Key Laboratory of Tropical Plant Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yunnan 650223, China.
Physiol Plant. 2011 Jun;142(2):118-27. doi: 10.1111/j.1399-3054.2011.01448.x. Epub 2011 Apr 6.
Paphiopedilum and Cypripedium are close relatives in the subfamily Cypripedioideae. Cypripedium leaves contain guard cell chloroplasts, whereas Paphiopedilum do not. It is unclear whether the lack of guard cell chloroplasts affects photosynthetic induction, which is important for understory plants to utilize sunflecks. To understand the role of guard cell chloroplasts in photosynthetic induction of Paphiopedilum and Cypripedium, the stomatal anatomy and photosynthetic induction of Paphiopedilum armeniacum and Cypripedium flavum were investigated at different ratios of red to blue light. The highest stomatal opening and photosynthesis of intact leaves in P. armeniacum were induced by irradiance enriched with blue light. Its stomatal opening could be induced by red light 250 µmol m⁻² s⁻¹, but the magnitude of stomatal opening was lower than those at the other light qualities. However, the stomatal opening and photosynthesis of C. flavum were highly induced by mixed blue and red light rather than pure blue or red light. The two orchid species did not differ in stomatal density, but P. armeniacum had smaller stomatal size than C. flavum. The stomata of P. armeniacum were slightly sunken into the leaf epidermis, while C. flavum protruded above the leaf surface. The slower photosynthetic induction and lower photosynthetic rate of P. armeniacum than C. flavum were linked to the lack of guard cell chloroplasts and specific stomatal structure, which reflected an adaptation of Paphiopedilum to periodic water deficiency in limestone habitats. These results provide evidence for the morphological and physiological evolution of stomata relation for water conservation under natural selection.
杓兰属和兜兰属是杓兰亚科的近亲。兜兰属的叶子含有保卫细胞叶绿体，而杓兰属则没有。目前尚不清楚缺乏保卫细胞叶绿体是否会影响光合作用的诱导，这对林下植物利用光斑很重要。为了了解保卫细胞叶绿体在杓兰属和兜兰属光合作用诱导中的作用，研究了杏黄兜兰和黄花兜兰在不同红蓝光比例下的气孔解剖结构和光合作用诱导。完整叶片的气孔开度和光合作用在富含蓝光的光照下达到最大值，其气孔开度可以被红光 250 μmol m⁻² s⁻¹ 诱导，但气孔开度低于其他光质。然而，黄花兜兰的气孔开度和光合作用对蓝红光混合光高度诱导，而不是纯蓝光或红光。这两个兰科物种的气孔密度没有差异，但杏黄兜兰的气孔尺寸小于黄花兜兰。杏黄兜兰的气孔略微凹陷到叶片表皮中，而黄花兜兰则突出于叶片表面。杏黄兜兰的光合作用诱导较慢，光合速率低于黄花兜兰，这与缺乏保卫细胞叶绿体和特定的气孔结构有关，这反映了杓兰属对石灰岩栖息地周期性水分不足的适应。这些结果为自然选择下气孔结构与水分保存的形态和生理进化提供了证据。
