哀牢山湿性常绿阔叶林树干4种附生苔藓植物的水分变化对光合、荧光参数的影响

以云南哀牢山湿性常绿阔叶林中的附生苔藓植物为对象,研究林内4种树干附生苔藓植物阿萨羽苔(Plagiochila assamica Steph.)、西南树平藓(Homaliodendron montagneanum(Müll.Hal.)M.Fleisch.)、刀叶树平藓(H.scalpellifolium(Mitt.)M.Fleisch.)、大羽藓(Thuidium cymbifolium(Dozy et Molk.)Dozy et Molk.)的吸水力、失水特征和脱水耐性,稳定碳同位素(δ~(13)C)值,以及水分变化对苔藓净光合速率和荧光参数的影响。结果显示:(1)4种附生苔藓植物均具有较强的吸水能力和较低持水力,脱水耐性较强,脱水后均可迅速复水;(2)4种附生苔藓植物的δ~(13)C值较低,其水分利用效率小于其他维管束植物;除大羽藓外,其余3种附生苔藓雨季的δ~(13)C值与水分利用效率均高于干季;(3)4种附生苔藓植物的净光合速率(Pn)随着含水量的降低而降低,在含水量小于60%~80%时,其最大光化学效率(Fv/Fm)急剧下降,反映出这些附生苔藓植物的光合、荧光特性对水分变化非常敏感。

Effects of water content change on photosynthetic and fluorescence parameters of four bole epiphytic bryophytes in montane moist evergreen broad-leaved forest in the Ailao Mountains

The water absorption capacity, water release, desiccation tolerance,stable carbon isotope (δ¹³C) values, and effects of water content change on photosynthetic and fluorescence parameters of four bole epiphytic bryophytes, Plagiochila assamica Steph., Homaliodendron montagneanum (Müll. Hal.) M. Fleisch., H. scalpellifolium (Mitt.) M. Fleisch., and Thuidium cymbifolium (Dozy et Molk.) Dozy et Molk., were investigated from the montane moist evergreen broad-leaved forest of the Ailao Mountains, Yunnan, China. Results showed that:(1) all species had high water absorption rates, low water-holding capacities, and strong desiccation tolerances, and all exhibited quick resilience after dehydration; (2) the δ¹³C values and water use efficiency of the four bryophytes were lower than those of vascular plants. Except for T. cymbifolium, the δ¹³C values and water use efficiency of the other three bryophytes in the rainy season were higher than those in the dry season; and (3) the net photosynthetic rates (P_n) of the four epiphytic bryophytes declined with decreasing water content. The maximum photochemical efficiency parameter (F_v/F_m) declined sharply under water content conditions of less than 60%~80%, indicating that the photosynthetic and fluorescence properties of the four bryophytes were very sensitive to moisture change.