四种珍稀濒危石斛属植物光合特性及叶片显微结构的比较研究

his study was carried out to determine the daily change of net photosynthetic rate (Pn),light response curve, CO2 response curve, leaf chlorophyll content and leaf microstructure of fourDendrobium species, including D. scoriarum, D. lituiflorum, D. lohohense, and D. aduncum. Thepurpose of this investigation was to learn more about the photosynthetic characteristics ofDendrobium species. The results were as follows: (1) Dendrobium scoriarum and D. aduncum hadpositive Pn during the daytime, with the maximum peak at 8:00-10:00 a.m., and the nighttime Pnwas lower than that during the daytime, and there was positive Pn. Dendrobium lituiflorum andD. lohohense showed a bimodal curve of Pn during the daytime, with positive Pn during thedaytime and negative Pn during the nighttime. (2) Among the four species of Dendrobium,D. lituiflorum has the strongest photosynthetic capacity, while D. lohohense has the widest lightadaptation range. (3) The initial carboxylation efficiency (), potential maximum netphotosynthetic rate (Amax) and photorespiration rate (Rp) of D. lituiflorum were significantly(P<0.05) greater than those of the other three Dendrobium species. (4) The leaf thickness (LT) ofD. aduncum and D. scoriarum were greater than those of D. lituiflorum and D. lohohense, whilestomatal density (SD) showed an opposite trend. (5) The total chlorophyll content (Chl),chlorophyll a (Chla), and chlorophyll b (Chlb) of D. lituiflorum were significantly (P<0.05) higherthan those of the other three Dendrobium species. (6) The mesophyll thickness (MT) wassignificantly (P<0.05) negatively correlated with maximum net photosynthetic rate (Pmax); The SDwas highly significant (P<0.01) positively correlated with Pmax, and significantly (P<0.05)positively correlated with potential maximum net photosynthetic rate (Amax); total chlorophyllcontent (Chl) was significantly (P<0.05) positively correlated with Pmax and Amax. In conclusion,the four Dendrobium species may respond to low light levels, being affixed to tree trunks, orgrowing in stony, water-deficient settings by developing larger leaf pulp tissue and low stomataldensity. The four Dendrobium species' total chlorophyll concentration, stomatal density, and leafpulp thickness are significant determinants of their photosynthetic potential. For the fourDendrobium species to flourish during introduction and cultivation, it is helpful to establish aproper light environment and raise the CO2 content adequately. The findings of this research canserve as a foundation of reference for the introduction of agriculture and the preservation ofgenetic resources.