| Photosynthetic characters in active leaves of potato under four different fertilizer levels were studied with Li-6400 portable photosynthesis in the semiarid areas of southern Ningxia. The results showed that, under the condition of soil water stress during the flowering stage of potato, the daily changes of net photosynthetic rate(Pn), transpiration rate(Tr) and stomatic conductance(Gs) were parabola type. The photosynthetic rate was enhanced under suitable fertilizer level (middle fertilizer), however, this effect depended on the supply status of soil moisture. Under low soil moisture condition, the effect of fertilizer on photosynthetic rate was not distinct. Under high fertilizer condition,the soil water was consumed largely during the early period,therefore,the crop suffered severe drought stress during the procreation stage, and the net photosynthetic rate(Pn), transpiration rate(Tr) and stomatic conductance(Gs) of potato declined greatly. |