凡莉莉 张洋洋 张彬君 荣俊冬 陈礼光 施成坤 郑郁善

摘  要：在秋冬旱季用Li-6400便携式光合仪测定木麻黄（Casuarina equisetifolia）林下套种的多年生淡竹（Phyllostachys glauca McClure）的光合特性和环境因子的日变化，并用回归分析研究光合特性对环境因子的响应。结果表明，在秋冬季，淡竹净光合速率（Pn）、蒸腾速率（Tr）曲线均呈“单峰型”，Pn无光合“午休”现象;水分利用效率（WUE）曲线呈“双峰型”。冬季淡竹Pn和WUE值高于秋季，Tr值低，在冬季表现出高光合、高WUE值、低蒸腾适应特征。淡竹冬季平均枝条水势（Ψw）（?8.094 MPa）高于秋季（?15.525 MPa），变化幅度小，表现出较强的水分吸收和减少水分损失能力。淡竹光合性能与温度、水分和光照密切相关，淡竹秋冬季光合日变化和水分利用有差异，其中冬季光合水分生理特性优于秋季。

关键词：沿海沙地;淡竹;秋冬季;光合性能

Abstract： In the current study， the diurnal variation of photosynthetic characteristics and environmental factors under natural light was studied in Phyllostachys glauca McClure intercropped in Casuarina equisetifolia forest by the Li-6400 portable photosynthetic system in autumn and winter. The response of photosynthetic characteristics in relation to environmental factors was analyzed by regression analysis. The results revealed that the net photosynthetic rate （Pn） and transpiration rate （Tr） both had a diurnal change with a single peak appearing in autumn and winter. The curve of Pn exhibited no phenomena of midday depression. Water use efficiency （WUE） presented a “double-peak” type. The values of Pn and WUE in winter were higher as compared to autumn whereas Tr values were lower. It showed the adaptation characteristics of higher photosynthetic rate， high WUE and low transpiration in winter. Average water potential （Ψw） （?8.094 MPa） of branches in winter was higher than those in autumn （?15.525 MPa）， with insignificant variation. It showed a strong ability to absorb and reduce water loss of P. glauca McClure. The photosynthetic capacity of P. glauca McClure was closely related to environmental conditions. P. glauca McClure had different diurnal photosynthetic variation and different water utilization strategy in autumn and winter because of environmental factors such as temperature， water content and photosynthetic active radiation. The photosynthetic capacity in winter was higher than that of autumn.

Keywords： coastal sandy land; Phyllostachys glauca McClure; autumn and winter; photosynthetic characteristics

光合作用是一个动态过程，随环境变化而变化，通过测定净光合速率、蒸腾速率、胞间CO2浓度、光合有效辐射等日变化参数以及叶绿素荧光情况表示其光合特性，可以反映植物对环境的适应性。光合作用、蒸腾作用及水分利用率是植物重要的生态生理参数，对林木栽培及管理具有重要的理论指导意义[1-2]。植物水势是植物水分状况的重要指标之一，可以反映植物受环境水分条件制约的程度[3]。植物水势与环境变化之间的相互关系对研究植物对环境的适应能力提供了科学依据。西伯利亚杨（Populus sibirica）幼苗造林时，在极度干旱环境下水分亏缺显著影响光合特性[4];橄榄树（Olea europaea Linnaeus）对干旱胁迫具有很强耐受性，但植物光合气体参数和水分状态受到干旱胁迫的负面影响[5];在干旱胁迫下，当牛奶子（Elaeagnus umbellata）叶片水势降低到?2.0 MPa时仍然可以保持光合活力[6]。……