unit area (LMA), net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and water use efficiency (WUE) in A. sparsifolia, while it increased the individual single leaf area (LA), specific LA (SLA), relative water content (RWC), water loss rate (RWL) and water potential (WP). We concluded that A. sparsifolia changed its leaf traits to adjust to shade by changing the single LA and single leaf dry matter accumulation; changed its water physiological characteristics to adjust to shade by attenuating characteristics that have good resistance to water stress; and adjusted its stomatal regulation and water consumption to maintain a certain photosynthetic capacity. Correlation analysis between the leaf traits and water physiological parameters show that the changes in leaf traits in A. sparsifolia in shade mainly influenced the RWL, WP, Tr and WUE, which then influenced the changes in water physiological characteristics. Therefore, this study recommends protecting and repairing A. sparsifolia in extreme arid regions using shading measures; however, the degree of shade should be between 70% and 80% natural light.