Abstract: By the ways of falling and airproofing, the research was made on the photosynthetic characters of grape (Vitis vinifera L. ‘Red Globe’) p lantlets in vitro cultivated under different temperatures and photosynthetic availability radiations ( PAR). The results showed that under the temperatures between 20 ℃ and 30 ℃, the dark resp iration rate (Rd ) rose with the rise of the temperature, while the net photosynthesis rate(Pn) reached the highest in 25℃, slowed in 30 ℃, and reduced to the lowest in 20 ℃. However, the compensation point of CO₂ was the lowest in 25 ℃, rose in 20 ℃, and reached the highest in 30 ℃. When the PAR was between 40 and 200μmol·m^-2 ·s^-1 , the P_n of the grape p lantlet rose with the increase of PAR,while the compensation point of CO₂ decreased with the increase of the PAR. When PAR was available, the concentration of CO₂ in the vessel reduced rap idly, almost close to the compensation point of CO₂. The insufficient supp ly of CO₂ is the chief factor that affects the assimilation of the plantlets. In the stage of indoor cultivation, the weak light, temperature changes by day and night and the imp rovement of the ventilation of the cultivated vessels are advantageous to imp roving the photosynthesis of the plantlets. And in the process of transplantation and domestication, the gradual increase and extension of the light are advantageous to accumulating the products of the plantlet assimilation and generating the strong plantlets.

Key words: grape, plantlet, photosynthetic character, temperature, PAR