In situ studies of water relations and CO2 exchange of the tropical macrolichen, Sticta tomentosa
In situ studies of water relations and CO2 exchange of the tropical macrolichen, Sticta tomentosa
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热带大型地衣 Sticta tomentosa 的水关系和 CO2 交换的原位研究
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
O. Lange
中科院分区：
文献类型：
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作者：
G. Zotz;B. Büdel;A. Meyer;H. Zellner;O. Lange
在巴拿马低山地热带雨林的森林边缘，测量了叶状地衣Sticta tomentosa(Swartz)Ach.的CO2交换、水分关系和小气候的Diel(24-h)时间进程，以及对实验条件的响应。与早先对其他两种热带雨林地衣的观察类似，在光照最高的时期，每日干燥抑制了净光合作用(NP)。毫不奇怪，NP的光响应曲线在相当弱的光照下表现出饱和。复水作用与最初的短时间再饱和爆发有关，这在自然条件下和实验条件下都可以得到证实。这种额外的二氧化碳损失似乎太低了，与生态无关。此外，较高的菌体水合作用也不利于NP：在最大含水率时，净CO2吸收被抑制50%。虽然NP很好地适应了盛行的高温，但后者也刺激了暗呼吸。平均而言，几乎60%的日碳增量在夜间丢失。尽管有这些限制，24小时的综合C增益相当高，平均为菌体C含量的0.5%。虽然这些数据是针对水平暴露的样品确定的，但我们也评估了不同暴露对光合作用表现的影响。Diel C的增益在允许长时间活动的半遮荫(西风)条件下最高，而在其他暴露条件下更高的光照度不能用于光合作用生产：向东暴露的菌体干涸甚至比水平暴露的样品更快。
Diel (24-h) time courses of CO 2 exchange, water relations, and microclimate of the foliose lichen, Sticta tomentosa (Swartz) Ach., and responses to experimentally manipulated conditions were measured at a forest edge in a lower montane rainforest in Panama. Similar to earlier observations on two other rain forest lichens, daily desiccation suppressed net photosynthesis (NP) during the period when irradiation was highest. Not surprisingly, the light response curves of NP showed saturation at rather low light levels. Rehydration was associated with an initial resaturation burst of short duration, which could be demonstrated both under natural conditions and experimentally. This additional loss of CO 2 seems too low to be ecologically relevant. Moreover, high thallus hydration was also detrimental to NP: at maximum water content net CO 2 uptake was depressed by > 50%. Although NP was well adapted to the prevailing high temperatures, the latter also stimulated dark respiration. On average, almost 60 % of the diurnal carbon gain was lost during the night. In spite of these limitations, the integrated 24-h C gain was quite high, on average 0.5 % of the thallus C content. Whilst these figures were determined for horizontally exposed samples, we also assessed the role of different exposures on photosynthetic performance. Diel C gain was highest under conditions of semi-shade (westerly exposure), which allowed long periods of activity, whilst much higher irradiance at other exposures could not be utilized for photosynthetic production: easterly exposed thalli dried out even faster than horizontally exposed samples.