Effects of continuous cropping on plant growth and photosynthetic capacity in leaves of flue-cured tobacco

In this paper,plant growth and photosynthetic characteristics in leaves of flue-cured tobacco grown in continuous cropping soil for 2 and 5 years were investigated.The results showed that 2-years continuous cropping did not affect plant growth and photosynthetic characteristics in the leaves of flue-cured tobacco,but 5-years continuous cropping limited plant growth and photosynthetic capacity.The chlorophyll content in leaves of flue-cured tobacco grown in 5-years continuous cropping soil significantly reduced.The net photosynthetic rates(Pn),transpiration rate(Tr) and stomatal conductance(Gs) in leaves of flue-cured tobacco for 5-years continuous cropping decreased,but intercellular CO2 concentration(Ci) changed little.The apparent quantum yield(AQY),light saturation point(LSP),photosynthetic rate saturated light(Pmax),carbolyation efficiency(CE),CO2 saturation point(CSP) and photosynthetic rate at saturated CO2(Jmax) in leaves of tobacco decreased,and CO2 compensation point(CCP) and light compensation points(LCP) increased significantly for 5-years continuous cropping.It suggested that continuous cropping significantly decreased light and CO2 utilization in leaves of tobacco,and the decrease of photosynthetic capacity under 5-years continuous cropping was not only caused by stomatal factors,but also utilization ability of CO2 in mesophyll tissue.