不同微生境中水光温变化对毛尖紫萼藓叶绿素荧光特性的影响

毛尖紫萼藓（Grimmia pilifera）多生长在裸岩表面且具有多种微生境，其生长过程受到水分、光照和温度等环境因素的交互影响，但其光合生理特征如何响应这种变化的环境条件尚不清楚。开展原位（荫蔽和向阳裸岩2种微生境）和室内模拟实验，分析了不同水分（模拟降水量和降水频次）、光照、温度及其复合梯度处理对毛尖紫萼藓叶绿素荧光特性的影响。原位实验结果显示荫蔽生境原位生长毛尖紫萼藓光化学效率显著高于向阳生境。在室内相同培养条件下，脱水过程中来自荫蔽生境植株有效光合效率保持时间比向阳生境明显缩短，表现出较低的脱水耐受性。水-光-温复合模拟实验显示，降水频次和光-温变化对毛尖紫萼藓光化学效率均有极显著影响且存在一定的交互作用，而降水量的影响相对较弱；弱光低温及1次/（2 d）的降水频率条件下毛尖紫萼藓具有最高的光合活性。总体来看，荫蔽生境、弱光低温条件及中等频次降水有利于毛尖紫萼藓生长，但向阳生境毛尖紫萼藓则具有更强的环境耐受性。

Effects of water-light-temperature changes in different microhabitats on chlorophyll fluorescence characteristics of Grimmia pilifera

Mosses play a pioneer role in succession series in terrestrial ecosystems and thus present important ecological functions. After long-term evolutionary adaptation, mosses have formed certain morphological, physiological, and genetic regulatory strategies to avoid adverse conditions. Mosses live in complex and diverse microhabitats, among which shaded and exposed habitats are the two most common types. Differences among these microenvironments are mainly reflected in changes in water, temperature, and light. In contrast to other substrates, rocks inhabited by saxicolous drought-tolerant mosses are absolutely dry substrates with strong daily variations in surface temperature and ineffective water retention. These characteristics present great challenges to the survival of saxicolous drought-tolerant mosses. The moss Grimmia pilifera is a model drought-tolerant moss that is widely distributed in China. It generally grows on exposed rock surfaces with variable microhabitats. Its growth is affected by the interaction of water, light, and temperature. However, we know little about how its photosynthetic characteristics respond to varied environmental conditions. In this study, in situ (exposed and shaded microhabitats) and indoor simulation experiments were carried out to test the effects of different water (simulated precipitation and precipitation frequency) conditions, light, temperature, and their combined gradients on the chlorophyll fluorescence characteristics of G. pilifera. The results of the in situ experiment showed that the photochemical efficiency of G. pilifera in the in situ shaded habitat was significantly higher than that in the exposed habitat. Under the same indoor culture conditions, the duration of the effective photosynthetic efficiency of moss individuals in the shaded habitat during dehydration was obviously shortened compared with that of moss individuals in the exposed habitat, indicating reduced dehydration tolerance. The combined simulation experiment on water, light, and temperature showed that precipitation frequency and light temperature exerted highly significant effects on the photochemical efficiency of G. pilifera and exhibited a certain interaction. However, precipitation (water quantity) had a weak influence. G. pilifera showed the highest photochemical efficiency under the conditions of low light temperature and/or the precipitation frequency of one time per 2 days. Consequently, shaded habitat, low light temperature, and moderate precipitation frequency were conducive to the growth of G. pilifera. However, G. pilifera in the exposed habitat had stronger environmental tolerance than G. pilifera in the shaded habitat. This characteristic indicated that once the shaded microenvironment is destroyed (for example, through the death and removal of vascular plants), mosses in this habitat will face a severe test of survival. In addition, our results also revealed that low-light and low-temperature conditions and moderate simulated precipitation frequency were beneficial to the individual growth of G. pilifera, showing certain indicative importance for indoor culture research.