Abstract: Responses of photosynthetic parameters of current and 1-year-old Larix olgensis Herry., Larix kaempferi Carr. and Larix gmelinii Rupr. seedlings to light intensity,curves of diurnal variation and seasonal variation were studied,the results are as follows: ①Among the three plants,the diurnal variation of photosynthetic rate of current and 1-year-old Larix olgensis Herry. and Larix kaempferi Carr. seedlings and current Larix gmelinii Rupr. seedlings were found as a double-peak curve,which were featured with “Noon rest” but that of 1-year-old Larix gmelinii Rupr. seedlings presented a single peak curve. ②Larix kaempferi Carr. seedlings had the highest light saturation point (LSP) and Larix gmelinii Rupr. seedlings had the lowest light compensation point (LCP). ③All of the 1-year-old Larix seedlings appeared highest photosynthetic capacity in the middle growing stage. From the age,the photosynthetic capacity of current Larix seedlings were lower than that of 1-year-old seedlings in the first and middle growing stages,but higher in the late growing stage. ④From the species,the sequence of maximum net photosynthetic rate (P_max) of current and 1-year-old Larix seedlings was Larix kaempferi Carr.＞Larix gmelinii Rupr.＞Larix olgensis Herry. in the first growing stage; by the middle growing stage,the sequence of P_max of current Larix seedlings was the same to the first growing stage,but 1-year-old Larix seedlings were different as Larix olgensis Herry.＞Larix kaempferi Carr.＞Larix gmelinii Rupr.; turn to the late growing stage,the sequence of P_max of current Larix seedlings was Larix olgensis Herry.＞Larix gmelinii Rupr.＞Larix kaempferi Carr. and that of 1-year-old seedlings was in reverse with those in middle growing stage. We conclude that,there were different photosynthetic characteristics of the three species in the same growing stage; while the different photosynthetic characteristics of same species had also been showed in different ages and growing stages; among the three Larix species,the repair ability to the photoinhibition of Larix olgensis Herry. seedlings were strongest,that of Larix kaempferi Carr. seedlings took second place and Larix gmelinii Rupr. seedlings were weakest. Larix kaempferi Carr. seedlings were more photophilic and had strong photosynthetic capacity, which were not prone to photoinhibition,while Larix gmelinii Rupr. seedlings were more shade-tolerant. Therefore,we should consider the photosynthetic characteristics of different species to obtain optimal illumination conditions in cultivation and forestation.

Key words: Larix olgensis Herry., Larix kaempferi Carr., Larix gmelinii Rupr., photosynthesis, curve of diurnal variation