Matthes-Sears U, Kelly P E, Larson D W
Department of Botany, University of Guelph, N1G 2W1, Guelph, Ontario, Canada.
Oecologia. 1993 Mar;95(1):9-13. doi: 10.1007/BF00649500.
This study was carried out to determine if the desiccation-tolerant fernPolypodium virgimanum L. ecologically resembles lower plants by absorbing atmospheric water through its fronds and actively growing in early spring when the soil along cliff edges is still frozen. Three times between February and April, 1991,P. virginianum clonal mats were treated with deuterium-labelled water. Following each application, fronds were collected over several days and analyzed for the presence of deuterium. Two treatment groups plus a control were used: fronds were sprayed directly while covering the soil, or the roots were watered while protecting the fronds. The control mats were left untreated. Soil, air, and frond temperatures, plus photosynthesis and frond conductance were monitored throughout the study period. At subfreezing temperatures in February, no labelled water was taken up from the soil and no photosynthesis took place. Small amounts of label were absorbed from the soil in March during freeze-thaw cycles when rates of photosynthesis and stomatal conductance were both low. Large amounts of label were taken up from the soil in April when the soil was fully thawed and gas exchange was at normal seasonal levels. Label was not absorbed directly through the fronds when the plants were actively growing. Despite the desiccation tolerance ofP. virginianum, the timing and patterns of its water uptake and gas exchange in early spring resemble those found in higher vascular plants, not poikilohydric lower plants.
本研究旨在确定耐旱蕨类植物弗吉尼亚水龙骨（Polypodium virgimanum L.）在生态上是否类似于低等植物，即通过其叶片吸收大气中的水分，并在早春悬崖边缘的土壤仍处于冻结状态时积极生长。1991年2月至4月间，对弗吉尼亚水龙骨的克隆垫进行了三次氘标记水处理。每次处理后，在几天内收集叶片并分析其中氘的存在情况。实验设置了两个处理组和一个对照组：一组是在覆盖土壤的同时直接对叶片进行喷雾处理，另一组是在保护叶片的同时对根部浇水。对照组的克隆垫不做处理。在整个研究期间，监测土壤、空气和叶片温度，以及光合作用和叶片导度。2月处于冰点以下温度时，植物未从土壤中吸收标记水，也未进行光合作用。3月在冻融循环期间，光合作用速率和气孔导度都较低，植物从土壤中吸收了少量标记水。4月土壤完全解冻且气体交换处于正常季节水平时，植物从土壤中吸收了大量标记水。当植物处于活跃生长状态时，标记水不会直接通过叶片被吸收。尽管弗吉尼亚水龙骨具有耐旱性，但其早春吸水和气体交换的时间及模式与高等维管植物相似，而非变水的低等植物。
