Abstract: By using a modified model of lightresponse curve of plant photosynthesis, this paper studied the effects of different concentration CO₂ (380 and 600 umol·mol^-1) on the variations of quantum yield in the vicinity of light compensation point and the Kok effect of Koelreuteria paniculata  and Capsicum annuum L. The modified model fitted well the lightresponse curves of the photosynthesis of K. paniculata and C. annuum at 380 and 600 umol·mol^-1 of CO₂, and the photosynthetic parameters estimated by the modified model were in very close agreement with the measured data. The initial slope of the curve (φ₀) was greater than the quantum yield in the light compensation point of K. paniculata and C. annuum, and the quantum yield in the vicinity of the light compensation point was not a constant, and did not relate with dark respiration rate. Moreover, C. annuum at 380 and 600 umol·mol^-1 of CO₂ did not exist Kok effect. CO₂ concentration affected the Kok effect of K. paniculata but less affected the Kok effect of C. annuum. It was considered that the variation of the quantum yield in the vicinity of light compensation point of K. paniculata was come from the nonlinear response of the net photosynthesis rate to irradiance, but the Kok effect was not existed for C. annuum.

Key words: Qinghai Lake Wetland, final ecosystem services, beneficiaries, direct contribution.