Abstract：
OBJECTIVE: Light is essential for plants, and local populations exhibit adaptive photosynthetic traits depending on their habitats. Although plastic responses in morphological and/or physiological characteristics to different light intensities are well known, adaptive divergence with genetic variation remains to be explored. This study focused on Saxifraga fortunei (Saxifragaceae) growing in sun-exposed and shaded habitats.
METHODS: We measured the leaf anatomical structure and photosynthetic rate of plants grown in their natural habitats and in a common greenhouse (high- and low-intensity light experimental sites). To assess differences in ecophysiological tolerance to high-intensity light between the sun and shade types, we evaluated the level of photoinhibition of photosystem II and the leaf mortality rate under high-intensity light conditions. In addition, population genetic analysis was conducted to investigate phylogenetic origins.
RESULTS: Clear phenotypic differences were found between the sun and shade types despite their recent phylogenetic origin. The leaf anatomical structure and photosynthetic rate showed plastic changes in response to growing conditions. Moreover, the sun type had a well-developed palisade parenchyma and a higher photosynthetic rate, which were genetically fixed, and a lower level of photoinhibition under high-intensity light.
CONCLUSIONS: Our findings demonstrate that light intensity is a selective pressure that can rapidly promote phenotypic divergence between the sun and shade types. While phenotypic changes in multiple photosynthetic traits were plastic, genetic divergence in specific traits related to adaptation to high-intensity light would be fundamental for ecotypic divergence to different light regimes.
METHODS: We measured the leaf anatomical structure and photosynthetic rate of plants grown in their natural habitats and in a common greenhouse (high- and low-intensity light experimental sites). To assess differences in ecophysiological tolerance to high-intensity light between the sun and shade types, we evaluated the level of photoinhibition of photosystem II and the leaf mortality rate under high-intensity light conditions. In addition, population genetic analysis was conducted to investigate phylogenetic origins.
RESULTS: Clear phenotypic differences were found between the sun and shade types despite their recent phylogenetic origin. The leaf anatomical structure and photosynthetic rate showed plastic changes in response to growing conditions. Moreover, the sun type had a well-developed palisade parenchyma and a higher photosynthetic rate, which were genetically fixed, and a lower level of photoinhibition under high-intensity light.
CONCLUSIONS: Our findings demonstrate that light intensity is a selective pressure that can rapidly promote phenotypic divergence between the sun and shade types. While phenotypic changes in multiple photosynthetic traits were plastic, genetic divergence in specific traits related to adaptation to high-intensity light would be fundamental for ecotypic divergence to different light regimes.
摘要：
目的：光对植物来说是必不可少的，当地种群根据其栖息地表现出适应性光合特性。尽管对不同光强度的形态和/或生理特征的塑性响应是众所周知的，与遗传变异的适应性差异还有待探索。这项研究的重点是在阳光照射和阴暗的栖息地中生长的虎耳草（Saxifragaceae）。
方法：我们测量了在其自然栖息地和普通温室（高和低强度光实验地点）中生长的植物的叶片解剖结构和光合速率。为了评估阳光和阴影类型之间对高强度光的生态生理耐受性的差异，我们评估了在高强度光照条件下光系统II的光抑制水平和叶片死亡率。此外,进行了群体遗传分析以调查系统发育起源。
结果：尽管最近发生了系统发育，但在阳光和阴影类型之间发现了明显的表型差异。叶片解剖结构和光合速率显示出响应生长条件的塑性变化。此外，太阳型具有发育良好的栅栏薄壁组织和较高的光合速率，是基因固定的，以及在高强度光下较低水平的光抑制。
结论：我们的发现表明，光强度是一种选择性压力，可以迅速促进阳光和阴影类型之间的表型差异。虽然多个光合性状的表型变化是可塑的，与适应高强度光相关的特定性状的遗传差异对于不同光态的生态型差异是基础。
方法：我们测量了在其自然栖息地和普通温室（高和低强度光实验地点）中生长的植物的叶片解剖结构和光合速率。为了评估阳光和阴影类型之间对高强度光的生态生理耐受性的差异，我们评估了在高强度光照条件下光系统II的光抑制水平和叶片死亡率。此外,进行了群体遗传分析以调查系统发育起源。
结果：尽管最近发生了系统发育，但在阳光和阴影类型之间发现了明显的表型差异。叶片解剖结构和光合速率显示出响应生长条件的塑性变化。此外，太阳型具有发育良好的栅栏薄壁组织和较高的光合速率，是基因固定的，以及在高强度光下较低水平的光抑制。
结论：我们的发现表明，光强度是一种选择性压力，可以迅速促进阳光和阴影类型之间的表型差异。虽然多个光合性状的表型变化是可塑的，与适应高强度光相关的特定性状的遗传差异对于不同光态的生态型差异是基础。
