Objective: To compare the photosynthetic characteristics of Notopterygium incisum and N. forbesii in order to provide basic data for introduction and cultivation of the two wild medicinal species.
Method: The light-response, CO2-response and Chlorophy II fluorescence parameters of leaves at the booting stages between N. incisum and N. forbesii, were analyzed in situ by Li-6400 Portable Photosynthesis system under natural conditions.
Result: 1) The light saturation point (LSP) was 1539 micromol x m(-2) x s(-1) for N. incisum and 1464 micromol x m(-2) x s(-1) for N. forbesii, the maximum net photosynthetic rate (Pmax) was 22.95 micromol x m(-2) x s(-1) for N. incisum and 19.65 micromol x m(-2) x s(-1) for N. forbesii, the apparent quantum yield (AQY) was 0.0509 for N. incisum and 0.0470 for N. forbesii, LSP, AQY and Pmax of N. incisum were significantly higher than those of N. forbesii; the light compensation point (LCP) was 17.92 micromol x m(-2) x s(-1) for N. incisum and 26.69 micromol x m(-2) x s(-1) for N. forbesii, LCP of N. incisum was significantly lower than that of N. forbesii. 2) The carbondioxide compensation point (CCP) were 33.41 micromol x mol(-1) for N. incisum and 37.82 micromol x mol(-1) for N. forbesii, the carbon dioxide saturation point (CSP) were 988 micromol x mol(-1) for N. incisum and 1150 micromol x mol(-1) for N. forbesii, CCP and CSP of N. incisum were significantly lower than N. forbesii; the carboxylation efficiency (CE) were 0.0591 for N. incisum and 0.0459 for N. forbesii; the maximum rate of RuBP regeneration (Jmax) were 28.18 micromol x m(-2) x s(-1) for N. incisum and 25.32 micromol x m(-2) x s(-1) for N. forbesii; the light respiration rate (Rd) were 1.971 micromol x m(-2) x s(-1) for N. incisum and 1.736 micromol x m(-2) x s(-1) for N. forbesii, CE, Jmax and Rd of N. incisum were higher than those of N. forbesii. 3) The primary light energy conversion of PS II (Fv/Fm) was 0.8213 for N. incisum and 0.8257 for N. forbesii, wihich didn't showed significant difference, between N. incisum and N. forbesii there was no photoinhibition.
Conclusion: Both N. incisum and N. forbesii were C3 type plant, could perfectly acclimate to light condition. However, the weak light of N. incisum was absorbed significantly higher than that of N. forbesii, strong photosynthesis ability causes assimilation products accumulation of N. incisum obviously to be higher than that of N. forbesii.