Davey Martin C
British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley, Cambridge CB3 0ET, UK fax: (0)1223-362616; e-mail:
Oecologia. 1997 Mar;110(1):25-31. doi: 10.1007/s004420050129.
The effects of dehydration and rehydration on carbon exchange in 14 bryophytes from the maritime Antarctic were investigated using an infra-red gas analysis system. Continuous long-term (1-12 months) and repeated (1-6 one-month cycles) desiccation responses were investigated under controlled conditions. Loss of photosynthetic rate increased with length of dehydration period in all species, although some desiccation tolerance was observed even in those bryophytes from the most hydric habitats. Percentage retention of photosynthetic rate increased from hydric to xeric species, but this pattern was not repeated in terms of absolute rates of carbon fixation due to the high initial rates in the hydric species. Repeated cycles caused a greater loss of photosynthetic rate than continuous dehydration in hydric species, but the opposite situation occurred in mesic and xeric mosses. The latter groups were possibly better able to utilise the short periods of rehydration during cycles. In most bryophytes an increase in the percentage loss of photosynthetic rate following dehydration-rehydration occurred from spring to summer to autumn samples. This pattern was clearest in the hydric species and reduced in the xeric species. These variations were largely due to changes in the initial rates of photosynthesis during the growing season. It is suggested that this increased photosynthetic capacity is stress-sensitive, and is lost during either desiccation or winter freezing; the base photosynthetic capacity, being stress-tolerant, survives either of these events. The results obtained support the hypothesis that water availability is of importance in determining the distribution of bryophytes in the Antarctic. However, only the broad scale of variation in plant communities could be explained by these observations; other factors must be important in determining the finer scale of species distribution and community composition. The results are applicable to attempts to model the productivity of Antarctic bryophytes from known or predicted environmental data.
利用红外气体分析系统，研究了脱水和复水对来自南极海洋的14种苔藓植物碳交换的影响。在可控条件下，研究了连续长期（1 - 12个月）和重复（1 - 6个为期1个月的周期）干燥响应。所有物种的光合速率损失均随脱水时间延长而增加，尽管即使在最湿润生境的苔藓植物中也观察到了一定的耐旱性。光合速率保留百分比从水生植物到旱生植物逐渐增加，但由于水生植物初始速率较高，就绝对碳固定速率而言，这种模式并未重复。在水生植物中，重复循环导致的光合速率损失比连续脱水更大，但在中生和旱生苔藓中情况相反。后一组可能更能利用循环过程中的短期复水。在大多数苔藓植物中，脱水 - 复水后光合速率损失百分比从春季到夏季再到秋季样本呈增加趋势。这种模式在水生植物中最为明显，在旱生植物中则有所减弱。这些变化主要是由于生长季节光合作用初始速率的变化。研究表明，这种增加的光合能力对胁迫敏感，在脱水或冬季结冰时会丧失；而基础光合能力对胁迫具有耐受性，在这些事件中均可存活。所得结果支持了以下假设：水分可利用性在决定南极苔藓植物的分布方面具有重要意义。然而，这些观察结果仅能解释植物群落的大致变化范围；其他因素在决定物种分布和群落组成的更精细尺度方面肯定也很重要。这些结果适用于根据已知或预测的环境数据对南极苔藓植物生产力进行建模的尝试。
