The photosynthetic performance and related leaf traits of Incarvillea delavayi Bur. et Franch were studied at different water regimes to assess its capacity for photosynthetic acclimation to water stress. The initial response of I. delavayi to water stress was the closure of stomata, which resulted in down-regulation of photosynthesis. The stomatal limitation (S L ) represented the main component to photosynthetic limitations but non-stomatal limitation (NS L ) increased quickly with the increasing water stress, and had similar magnitude to S L under severe water stress (soil moisture 25 -30 % of field capacity). Chlorophyll (Chl) a fluorescence parameters characterizing photosystem (PS) 2 photochemical efficiency (Φ PS2 ), electron transport rate (J) and photochemical quenching (qP) decreased with the increasing water stress, indicating impaired photosynthetic apparatus. However, the water-stressed plants had a increased mesophyll CO 2 diffusional conductance, Chl a/b ratio, leaf nitrogen partitioning in RuBPCO and bioenergetics in later grown parts, indicating that I. delavay had a substantial physiological plasticity and showed a good tolerance to water stress.

Photosynthesis and leaf traits of five species in genus Cypripedium were compared in natural habitats and transplant nursery to develop effective strategy for cultivation and conservation. Among five species, C. guttatum had the highest photosynthetic capacity (P Nmax ) in the natural habitat and nursery, while C. lichiangense the lowest. The differences in P Nmax among species were correlated with leaf N content (LNC) and leaf dry mass per unit area (LMA). After transplanting from natural habitats to nursery, the P Nmax of C. lichiangense and C. yunnanense decreased, that of C. guttatum increased, while those of C. flavum and C. tibeticum remained relatively constant. The variations in LNC and biochemical efficiency would be responsible for the differences in P Nmax between plants in natural habitats and in the nursery, but not the relative stomatal limitation. After transplanting, the F v /F m of C. lichiangense and C. yunnanense were declined. Meanwhile, the temperature ranges maintaining 90 % P Nmax of C. lichiangense and C. yunnanense were narrower than those of the other three species. Thus the biochemical process in five species played a major role in the differences of P Nmax after transplanting, and the widespread species had higher photosynthetic adaptability than the narrow-spread species.