Department of Biological Sciences, Aquatic Biology Program, University of Alabama, Tuscaloosa, Alabama 35487-0206.
Appl Environ Microbiol. 1998 Feb;64(2):607-12. doi: 10.1128/AEM.64.2.607-612.1998.
Standing litter of emergent macrophytes often forms a major portion of the detrital mass in wetland habitats. Microbial assemblages inhabiting this detritus must adapt physiologically to daily fluctuations in temperature and water availability. We examined the effects of various environmental conditions on the concentrations of osmoregulatory solutes (polyols and trehalose) and the respiratory activities of fungal assemblages inhabiting standing litter of the freshwater emergent macrophyte Juncus effusus. Under field conditions, the concentrations of osmolytes (polyols plus trehalose) in fungal decomposers were negatively correlated with plant litter water potentials (r = -0.75, P < 0.001) and rates of microbial respiration (r = -0.66, P < 0.001). The highest concentration of osmolytes (polyols plus trehalose) occurred in standing litter exposed to desiccating conditions (range from wet to dry, 0.06 to 0.68 mumol . mg of fungal biomass). Similar fluctuations in polyol and trehalose concentrations were observed in standing litter wetted and dried under laboratory conditions and for four predominant fungal decomposers of J. effusus grown individually on sterilized Juncus leaves. These studies suggest that fungal inhabitants associated with standing litter of emergent macrophytes can adjust their intracellular solute concentrations in response to daily fluctuations in water availability.
挺水植物的凋落物常常是湿地生境中碎屑物质的主要组成部分。栖息在这些碎屑中的微生物群落必须在生理上适应温度和水分可利用性的日常波动。我们研究了各种环境条件对栖息在淡水挺水植物蔺草凋落物上的真菌群落的渗透调节溶质（多元醇和海藻糖）浓度和呼吸活性的影响。在野外条件下，真菌分解者中的渗透溶质（多元醇加海藻糖）浓度与植物凋落物水势（r = -0.75，P < 0.001）和微生物呼吸速率（r = -0.66，P < 0.001）呈负相关。在暴露于干燥条件下的凋落物（从湿到干，0.06 到 0.68 mumol. mg 的真菌生物量）中，发现了最高浓度的渗透溶质（多元醇加海藻糖）。在实验室条件下，对挺水植物凋落物进行加湿和干燥，以及对蔺草的四个主要真菌分解者在灭菌的蔺草叶片上单独培养时，观察到多元醇和海藻糖浓度的类似波动。这些研究表明，与挺水植物凋落物有关的真菌栖息者可以根据水分可利用性的日常波动来调节其细胞内溶质浓度。
