西双版纳热带雨林中两种生态型蕨类植物的光合特性比较研究

通过比较分布于西双版纳热带雨林林下生境中的附生鸟巢蕨（Neottopteris nidus）和地生网脉铁角蕨（Asplenium finlaysonianum）的光合特征和光合诱导特性，来研究不同生态型蕨类植物的光斑利用策略。研究结果表明，2种蕨类植物的最大净光合速率、暗呼吸速率、表观量子效率、光饱和点和光补偿点没有显著差异，但网脉铁角蕨的最大气孔导度远远高于鸟巢蕨，表明后者具有更强的光合水分利用效率。在暗处理3／J＇,时接着光照（光强为20I~mol-m-2,s。‘）30分钟后，网脉铁角蕨的初始气孔导度显著高于鸟巢蕨。连续照射饱和强光后，网脉铁角蕨达到最大净光合速率50％（T50％）和90％的时间（T90%）比鸟巢蕨短：网脉铁角蕨和鸟巢蕨的T50%分别为0．57和5．31分钟，T90％分别为5．85和26．33分钟。诱导过程中，气孔导度对强光的响应明显滞后于净光合速率。鸟巢蕨达到最大气孔导度的时间明显比网脉铁角蕨慢，但在光合诱导消失过程中2种蕨类植物的光合诱导维持能力却没有显著差异。上述结果表明，与大多数地生林下植物（如网脉铁角蕨）相比，附生鸟巢蕨的水分保护比碳获得更重要，但却限制了附生蕨对光斑的利用。

Photosynthetic Induction in Two Fern Species with Different Eco-types in Xishuangbanna Tropical Rainforest

We compared the characteristics of photosynthesis and photosynthetic induction in an epiphytic fern （Neottopteris nidus） and a terrestrial fern （Asplenium finlaysonianum） in the understory of the Xishuangbanna tropicai rainforest to study the light-fleck utilization strategy in the two eco-type ferns. Maximum photosynthetic rate, dark respiration, apparent quantum yield, light saturation point and light compensation point did not differ between the two fern species. However, maximum stomatal conductance was higher in A. finlaysonianum than in N. nidus, which indicates better photosynthetic water-use efficiency in the latter species. Compared to N. nidus, A. finlaysonianum had a higher initial stomatal conductance on exposure to low light （20 μmol·m^-2·s^-1） for 30 min after 3 h dark adaptation. The time required to reach 50% （T50%） and 90% （T90%） maximal net photosynthetic rate in A. finlaysonianum was shorter than that in N. nidus （T50% 0.57 and 5.31 min, T90% 5.85 and 26.33 min in A. finlaysonianum and N. nidus, respectively）. Attaining maximal stomatal conductance significantly lagged behind the increase in net photosynthetic rate during the induction course. The time required to reach maximum stomatal conductance was longer in N. nidus than in A. finlaysonianum, but the ferns did not differ in maintaining capacity of photosynthetic induction during induction loss. Thus, water conservation takes priority over carbon gain in N. nidus, which limits the use of light flecks for CO2 fixation in this epiphytic fern as compared to most terrestrial understory plants such as A. finlaysonianum.