常绿阔叶树种栲树幼苗对不同光环境的光合生理响应

Photo-physiological responses of Castanopsis fargesii seedlings to different light environment in an evergreen broad-leaved forest

常绿阔叶树种栲树是亚热带常绿阔叶林中的优势种之一。对比研究了林下、林窗和旷地3个光环境下栲树幼苗的光合特征参数、比叶质量、叶氮含量及叶解剖结构等,结果表明:林下栲树幼苗的光补偿点和暗呼吸速率低,比叶质量小,表观量子效率和光合氮素利用率高,利用弱光的能力强,在低光环境下保持了较高的光合能力;海绵组织发达且表皮细胞厚,是对凉爽环境的积极响应。在旷地,栲树的最大光合速率明显下降,暗呼吸速率显著升高,单位面积的叶氮含量较高但氮素利用率较低;叶厚度和栅栏组织厚度均增加,栅栏组织/海绵组织厚度比值也升高了,但栅栏组织不如海绵组织发达,不能适应高光环境。栲树幼苗在林窗有较高的光合能力,在林窗中能正常生长和更新。

Castanopsis fargesii, an evergreen broad-leaved tree species, is one of the dominant species in subtropical evergreen broad-leaved forests. This paper presented a comparative study on the photosynthetic parameters, leaf mass per unit area （LMA）, leaf nitrogen content, and leaf anatomical structure of C. fargesii seedlings in an evergreen broad-leaved forest under three natural light environments （understory, gap, and open）. In understory habitat, C. fargesii had lower light compensation point （LCP）, dark respiration rate （Rd ） and LMA, and higher apparent quantum yield （AQY） and photosynthetic nitrogen use efficiency （PNUE）, suggesting that this tree species could take advantage of low light and performed high maximum photosynthetic rate （Pmax）- Moreover, the leaf spongy tissue of C. fargesii was well-developed, and leaf epidermal cells were thicker, demonstrating a positive response to cooler environment. In open habitat, C. fargesii had a marked decrease of Pmax while an obvious increase of Rd. Its leaf nitrogen content per unit area （Na） was higher but PNUE was lower, leaf and palisade tissue became thicker, palisade tissue/spongy tissue ratio increased, but palisade tissue was lesser developed than spongy tissue, indicating the low adaptability to high light environment. In gap habitat, C. fargesii seedlings exhibited greater satisfactory photosynthetic acclimation, being able to have normal growth and regeneration.