Leaf anatomical structures of Paphiopedilum and Cypripedium and their adaptive significance.
Paphiopedilum and Cypripedium are closely related in phylogeny, but have contrasting leaf traits and habitats. To understand the divergence in leaf traits of Paphiopedilum and Cypripedium and their adaptive significance, we analyzed the leaf anatomical structures, leaf dry mass per area (LMA), leaf lifespan (LL), leaf nitrogen concentration (N (mass)), leaf phosphorus concentration (P (mass)), mass-based light-saturated photosynthetic rate (A (mass)), water use efficiency (WUE), photosynthetic nitrogen use efficiency (PNUE) and leaf construction cost (CC) for six species. Compared with Cypripedium, Paphiopedilum was characterized by drought tolerance derived from its leaf anatomical structures, including fleshy leaves, thick surface cuticles, huge adaxial epidermis cells, lower total stoma area, and sunken stomata. The special leaf structures of Paphiopedilum were accompanied by longer LL; higher LMA, WUE, and CC; and lower N (mass), P (mass), A (mass), and PNUE compared with Cypripedium. Leaf traits in Paphiopedilum helped it adapt to arid and nutrient-poor karst habitats. However, the leaf traits of Cypripedium reflect adaptations to an environment characterized by rich soil, abundant soil water, and significant seasonal fluctuations in temperature and precipitation. The present results contribute to our understanding of the divergent adaptation of leaf traits in slipper orchids, which is beneficial for the conservation of endangered orchids.
Guan
Zhi-Jie
ZJ
Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.
Zhang
Shi-Bao
SB
Guan
Kai-Yun
KY
Li
Shu-Yun
SY
Hu
Hong
H
D000222:Adaptation, Physiological; D029595:Orchidaceae / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure; D010788:Photosynthesis; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure; D054046:Plant Stomata / Q000648:ultrastructure