黄土丘陵区紫丁香叶片气体交换参数的日变化及光响应

 在半干旱黄土丘陵沟壑区,应用英国PPS公司生产的CIRAS2型光合作用系统,测定不同土壤水分下4年生紫丁香(SyringaoblataLindl.)叶片气体交换参数的日变化和光响应特性。结果表明:丁香光合速率、蒸腾速率、叶片水分利用效率、气孔导度、胞间CO2浓度等气体交换参数,对土壤水分和光合有效辐射的变化,具有明显的阈值响应。有利于丁香光合作用和水分有效利用的适宜土壤质量含水量范围在15%～19.5%之间,土壤相对含水量为58.8%～76.6%;适宜的光合有效辐射强度范围在600～1000μmol/(m2·s)之间。在此土壤质量含水量和光合有效辐射强度范围内,丁香的光合作用和生长过程不会发生较大的水分胁迫和强光胁迫,也不会发生蒸腾速率过高造成的无效蒸腾耗水,因而能获得较高的光合速率和叶片水分利用率。维持丁香正常生理和生长过程所需的最低土壤质量含水量在11.6%(土壤相对含水量为45.7%)左右,相应的最高光合有效辐射强度在800μmol/(m2 ·s)左右,土壤质量含水量降低或光合有效辐射强度升高,会导致严重水分胁迫和。

Diurnal Variations and Response to Light of Gas Exchange Parameters of Clove (Syringa oblata Lindl.) Leaf in Loess Hilly Region

With CIRAS-2 portable photosynthesis system, diurnal variations and response to light of gas exchange parameters of clove (Syringa oblata Lindl.) leaf in four years old were studied under different soil moisture content in the loess hilly region in semi-arid area. The results indicated the Photosynthetic rate(P_n), T_ranspiration rate(T_r), Water Use Efficiency of Leaf(WUE), Stomatal conductance(G_s) and Intercelluar CO₂ concentration (C i) had clear threshold value responses to soil moisture and Photosynthetic Active Radiation(PAR). The fitting range of Mass Water Content(MWC) is 15 0%～19 5%, Relative Water Content(RWC) is between 58 8% and 76 6%, the fitting PAR range is 600～1000μmol photons·m^-2·s^-1. In that range of MWC and PAR, Syringao blata lindl can get higher P_n and WUE, and will not waste water because of high T r, and the Pand WUE will weaken out of those range. The lowest MWC is about 11 6%(RWC is 45 7%), and the corresponding highest PAR is about 800μmol photons·m^-2·s^-1, the falling of MWC or the increasing of PAR will lead to serious aridity stress and high light stress. The results showed that in the hilly-gully region in semi-arid area, Syringa oblata Lindl. should be planted in the ubac rather than in the abret, or be planted under other trees to form mixed forest rather than pure forest, which may has higher productivity and effects.