Murray K J, Tenhunen J D, Nowak R S
Department of Biological Sciences, University of Nevada Las Vegas, Box 454004, 89154-4004, Las Vegas, NV, USA.
Bayreuth Institute for Terrestrial Ecosystem Research (BITÖK), University of Bayreuth, 95440, Bayreuth, Germany.
Oecologia. 1993 Nov;96(2):200-207. doi: 10.1007/BF00317733.
The effect of high light intensity on photosynthesis and growth of Sphagnum moss species from Alaskan arctic tundra was studied under field and laboratory conditions. Field experiments consisted of experimental shading of mosses at sites normally exposed to full ambient irradiance, and removal of the vascular plant canopy from above mosses in tundra water track habitats. Moss growth was then monitored in the experimental plots and in adjacent control areas for 50 days from late June to early August 1988. In shaded plots total moss growth was 2-3 times higher than that measured in control plots, while significant reductions in moss growth were found in canopy removal plots. The possibility that photoinhibition of photosynthesis might occur under high-light conditions and affect growth was studied under controlled laboratory conditions with mosses collected from the arctic study site, as well as from a temperate location in the Sierra Nevada, California. After 2 days of high-light treatment (800 μmol photons m s) in a controlled environmental chamber, moss photosynthetic capacity was significantly lowered in both arctic and temperate samples, and did not recover during the 14-day experimental period. The observed decrease in photosynthetic capacity was correlated (r =0.735, P<0.001) with a decrease in the ratio of variable to maximum chlorophyll fluorescence (F /F ) in arctic and temperate mosses. This relationship indicates photoinhibition of photosynthesis in both arctic and temperate mosses at even moderately high light intensities. It is suggested that susceptibility to photoinhibition and failure to photoacclimate to higher light intensities in Sphagnum spp. may be related to low tissue nitrogen levels in these exclusively ombrotrophic plants. Photoinhibition of photosynthesis leading to lowered annual carbon gain in Sphagnum mosses may be an important factor affecting CO flux at the ecosystem level, given the abundance of these plants in Alaskan tussock tundra.
在野外和实验室条件下，研究了高光强度对阿拉斯加北极苔原泥炭藓物种光合作用和生长的影响。野外实验包括在通常暴露于全环境辐照度的地点对苔藓进行实验性遮荫，以及在苔原水道栖息地从苔藓上方移除维管植物冠层。然后在1988年6月下旬至8月上旬的50天内，在实验地块和相邻对照区域监测苔藓生长情况。在遮荫地块，苔藓总生长量比对照地块测量值高2至3倍，而在冠层移除地块发现苔藓生长显著减少。利用从北极研究地点以及加利福尼亚内华达山脉的一个温带地点采集的苔藓，在受控实验室条件下研究了高光条件下可能发生光合作用光抑制并影响生长的可能性。在受控环境箱中进行2天的高光处理（800 μmol光子·m⁻²·s⁻¹）后，北极和温带样本的苔藓光合能力均显著降低，且在14天的实验期内未恢复。观察到的光合能力下降与北极和温带苔藓中可变叶绿素荧光与最大叶绿素荧光之比（Fv/Fm）的下降相关（r = 0.735，P < 0.001）。这种关系表明，即使在适度高光强度下，北极和温带苔藓中也存在光合作用光抑制。有人认为，泥炭藓属植物对光抑制的敏感性以及无法对更高光强度进行光适应，可能与这些完全依赖雨水补给营养的植物中低组织氮水平有关。鉴于阿拉斯加丘状苔原中这些植物数量众多，光合作用光抑制导致泥炭藓年碳增益降低可能是影响生态系统水平CO₂通量的一个重要因素。
