Wu Fujia, Chen Xincong, Guo Yangping, Liu Wenwen, Zhang Yihui
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian, China.
Front Plant Sci. 2024 Nov 26;15:1491275. doi: 10.3389/fpls.2024.1491275. eCollection 2024.
Cold stratification has a pronounced influence on seed germination, climate change is altering cold stratification regimes across climatic zones. Therefore, it is urgent to explore how seed germination from different geographic provenances responds to these changes. The invasive plant Spartina alterniflora spans three climatic zones along the Chinese coast, such distribution provides a natural temperature gradient to explore how warming alters the effects of cold stratification on germination.
Spartina alterniflora seeds were collected from nine locations across three climatic zones in China from September to November in 2021. Seeds were planted in three common gardens with three latitude gradients of 21 °N, 28 °N, and 38 °N, after 0-month and 4-month cold stratification at 4 °C in November 2021 and March 2022, respectively. Each common garden simulated the natural temperature conditions and shield the plants from rain.
Results showed that cold stratification led to explosive germination and rapidly reaching a plateau, shortened the germination time and improved the final germination rate. These effects were magnified from the high-latitude garden to the low-latitude one (i.e., warming). And the interactive effect of cold stratification and warming varied among provenances. For the subtropical and temperate provenances, the improvement in germination rate induced by cold stratification gradually increased from high-latitude garden to low-latitude one, while for tropical provenances, this difference progressively decreased. Discussion: Thus, our results indicated that subtropical and temperate provenances may migrate northward for adequate low temperatures to ensure high germination rate, because cold stratification can alleviate the negative impacts of warming on germination. For the tropical provenances, warming also suppressed the advantage that cold stratification provides in enhancing the germination rate, which may hinder their further spread southward. Our study contributes to understanding the responses of vegetation germination and recruitment across different climatic zones under global warming, providing insights for the distribution of cosmopolitan species and the management of exotic species.
低温层积对种子萌发有显著影响，气候变化正在改变各气候带的低温层积模式。因此，迫切需要探索不同地理种源的种子萌发如何应对这些变化。入侵植物互花米草在中国沿海跨越三个气候带，这种分布提供了一个自然温度梯度，以探究气候变暖如何改变低温层积对萌发的影响。
2021年9月至11月，从中国三个气候带的九个地点采集互花米草种子。种子分别于2021年11月和2022年3月在4℃下进行0个月和4个月的低温层积处理后，种植在三个具有21°N、28°N和38°N三个纬度梯度的共同花园中。每个共同花园模拟自然温度条件并为植物遮雨。
结果表明，低温层积导致种子爆发式萌发并迅速达到平台期，缩短了萌发时间并提高了最终萌发率。这些效应从高纬度花园到低纬度花园逐渐放大（即气候变暖）。并且低温层积和气候变暖的交互效应因种源而异。对于亚热带和温带种源，低温层积诱导的萌发率提高从高纬度花园到低纬度花园逐渐增加，而对于热带种源，这种差异逐渐减小。讨论：因此，我们的结果表明，亚热带和温带种源可能向北迁移以获取足够的低温以确保高萌发率，因为低温层积可以减轻气候变暖对萌发的负面影响。对于热带种源，气候变暖也抑制了低温层积在提高萌发率方面的优势，这可能阻碍它们进一步向南扩散。我们的研究有助于理解全球变暖下不同气候带植被萌发和更新的响应，为广布种的分布和外来物种的管理提供见解。
