遮荫和环剥对荔枝枝梢生长和光合生理的影响

 以12年生‘黑叶’荔枝（Litchi chinensis Sonn.‘Heiye’）为研究材料，进行遮荫、环剥及遮荫 + 环剥处理，观测这些处理对新梢生长，以及叶片净光合速率、叶片光系统Ⅱ（PSⅡ）最大光量子效率（F_v/F_m）和淀粉含量的影响。结果表明：遮荫处理和环剥处理均能显著抑制枝梢生长，降低叶片的净光合速率，但两种处理抑制光合作用的机制各异。其中，环剥处理导致叶绿素含量降低，产生永久性光抑制，显示光系统Ⅱ（PSⅡ）受到破坏，因此，环剥处理导致光合作用的降低与光反应系统的破坏有关；遮荫下叶片最大光化学效率F_v/F_m维持正常，淀粉含量降低，但即使在相同的人工光源下，光合作用速率同样低于对照，可能主要与暗反应系统活性减弱有关；而遮荫可显著缓解环剥对光反应系统的破坏效应。

Effects of Shading and Girdling on Shoot Growth and Photosynthesis in Litchi

In this study，adaptability of litchi to shading as well as the interaction effects of girdling and shading were examined using 12-year-old‘Heiye’litchi（Litchi chinensis Sonn.‘Heiye’）trees. Within the same tree，shoots were treated with girdling，shading and their combination with ungirdled and exposed shoots as the control. Shoot length，leaf gas exchange and chlorophyll fluorescence were measured at determined dates after the treatments. The results showed that the shoot growth and leaf photosynthesis were significantly inhibited by both shading and girdling treatments，while the mechanisms of photosynthesis inhibition of these two treatments seemed different. Girdling treatment significantly lowered leaf chlorophyll content as well as photosynthetic rate with the occurrence of chronic photoinhibition，an indicator of photosystemⅡ（PSⅡ）damage. In shading treatment，F_v/F_m maintained normal but shaded leaves had a lower photosynthetic rate measured even with the same artificial light compared with the control. The reduction of photosynthesis was therefore chiefly due to the impairment of dark reaction. Interestingly，shading significantly alleviated damage on light reaction system caused by girdling.