An Yi-Dong, Roddy Adam B, Zhang Tian-Hao, Jiang Guo-Feng
Guangxi Key Laboratory of Forest Ecology and Conservation, Guangxi Colleges and Universities Key Laboratory for Cultivation and Utilization of Subtropical Forest Plantation, and State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry, Guangxi University, Nanning, Guangxi, China.
Institute of Environment, Department of Biological Sciences, Florida International University, Miami, FL, United States.
Front Plant Sci. 2023 May 31;14:1130724. doi: 10.3389/fpls.2023.1130724. eCollection 2023.
Flowers are critical for successful reproduction and have been a major axis of diversification among angiosperms. As the frequency and severity of droughts are increasing globally, maintaining water balance of flowers is crucial for food security and other ecosystem services that rely on flowering. Yet remarkably little is known about the hydraulic strategies of flowers. We characterized hydraulic strategies of leaves and flowers of ten species by combining anatomical observations using light and scanning electron microscopy with measurements of hydraulic physiology (minimum diffusive conductance ( ) and pressure-volume (PV) curves parameters). We predicted that flowers would exhibit higher and higher hydraulic capacitance than leaves, which would be associated with differences in intervessel pit traits because of their different hydraulic strategies. We found that, compared to leaves, flowers exhibited: 1) higher , which was associated with higher hydraulic capacitance ( ); 2) lower variation in intervessel pit traits and differences in pit membrane area and pit aperture shape; and 3) independent coordination between intervessel pit traits and other anatomical and physiological traits; 4) independent evolution of most traits in flowers and leaves, resulting in 5) large differences in the regions of multivariate trait space occupied by flowers and leaves. Furthermore, across organs intervessel pit trait variation was orthogonal to variation in other anatomical and physiological traits, suggesting that pit traits represent an independent axis of variation that have as yet been unquantified in flowers. These results suggest that flowers, employ a drought-avoidant strategy of maintaining high capacitance that compensates for their higher to prevent excessive declines in water potentials. This drought-avoidant strategy may have relaxed selection on intervessel pit traits and allowed them to vary independently from other anatomical and physiological traits. Furthermore, the independent evolution of floral and foliar anatomical and physiological traits highlights their modular development despite being borne from the same apical meristem.
花朵对于成功繁殖至关重要，并且一直是被子植物多样化的一个主要方面。随着全球干旱频率和严重程度的增加，维持花朵的水分平衡对于粮食安全和其他依赖开花的生态系统服务至关重要。然而，关于花朵的水力策略，人们所知甚少。我们通过将光学和扫描电子显微镜的解剖学观察与水力生理学测量（最小扩散导度（ ）和压力 - 容积（PV）曲线参数）相结合，对十个物种的叶片和花朵的水力策略进行了表征。我们预测花朵将表现出比叶片更高的 和更高的水力电容，这将由于它们不同的水力策略而与导管间纹孔特征的差异相关。我们发现，与叶片相比，花朵表现出：1）更高的 ，这与更高的水力电容（ ）相关；2）导管间纹孔特征的变化较小，以及纹孔膜面积和纹孔孔径形状的差异；3）导管间纹孔特征与其他解剖学和生理学特征之间的独立协调；4）花朵和叶片中大多数特征的独立进化，导致5）花朵和叶片在多变量性状空间区域上的巨大差异。此外，在不同器官中，导管间纹孔特征的变化与其他解剖学和生理学特征的变化是正交的，这表明纹孔特征代表了一个尚未在花朵中量化的独立变异轴。这些结果表明，花朵采用了一种避免干旱的策略，即维持高电容以补偿其较高的 ，以防止水势过度下降。这种避免干旱的策略可能放宽了对导管间纹孔特征的选择，并允许它们与其他解剖学和生理学特征独立变化。此外，花和叶的解剖学和生理学特征的独立进化突出了它们尽管源自相同的顶端分生组织但仍具有模块化发育。
