Modifying the floral microenvironment: elevational divergence in floral thermoregulatory mechanisms

当环境温度极热或极冷时，高度机动的动物可以迁移到适合它们热量需求的微栖息地，这被称为体温调节。然而，植物受到环境温度条件的影响，这可能不利于它们的繁殖成功。本研究将测试科罗拉多州南部落基山脉的一种野生多年生植物的高海拔种群是否在当地适应低温，并通过提高花温的机制，而低海拔种群在高环境温度下具有降低花温的适应机制。这项工作将查明花加热和冷却其内部花温的机制，并测试温度调节能力的变化如何影响植物的生殖适应性和植物与传粉者的相互作用。该奖项将让克莱姆森大学（Clemson University）的本科生参与STEM领域的研究，研究南加州植物园（South Carolina Botanical Garden）当地迷人的春季短生花卉的花卉变暖如何影响繁殖性能和授粉。随着全球气候的变化和花朵的不断提前，这项研究将告诉我们植物如何改善热应激以保持繁殖的成功。这项工作对未来野生和经济上重要的作物物种的植物繁殖具有重要意义。被子植物已经进化出各种机制来实现开花温度偏离环境条件，改善对花粉和胚珠的损害，促进传粉者的访问。迄今为止的研究都倾向于研究寒冷环境下植物变暖的机制，限制了对植物在温度梯度上的局部适应的理解，并且提供了很少的植物变冷的例子。此外，在野外条件下，将温度调节的变化与配子活力和传粉者吸引力的变化联系起来的研究很少。本研究将首先测试分布在南落基山脉大海拔梯度上广泛分布的多年生植物高海拔和低海拔种群之间的花卉温度调节差异。通过生长室实验，生成花粉和胚珠的热性能曲线，并结合延时摄影和反射光谱法确定花的增温和降温机制。最后，在高海拔和低海拔种群中，通过将花粉活力、种子结实率和传粉者访花与花温的变化联系起来，可以确定温度调节能力选择的地理差异。本研究将阐明植物热调节的复杂机制以及热调节能力对植物适应性的影响。它将揭示开花植物如何在气候变化中应对温度变化和物候变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Highly mobile animals can relocate to microhabitats that suit their thermal requirements when ambient temperatures are either extremely hot or cold, called thermoregulation. Plants however, are subject to ambient temperature conditions which can be detrimental to their reproductive success. This investigation will test whether high elevation populations of a wild perennial plant in the southern Colorado Rockies are locally adapted to cool temperatures, with mechanisms that increase flower temperature, whereas low elevation populations have adaptive mechanisms to lower flower temperatures under high ambient temperatures. The work will pinpoint the mechanisms by which flowers warm and cool their internal floral temperatures and test how variation in thermoregulatory ability impacts plant reproductive fitness and plant-pollinator interactions. This award will involve undergraduates at Clemson University in research in STEM fields through studies on how floral warming in local, charismatic spring ephemeral flowers impacts reproductive performance and pollination at the South Carolina Botanical Garden. As climates are changing globally and flowers continue to emerge earlier, this research will inform how plants will ameliorate thermal stress to maintain reproductive success. This work has important implications for the future of plant reproduction in both wild and economically important crop species. Angiosperms have evolved various mechanisms to achieve floral temperatures that deviate from ambient conditions, ameliorating damage to pollen and ovules and promoting pollinator visitation. Research to date is biased towards examining mechanisms of floral warming in cold environments, limiting the understanding of local adaptation in floral thermoregulation across thermal gradients and providing few examples of floral cooling. Additionally, studies linking variation in thermoregulation with variation in both gamete viability and pollinator-attraction in field conditions are scarce. This study will first test for differences in floral thermoregulation between high and low elevation populations of a widespread perennial distributed across a large altitudinal gradient in the Southern Rocky Mountains. Using growth-chamber experiments, thermal performance curves for pollen and ovule performance will be generated, and mechanisms of floral warming and cooling will be pinpointed using a combination of time-lapse photography and reflectance spectrometry. Finally, geographic variation in selection on thermoregulatory ability will be determined by linking pollen viability, seed set, and pollinator visitation with variation in floral temperature in both high and low elevation populations. This work will elucidate the complex mechanisms of floral thermoregulation and the impacts of thermoregulatory ability on plant fitness. It will shed light on how flowering plants may cope with changing temperatures and advancing phenologies in changing climates.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.