低温胁迫后苔藓植物对模拟氮沉降条件的生理响应

Physiological responses of bryophytes experienced low temperature stress to simulated nitrogen deposition

2008年初受强寒潮的影响,中国华南大部分地区出现持续的异常低温。该文研究了华南地区常见的3种苔藓植物--刺边小金发藓拟刺亚种(Pogonatum cirratum subsp.fuscatum)、大灰藓(Hypnum plumaeforme)和石地钱(Reboulia hemisphaerica),在人工模拟氮(N)沉降两年并经历2008年初异常低温气候后的生理响应变化,并与2007年正常气候情况下人工加N一年后的结果进行比较,分析苔藓植物的生长与N沉降之间的关系,并探讨N沉降对低温胁迫后苔藓植物的补偿生长的影响。结果显示:2008年3种苔藓植物的净光合速率和淀粉含量在加N量为0-60kg N·hm-2·a-1的范围内均随着N浓度的上升而下降,总N含量在加N量处于0-40kg N·hm-2·a-1的范围内随着N浓度的上升而上升,至60kg N·hm-2·a-1时不再上升,甚至有所下降。2008年,3种苔藓植物大多数碳氮代谢指标在对照及低N条件下与2007年加N1年且在正常气候时同种N处理时相比均有不同程度的上升,但上升幅度与加N浓度成反比,至中高N条件时两者常较接近,显示苔藓植物在经历低温胁迫后会出现超补偿效应,但是在N沉降升高的条件下,补偿生长能力下降。

Aims Increasing N deposition and frequent abnormal weather are two characteristics of global climate change. Our objective was to study the physiological responses of bryophytes to simulated nitrogen treatments and low temperature stress to provide insights to the relationship between N deposition and compensatory effect after low temperature stress. Methods Physiological responses of three bryophyte species, Pogonatum cirratum subsp. fuscatum, Hypnum plumaeforme and Reboulia hemisphaerica, which were subjected to a 2-year-simulated N deposition and suffered a low temperature stress in early 2008, were studied and compared with the results of the bryophytes that experienced a 1-year-simulated N deposition and normal weather conditions. N treatments （Control, 20, 40 and 60 kg N·hm–2·a–1） in three replicates were established for each species. The N additions were divided into four applications per year. Important findings The results of 2008 showed that net photosynthetic rate and concentration of starch decreased with increasing N addition doses within the range of 0–60 kg N·hm–2·a–1. The concentration of total N increased with increasing N treatment doses within the range of 0–40 kg N·hm–2·a–1, but decreased at N addition doses of 60 kg N·hm–2·a–1. At control and low N addition conditions （20 kg N·hm–2·a–1）, most of the indices of carbon and nitrogen metabolism of the three bryophytes were higher than the results of 2007 of the same species at the same N treatments, but N addition depressed the increase. At high N treatment conditions （≥ 40 kg N·hm–2·a–1）, the results of 2007 and 2008 were usually similar. Results indicate that the bryophytes exhibit overcompensatory growth after experiencing a low temperature stress, but at stimulated N deposition conditions, their compensatory ability decreases.