Institut für Botanik, Technische Universität Darmstadt, Darmstadt, Germany.
Plant Biol (Stuttg). 2010 May 1;12(3):437-44. doi: 10.1111/j.1438-8677.2009.00249.x.
The rough bark of orchard trees (Malus) around Darmstadt is predominantly covered in red to purple-brown layers (biofilms) of epiphytic terrestrial alga of Trentepohlia umbrina. The smooth bark of forest trees (Fagus sylvatica L. and Acer sp.) in the same area is covered by bright green biofilms composed of the green algae Desmococcus, Apatococcus and Trebouxia, with a few cells of Coccomyxa and 'Chlorella' trebouxioides between them. These algae are desiccation tolerant. After samples of bark with the biofilms were kept in dry air in darkness for various periods of time, potential quantum yield of PSII, F(v)/F(m), recovered during rehydration upon rewetting. The kinetics and degree of recovery depended on the length of time that the algae were kept in dry air in the desiccated state. Recovery was better for green biofilm samples, i.e. quite good even after 80 days of desiccation (F(v)/F(m) = ca. 50% of initial value), than the red samples, where recovery was only adequate up to ca. 30-40 days of desiccation (F(v)/F(m) = ca. 20-55% of initial value). It is concluded that the different bark types constitute different ecophysiological niches that can be occupied by the algae and that can be distinguished by their capacity to recover from desiccation after different times in the dry state.
达姆施塔特地区果园树木（Malus）的粗糙树皮主要覆盖着 Trentepohlia umbrina 等陆生附生藻类的红棕色至紫棕色层（生物膜）。同一地区森林树木（Fagus sylvatica L. 和 Acer sp.）的光滑树皮覆盖着由绿藻 Desmococcus、Apatococcus 和 Trebouxia 组成的亮绿色生物膜，其间有几个 Coccomyxa 和“Chlorella”trebouxioides 细胞。这些藻类具有耐旱性。将带有生物膜的树皮样本在黑暗中干燥空气中保存一段时间后，在重新润湿时，PSII 的潜在量子产量、F(v)/F(m) 在复水过程中恢复。恢复的动力学和程度取决于藻类在干燥空气中干燥保存的时间长度。对于绿色生物膜样本，恢复情况更好，即使在干燥 80 天后（F(v)/F(m)约为初始值的 50%），恢复情况也相当好，而红色样本的恢复情况仅在干燥 30-40 天后（F(v)/F(m)约为初始值的 20-55%）。这表明，不同的树皮类型构成了不同的生理生态小生境，可以被藻类占据，并且可以通过它们在不同干燥时间后的恢复能力来区分。
