连作对烤烟生长特性和光合能力的影响

研究了连作2年和连作5年对烤烟(Nicotiana tabacum)的生长及叶片的光合特性的影响。结果表明，连作2年对烤烟的生长和光合影响不大，而连作5年却明显限制了烤烟叶片的生长，减弱了叶片的光合能力。连作5年显著降低了烤烟叶片的叶绿素含量，烤烟叶片的净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)下降，但胞间CO2浓度(Ci)却变化不大，同时连作5年的烤烟叶片的表观量子效率(AQY)、光饱和点(LSP)、光饱和时最大光合速率(Pmax)、羧化效率(CE)、CO2饱和点(CSP)和CO2饱和时最大光合速率(Jmax)均比正茬低，而光补偿点(LCP)和CO2补偿点(CCP)却增加。因此，连作明显降低了烤烟叶片对光强和CO2的利用能力，说明连作5年引起烤烟叶片光合作用减弱不仅仅是由气孔因素引起的，连作还限制了叶肉细胞对CO2的利用能力。

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.