【摘要】 为三峡库区消落带植被恢复建设进行适生树种优选,本研究模拟三峡库区消落带土壤水分变化特征设置了常规生长水分条件、轻度干旱水分胁迫、土壤水饱和以及水淹4个不同处理组,研究落羽杉当年实生幼苗光合特性以及生理生态适应机理。研究结果表明,不同水分处理均显著影响落羽杉幼苗光合色素、叶片气体交换以及资源利用效率。其中,水淹处理组光合色素含量一直处于最低,受到的影响最大且最为明显;与轻度干旱组和水饱和处理组在干重条件下的光合色素含量和对照组并无显著差异形成鲜明对比。各组叶绿素a与b比值介于2.043~2.691之间,叶绿素与类葫萝卜素含量比则介于3.079~4.514之间。在轻度干旱水分胁迫环境下,落羽杉幼苗表现出较低的光能利用效率、CO2利用效率和净光合速率,其净光合速率比正常下降24.9%;相反在土壤饱和水与水淹环境下,其光能利用效率、CO2利用效率和净光合速率并未受到显著影响,仍保持与正常生长条件下一致的水平。在整个实验期,落羽杉幼苗各组的水分利用效率均随时间延长而持续增加,以水淹组增幅最小,常规生长组最大。研究证实落羽杉树种具有喜水和耐水淹生理学特性,完全可以考虑将落羽杉树种列为三峡库区消落带防护林体系建设树种之一,但应避免将其置于干旱环境之中。更多还原

【Abstract】 Four different kinds of water treatment were applied to examine the photosynthetic characteristics of Taxodium distichum seedlings in the hydro-fluctuation belt of the Three Gorges Reservoir Area. The aim was to shed light on the plant’s physio-ecological adaptation to changing water levels for revegetation purposes. The water treatments were normal growth water condition （CK）, light drought water stress （T1）, growth under soil water saturation （T2） and growth with soil submersion （T3）. T3 had the lowest content of photosynthetic pigment; T1 and T2 did not differ from CK in the content of chlorophylls and carotenoids. The ratio of chlorophylls a to b in four groups ranged 2.043～2.691 and chlorophylls to carotenoids 3.079～4.514. In group T1 the seedlings of T. distichum had lower apparent light use efficiency, lower apparent CO₂ use efficiency and lower net photosynthetic rate, with the net photosynthetic rate 24.9% lower than that of group CK. However, T2 and T3 did not differ from CK in apparent light use efficiency, apparent CO₂ use efficiency and net photosynthetic rate. The water use efficiency of four treatments consistently increased as treatment was prolonged; the average water use efficiency of T3 was the lowest while that of CK showed highest. Correlational analysis showed that the net photosynthetic rate of T. distichum seedlings was positively related to transpiration rate, stomatal conductance, water use efficiency, apparent light use efficiency and apparent CO₂ use efficiency, but highly negatively related to the ratio of chlorophylls a to b. Net photosynthetic rate was not significantly related with the content of chlorophylls, content of carotenoids, the ratio of chlorophylls to carotenoids, relative air humidity and intercellular CO₂ concentration. Transpiration rate positively correlated with stomatal conductance and negatively to water use efficiency. The results showed that different water treatment could effectively influence the T. distichum seedlings’ content of photosynthetic pigment, leaf gas exchange and apparent resources use efficiency. The results verified that the species T. distichum takes on the features of a water-tolerant and hydrophilic plant, which can be considered as one of the species for the building of protection forest system of the hydro-fluctuation belt in the Three Gorges Reservoir Area, and should not be planted in drought soil condition.更多还原