CO2, H2O exchange and stomatal regulation of regenerated Camptotheca acuminata plantlets during ex vitro acclimatization

摘要

For finding the changes in CO2, H2O exchange and their stomatal regulation during ex vitro acclimatization of regenerated Camptotheca acuminata plantlets, the net photosynthesis rate (Pn), respiration rate (Rd), light compensation point (Lc) and light saturation point (Ls), transpiration rate (Tr), stomatal conductance (gs) and water use efficiency(WUE) were measured during 37 days of ex vitro acclimatization. The results showed that Pn sharply increased until 29 days, then slightly decreased. A substantial decrease in Lc and a substantial increase of Ls in the former two weeks were observed, indicating the light regime enlargement for effective leaf photosynthesis. Tr and gs abruptly decreased during the first week then linearly increased until 29days ex vitro acclimatization, reflecting the strong regulation effect of stomata on water changes of ex vitro acclimating plantlets. Stomatal regulation effect on CO2 exchange was different from that on water exchange, i.e. Pn was almost independent of gs during the first week, while Pn was significantly correlated with gs thereafter (i.e. dual patterns). Different from dual patterns of gs-Pn relation, the Tr monotonously linearly increased with gs. Furthermore, WUE was almost independent on gs during the first week, while a marked decreasing tendency with gs was found thereafter. At the beginning of the acclimatization, WUE was mainly determined by photosynthetic capacity, while transpiration becomes a main determinant factor for WUE from 7 to 37 days’ acclimatization.