摘要
以浑善达克沙地优势树种榆树(Ulmus pumila)幼苗为研究对象,在半控制试验中设置4个地下水位梯度(U1、U2、U3和U4,地下水位分别为距离土壤表面1、2、3和4m)研究了不同地下水位处理对榆树光合特征及抗逆性的影响。结果表明:1)随着地下水位下降,榆树对强、弱光的利用能力下降,最大光合能力降低。随着地下水位的下降,榆树叶片光饱和点、表观量子效率及暗呼吸速率均显著下降(p<0.05),U1最大净光合速率可达(10.81±0.28)μmol·m–2·s–1,而U4最大净光合速率降至(8.98±0.08)μmol·m–2·s–1,下降了16.9%;2)地下水位下降使榆树的光能转化效率下降。与U1相比,U2、U3和U4的Rubisco最大羧化效率、光呼吸速率、最大电子传递效率和磷酸丙糖利用率均显著下降(p<0.05),而CO2补偿点显著升高(p<0.05);3)地下水位越低,榆树受到的胁迫越严重。U2、U3和U4的可溶性糖及脯氨酸含量较之U1均显著升高(p<0.05)。因此,地下水位下降会显著降低浑善达克沙地榆树的光合性能,造成干旱胁迫。在实践中应加强地下水管理,这对浑善达克沙地稀树疏林生态系统的可持续发展具有重要意义。
Aims Ulmuspumila, a widespread tree in the semiarid ecosystems of northern China, forms sparse woodlands in Hunshandake Sandy Land. However, the population of U. pumila has been declining in recent years because of a lowered water table, mainly caused by increased human water consumption. Our objective was to clarify the relationships between tree ecophysiological activity and the water table in order to provide information for protection of the species. Methods Saplings of U. pumila were planted in pots with simulated water tables at 1, 2, 3 and 4 m depth （U1, U2, U3 and U4, respectively）. The impacts of water tables on the photosynthetic characteristics and stress tolerence of U. pumila were determined by analyzing photosynthetic light and CO2 curves, pigments, predawn water potential, soluble sugar and proline. Important findings Both the utilization efficiency of strong and weak light by U. pumila and the maximum photosynthetic rate decreased with lowered water table. Compared to U1, the light saturation point, apparent quantum yield and dark respiration rate of U2, U3 and U4 were significantly decreased successively （p 〈 0.05）. The maximum net photosynthetic rate of U4 （（8.98 ± 0.08） μmol·m-2·s-1） was reduced by 16.9% compared to U1 （（10.81 ± 0.28）μmol·m-2·s-1）. Light energy conversion efficiency of U. pumila also declined with lowered water table. Compared to U1, the photorespiratory rate, maximum RuBP saturated rate of carboxylation, maximum rate of electron transport and rate of triose-phosphate utilization decreased （p 〈 0.05） and CO2 compensation point increased in the order of U2 〈 U3 〈 U4 （p 〈 0.05）. The soluble sugar and proline contents significantly increased （p 〈 0.05） with lowered water table, i.e. U1 〈 U2 〈 U3 〈 U4, indicating that the lowered water table induced the greater stress. Therefore, groundwater decline resulted in drought stress and down-graded photosynthetic ability. This implies that the decrease in U. pumila population might be caused by the lowered water table and that maintaining proper underground water table in Hunshandake Sandy Land is helpful to the sustainability of the sparse woodland ecosystem.
出处
《植物生态学报》
CAS
CSCD
北大核心
2012年第3期177-186,共10页
Chinese Journal of Plant Ecology
基金
国家林业局948项目(2008-4-27)
中国科学院战略性先导科技专项(XDA05070102)
中国博士后科学基金(20100480214)资助
关键词
干旱
CO2响应曲线
渗透调节物质
光响应曲线
地下水位
arid, CO2 response curve, osmotic adjustment substance, photosynthetic-light response curve, water table
