Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia.
Plant Biol (Stuttg). 2010 Sep 1;12(5):743-54. doi: 10.1111/j.1438-8677.2009.00285.x.
Light availability varies strongly among moss habitats and within the moss canopy, and vertical variation in light within the canopy further interacts with the age gradient. The interacting controls by habitat and canopy light gradient and senescence have not been studied extensively. We measured light profiles, chlorophyll (Chl), carotenoid (Car) and nitrogen (N) concentrations, and photosynthetic electron transport capacity (J(max)) along habitat and canopy light gradients in the widespread, temperate moss Pleurozium schreberi to separate sources of variation in moss chemical and physiological traits. We hypothesised that this species, like typical feather mosses with both apical and lateral growth, exhibits greater plasticity in the canopy than between habitats due to deeper within-canopy light gradients. For the among-habitat light gradient, Chl, Chl/N and Chl/Car ratio increased with decreasing light availability, indicating enhanced light harvesting in lower light and higher capacity for photoprotection in higher light. N and J(max) were independent of habitat light availability. Within the upper canopy, until 50-60% above-canopy light, changes in moss chemistry and photosynthetic characteristics were analogous to patterns observed for the between-habitat light gradient. In contrast, deeper canopy layers reflected senescence of moss shoots, with pigment and nitrogen concentrations and photosynthetic capacity decreasing with light availability. Thus, variation in chemical and physiological traits within the moss canopy is a balance between acclimation and senescence. This study demonstrates extensive light-dependent variation in moss photosynthetic traits, but also that between-habitat and within-canopy light gradient affects moss physiology and chemistry differently.
光可用性在苔藓栖息地和苔藓冠层内变化很大，冠层内的垂直光变化进一步与年龄梯度相互作用。栖息地和冠层光梯度以及衰老的相互控制作用尚未得到广泛研究。我们沿着广泛分布的温带苔藓 Pleurozium schreberi 的栖息地和冠层光梯度测量了光分布、叶绿素（Chl）、类胡萝卜素（Car）和氮（N）浓度以及光合作用电子传递能力（J(max)），以分离苔藓化学和生理特征的变异来源。我们假设，这种物种，像具有顶生和侧生生长的典型羽毛苔藓一样，由于冠层内更深的光梯度，在冠层中比在栖息地之间表现出更大的可塑性。对于栖息地之间的光梯度，Chl、Chl/N 和 Chl/Car 比随着光可用性的降低而增加，表明在较低光下增强了光捕获，在较高光下增强了光保护能力。N 和 J(max) 与栖息地的光可用性无关。在上冠层中，直到冠层上方 50-60%的光，苔藓化学和光合作用特征的变化与在栖息地之间的光梯度中观察到的模式相似。相比之下，更深的冠层层反映了苔藓芽的衰老，随着光可用性的降低，色素和氮浓度以及光合作用能力降低。因此，苔藓冠层内化学和生理特征的变化是适应和衰老之间的平衡。这项研究表明苔藓光合作用特征具有广泛的光依赖性变化，但也表明栖息地之间和冠层内的光梯度对苔藓生理学和化学的影响不同。
