Abstract:Olive (Olea europaea L.) is one of the four famous woody oil species across the world with important nutritional and pharmaceutical values. In order to reveal the relationship between drought resistance and photosynthesis characteristics, we conducted pot experiments to investigate the effect of drought stress on the photosynthetic characteristics of seven introduced olive varieties including Picholine, Picual, Manzanillo, Koroneiki, Frantoio, Arbequina and Coratina, which had been filtered the suitable for growth in the semiarid region of the Southwest of Sichuan Province. The results showed that: (1) the leaf relative water content (LRWC) of all the tested olive varieties was significantly reduced with the intensification of the degree of drought stress (P<0.05); At the later period of stress (25 days), the cultivars showed different levels of wilting symptom compared to control. Among them, Coratina showed the highest water loss rate while Manzanillo slightly affected, indicting the Manzanillo leaves exhibited a higher water retaining capacity compared to other cultivars under drought stress. (2) The concentrations of photosynthetic pigment in all the tested olive varieties were significantly decreased with the increasing duration of drought stress (P<0.05), which was mainly resulted from the rapid degradation of chlorophyll than biosynthesis; the Chla and Chlb contents in Arbequina, as well as Car content in Picholine were significantly declined after 25 d drought stress (P<0.05), while the Chla content of Manzanillo was not decreased obviously (P>0.05). (3) The photosynthetic parameters of the cultivars varied in response to drought stress. Net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) in leaves decreased, while the water use efficiency (WUE) increased with the drought. In addition, the drop of Pn, Tr and Ci of Frantoio and Gs of Picholine were higher than those of other varieties, while slightly decreased in Pn, Gs and Ci and sharply increased in WUE was observed in Manzanillo. Our research showed that under the persistent drought stress the olive seedling leaves were substantial loss of water and the photosynthetic pigment structure was destroyed and decomposed, as well as stomatals closed and photosynthesis decreased. Among the tested olive varieties, Manzanillo shows excellent adaptability to drought stress and is suitable for planting in the semiarid region of the Southwest of Sichuan Province.