Degrees of crassulacean acid metabolism in tropical epiphytic and lithophytic ferns
Degrees of crassulacean acid metabolism in tropical epiphytic and lithophytic ferns
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DOI：
10.1071/pp99001
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发表时间：
1999-01-01
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影响因子：
--
通讯作者：
Winter, K
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文献类型：
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作者：
Holtum, JAM;Winter, K
本文报道了3种热带蕨类植物的景天科酸代谢（CAM），即附生植物星蕨（Microsorium punctatum）、厚叶水龙骨（Polypodium crassifolium）和石生植物扁蕨（Platycerium veitchii）。粗叶水龙骨和魏氏水龙骨表现出弱CAM特征。虽然没有观察到夜间CO2净吸收，但CAM的存在是从夜间可滴定酸度分别增加4.7和4.1 mu equiv（g fr wt）（-1），在黑暗期的前半段期间净CO2释放速率降低，以及在早期光照期期间净CO2吸收存在CAM样降低来推断的。In M. punctatum净CO2吸收在前半段的黑暗时期是伴随着增加的可滴定酸度的39.2 μ equiv（g fr wt）-1和一个显着减少净CO2吸收在早期的光周期。当对厚叶杨和M. punctatum，净CO2吸收在光显着减少，但没有改变的程度或模式的CO2交换在黑暗中。因此，由于在黑暗中固定CO2而获得的碳的比例分别从2.8%和10%增加到63.5%和49.3%（100%是在光照期间的净CO2吸收加上在黑暗期间的估计CO2吸收）。在不添加水的情况下9天后，暗CO2吸收负责在厚叶松中维持24 h的净碳增益。Platycerium veitchii、厚叶悬铃木P. crassifolium和M. punctatum的碳同位素比在-25.9和-22.6 ‰之间，表明碳同位素比本身可能不足以鉴定弱CAM。我们认为，CAM可能是更普遍的热带附生和石生蕨类植物比目前设想的。
Crassulacean acid metabolism (CAM) was observed in three species of tropical ferns, the epiphytes Microsorium punctatum and Polypodium crassifolium and the lithophyte Platycerium veitchii. Polypodium crassifolium and P. veitchii exhibited characteristics of weak CAM. Although no net nocturnal CO2 uptake was observed, the presence of CAM was inferred from nocturnal increases in titratable acidity of 4.7 and 4.1 mu equiv (g fr wt)(-1) respectively, a reduction in the rates of net CO2 evolution during the first half of the dark period, and the presence of a CAM-like decrease in net CO2 uptake during the early light period. In M. punctatum net CO2 uptake during the first half of the dark period was accompanied by an increase in titratable acidity of 39.2 mu equiv (g fr wt) -1 and a pronounced reduction in net CO2 uptake during the early light period. When water was withheld from P. crassifolium and M. punctatum, net CO2 uptake during the light was reduced markedly but there was no change in the extent or patterns of CO2 exchange in the dark. As a consequence, the proportion of carbon gained due to CO2 fixation in the dark increased from 2.8 and 10% to 63.5 and 49.3%, respectively (100% being net CO2 uptake during the light plus the estimated CO2 uptake during the dark). After 9 days without added water, dark CO2 uptake was responsible for the maintenance of a net 24 h carbon gain in P. crassifolium. Platycerium veitchii, P. crassifolium and M. punctatum exhibited carbon isotope ratios of between -25.9 and -22.6 parts per thousand indicating that carbon isotope ratios may not, by themselves, be sufficient for the identification of weak CAM. We suggest that CAM may be more prevalent in tropical epiphytic and lithophytic ferns than currently envisaged.