Temperature effects on pollen performance and their consequences for seed reproduction in wild plants

环境与植物有性生殖成功之间的密切联系早已为人所知。然而，由于气候变化对种子作物的潜在负面影响，即短期作物歉收和长期种子产量下降，在过去二十年中，它受到了越来越多的关注。大量研究表明，气候变化引起的种子质量和数量的变化不可避免地导致植物生物学、生态学和分布的变化。当观察种子生产的不同阶段时，花粉已被证明是对温度最敏感的，因此是植物有性繁殖的最受限制的部分。在温度胁迫下，由于小的、单倍体的、未受保护的雄性配子体直接暴露在恶劣环境中，植物往往产生较少的、质量较低的花粉。为了应对这种胁迫，植物在不同的组织水平上发展出多种策略，显示出生殖反应的可塑性，以确保受精。然而，由于多种知识空白（例如，生物化学和生理研究的强大优势，对作物和模式植物物种的强烈关注），我们仍然不确定雄性配子体性能在特定热条件下的可塑性如何，以及这种可塑性在多大程度上允许植物调整种子生产以适应不断变化的环境，特别是在野生植物中。在这里，我们建议在个体、种内和种间水平上详细研究温度对花粉性能（PP，即影响其成功受精能力的雄性配子体的总共10个功能性状）的影响，并评估它们对野生（即非栽培、非模式）植物种子再生成功的潜在重要性。具体目标是：1)估计单株PP在气候条件年际变化中的可塑性；2)评估野生植物群体中PP的种内变异水平；3)评估PP在群体和物种水平上对高温胁迫的适应性；4)确定PP的热上限并估计其沿气候梯度的变化。该项目成果将通过加深对温度如何影响不同水平花粉性能及其对高温胁迫的易感性的理解来促进生态学的发展，随着气候变化的继续，这一认识将会增加。

The close link between the environment and success of plant sexual reproduction has been known for a long time. Yet, it has received increased interest over last two decades, due to the potential negative consequences of climate change on seed crops, namely short-term crop failure and long-term reduction in seed yields. Numerous studies provide evidence that this climate change-induced variation in seed quality and quantity inevitably leads to alternations in plant biology, ecology and distribution. When looking at the different stages of seed production, pollen has been shown to be the most temperature sensitive and thus the most limiting part of plant sexual reproduction. Under temperature stress, plants always tend to produce less pollen of lower quality, due to the direct exposure of small, haploid, unprotected male gametophytes to the hostile environment. In order to cope with this stress, plants have developed several strategies at different levels of their organization showing plasticity in their reproductive response to ensure fertilization. However, due to multiple knowledge gaps (e.g. strong dominance of biochemical and physiological studies, strong focus on crop and model plant species), we are still uncertain of how plastic the male gametophyte performance is in response to given thermal conditions and to what extent this plasticity allows plants to adjust seed production to a changing environment, especially in wild plants. Here we propose to examine in detail the temperature effects on pollen performance (PP; expressly in total ten functional traits of the male gametophyte that influence its ability to achieve successful fertilization) at the individual, intraspecific, and interspecific levels, and evaluate their potential importance for the success of plant seed regeneration in wild (i.e. non-cultivated, non-model) species. The specific aims are to: 1) estimate the plasticity of individual plant PP with regards to interannual variation in weather conditions, 2) evaluate the level of intraspecific variability in PP in wild plant populations, 3) assess the adaptability of PP to high-temperature stress at population and species levels and 4) determine the upper thermal limits of PP and estimate its variation along climatic gradients.The project results will progress ecology by increasing understanding on how temperature affects pollen performance at different levels and its susceptibility to high-temperature stress, which will increase as climate change goes on.