4个榆科树种水分参数随季节和年龄的变化规律

The change regularity of water parameters in four Ulmaceae tree species with season and age

采用P-V技术研究了青檀、朴树、榔榆、白榆 4个树种水分参数随季节和年龄的变化过程。结果表明, 4个树种的P-V曲线水分参数随季节和年龄的变化规律一致。随季节变化和母株年龄增长,ψsats、ψtlps 和ε逐渐降低,而 ψsats -ψtlps 逐渐增加;AWC和RCF则表现为 4月份、10月份和苗期高于 6月份、8月份及幼树。其变化特点有利于增强树种的抗旱能力,反映了 4个树种在季节变化、年龄变化中历经逆境锻炼,抗旱性由弱到强的形成过程。4个树种对水分亏缺的适应机制可归结为:随组织含水量或水势降低,潜在的细胞浓度增加,组织细胞忍耐高渗透压的能力逐步增强,渗透调节能力增大,细胞壁弹性增加,维持膨压能力和原生质忍耐脱水能力增强。坐标综合评定的结果表明, 4个树种的抗旱能力从大到小的顺序是:青檀>榔榆>白榆>朴树。

The changes of main water parameters,including ψ^(sat)_s(maximum osmotic potential at water saturation point),ψ^(tlp)_s(osmotic potential when a plasmolysis just emerges),∣ψ^(sat)_s-ψ^(tlp)_s∣(difference of osmotic potential ),F_(tlp)(relative content of osmotic water when a plasmolysis just emerges),RWC_(tlp)(relative water content when a plasmolysis just emerges),AWC(relative water content in apoplast),RCF(ratio of combined water to free water)and ε(holological elastic modulus of branches),in Pteroceltis tatarinowii,Celtis sinensis,Ulmus parvifolia and Ulmus pumila with season and age were studied by means of pressure-volume curve.The results showed that these water parameters of four tree species changed in response to the changes of season and age.The ψ^(sat)_s,ψ^(tlp)_s and ε reduced with season and age,however,the change trend of∣ψ^(sat)_s-ψ^(tlp)_s∣was opposite.The AWC and the RCF were higher in April,October and in seedlings than in June,August and in young trees.The changes of these water parameters were beneficial to enhance the drought-resistant of four tree species. The drought-resistant ability of them become more and more stronger by hardening.The adaptive mechanic of these tree species to water deficit were rather consistent. The potential concentration of cell liquid and the elasticity of cell wall increased, both the ability of tissue cell to tolerant high osmotic pressure and of osmotic adjustment enhanced, and the ability of keeping turgor pressure and desiccation tolerance of protoplast strengthened.By coordinate composite evaluating, the results indicated that the drought-resistance ability of Pteroceltis tatarinowii was first,the Ulmus parvifolia was second, and the Ulmus pumila was third,the Celtis sinensis was inferior.