Centre for Sustainable Ecosystem Services, University of Wollongong, Wollongong, NSW, Australia.
School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia.
PLoS One. 2018 Oct 11;13(10):e0204906. doi: 10.1371/journal.pone.0204906. eCollection 2018.
Future increases in the intensity of heat waves (high heat and low water availability) are predicted to be one of the most significant impacts on organisms. Using six native grasses from Eastern Australia, we assessed their capacity to tolerate heat waves with low water availability. We were interested in understanding differential response between native grasses of differing photosynthetic pathways in terms of physiological and some molecular parameters to ecologically relevant summer heat waves that are associated with low rainfall. We used a simulation heatwave event in controlled temperature cabinets and investigated effects of the different treatments on four stress indicators: leaf senescence, leaf water content, photosynthetic efficiency and the relative expression of two heat shock proteins, Hsp70 and smHsp17.6. Leaf senescence was significantly greater under the combined stress treatment, while declines in leaf water content and photosynthetic efficiency were much larger for C3 than C4 plants, particularly under the combined stress treatment. Species showed an increase in expression of Hsp70 associated with heat treatment, rather than drought stress. In contrast Hsp17.6 was only detected in two species, responding to heat rather than drought, although species' responses were variable. Overall, the C3 species were less tolerant than C4 species. Variation in individual plants within species was evident, especially under multiple stresses, and indicates that losses of individual plants may occur during a heat wave associated with this variability in tolerance. Heat waves will impose significant stress on plant communities that would not otherwise occur when heat and drought stress are experienced singly. Using ecologically relevant heat stress is likely to yield better predictability of how native plants will cope under a hotter, drier future.
未来，热浪（高热和低水分可用性）的强度预计将成为对生物最重要的影响之一。我们使用来自澳大利亚东部的六种本地草，评估了它们在低水分可用性下耐受热浪的能力。我们有兴趣了解不同光合途径的本地草在与低降雨量相关的生态相关夏季热浪下的生理和一些分子参数方面的差异响应。我们使用控制温度箱中的模拟热浪事件，研究了不同处理对四个应激指标的影响：叶片衰老、叶片水分含量、光合作用效率和两种热休克蛋白 Hsp70 和 smHsp17.6 的相对表达。在联合胁迫处理下，叶片衰老显著增加，而 C3 植物的叶片水分含量和光合作用效率下降幅度远大于 C4 植物，尤其是在联合胁迫处理下。与干旱胁迫相比，物种表现出与热处理相关的 Hsp70 表达增加。相比之下，Hsp17.6 仅在两种物种中检测到，对热而不是干旱有反应，尽管物种的反应是可变的。总体而言，C3 物种的耐受性低于 C4 物种。在单个物种内的个别植物中存在明显的变异性，尤其是在多种胁迫下，这表明在与这种变异性相关的热浪期间，个别植物可能会发生损失。热浪将对植物群落造成重大压力，如果不单独经历热和干旱胁迫，这些压力通常不会发生。使用生态相关的热应激很可能更好地预测在更热、更干燥的未来条件下本地植物将如何应对。
