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资助项目
6 could use lots of photosynthates, but contributed little to the accumulation of biomass. 4. Photosynthetic rate of P. armeniacum decreased a little at the noon, and the highest photosynthetic rate was observed at 10:00h in the greenhouse. The variation of photosynthetic rate was in the same trend as stomatal conductance. Higher relative humidity seemed to be the key for higher photosynthetic rate in P. armeniacum. 5. The photosynthetic capacity of C. flavum was statistically larger than that of P. armeniacum. The lower leaf photosynthetic capacity of P. armeniacum was related to its lower leaf nitrogen concentration,leaf phosphorus concentration and enzyme activities. Meanwhile, the extremely lower stomatal conductance and internal mesophyll conductance might greatly limit the photosynthetic capacity of P. armeniacum. The lower stomatal conductance and photosynthetic rate of Paphiopedilum might partially caused by the lack of chloroplasts in the guard cell of Paphiopedilum. Compared with C. flavum, P. armeniacum was more fond of shade environment.6. The short longevity leaf of Cypripedium had bigger photosynthetic capacity and greater potential for fast growth. But the longer LL of Paphiopedilum enhanced nutrient conservation which could compensate its lower photosynthetic capacity. The short longevity leaf of Cypripedium usually had higher photosynthetic rate per unit leaf mass and dark respiration rate, and photosynthetic capacity decreased fast with leaf age. However, for Paphiopedilum, the situation was the opposite. 7. Compared with Cypripedium, Paphiopedilum had higher water use efficiency and lower photosynthetic nitrogen use efficiency. 8. The leaf of Paphiopedilum had higher leaf construction cost and longer repayment time than that of Cypripedium. The leaf structures and physiological functions of Paphiopedilum and Cypripedium reflected the adaptation to their habitats. The leaf morphological and physiological evolution of Paphiopedilum was related to water and resource-conserving traits in the karst habitat. The leaf traits of Cypripedium were the adaptation to the environment rich in water and nutrients but easy to change with seasons.Our results provided evidence of divergent evolution of congeneric orchids under natural 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