模拟增温条件下沉水植物菹草的有性与无性繁殖策略研究

Sexual and asexual reproductive strategies of submerged plant,Potamogeton crispus L.,under simulated warming

以北温带4个不同地理来源的广布性沉水植物菹草(Potamogeton crispus L.)休眠芽为对象,使用玻璃温室模拟增温状态(2℃~5.8℃),以不同克隆种群所产生的休眠芽和果的数量与生物量为指标,对不同增温状态下菹草的无性和有性繁殖策略进行研究,并根据菹草休眠芽苞叶数和无性繁殖体适合度的潜在关系对休眠芽进行分型:贫叶芽(苞叶数≤4)和富叶芽(苞叶数>4)。结果显示,地理来源和增温状态可显著影响菹草的繁殖。尽管模拟增温对不同地理来源菹草克隆种群产生休眠芽数量的影响具有差异,但模拟增温未导致休眠芽总生物量的下降。模拟增温导致休眠芽中贫叶芽占比的减少,从而导致富叶芽占比的增加。此外,模拟增温导致3个种群有性繁殖的丧失。由于菹草主要经由水媒传粉,推测水体的增温破坏了其花粉活力,导致有性繁殖的丧失。苞叶具有营养储藏和光合作用的功能,苞叶数与腋芽数呈正相关。推测增温条件下,菹草通过产生较大的无性繁殖体来维持其适合度,这可能是菹草在繁殖模式上应对气候变暖的策略。

The cosmopolitan submerged plant,Potamogeton crispus L.,was used as a model species to study the effects of climate warming on reproduction.Turions from four different geographic temperate regions in China were used for the mesocosm experiment.A glasshouse experiment was used to mimic climate warming of 2.0℃–5.8℃.Number and biomass of turions and fruits were selected as proxies for asexual and sexual reproduction,respectively.Based on the potential correlation between scale leaf number of the turions and fitness of asexual propagules,the turions were classified into two categories:oligophyllous(scale leaf number≤4)and pleiophyllous turions(scale leaf number>4).Geographic sources and warming conditions significantly affected asexual and sexual reproduction in P.crispus.Although simulated warming had different effects on turion number in different clonal populations,total turion biomass did not decrease.Simulated warming led to a decrease in the percentage of oligophyllous turions and an increase in the percentage of pleiophyllous tu-rions.Moreover,simulated warming led to total loss of sexual reproduction in three clonal populations.As P.crispus is mainly hydrophilous,we speculate that warming destroyed pollen viability,resulting in the total loss of sexual reproduction.The scale leaves were capable of nutrient storage and photosynthesis.Additionally,a positive correlation was found between scale leaf number and axillary bud number.We speculate that P.cris-pus maintains fitness via the production of larger-size asexual propagules under warming conditions as a re-productive life-history strategy to cope with climate warming.