选择具有典型连作障碍效应的药用植物地黄(Rehmannia glutinosa)为试验材料, 以正茬地黄为对照, 研究连作条件下地黄植株的生理生态特性变化。结果表明, 该试验条件下地黄的连作障碍效应起始于苗期, 在栽种后60天时, 连作引起植株细胞膜质过氧化作用, 使膜的正常结构和功能受到损伤; 重茬地黄的光合速率(P_n)、气孔导度(G_s)和胞间CO₂浓度(C_i)显著低于对照, 而气孔限制值(L_S) 33.97%, 显著高于对照, 同期重茬地黄叶绿素含量(Chl)也开始显著低于对照。相关分析表明, P_n与G_s、Chl含量相关(相关系数分别为0.977和0.814)。对植株叶片叶肉细胞的电镜观察显示, 连作条件下地黄光合细胞结构在其生长中期开始发生变化。因此, 在地黄生长早期由于(连作)环境胁迫植株叶片细胞内活性氧、自由基积累所带来的膜结构损伤, 导致了叶绿素含量的降低, 而气孔关闭以及叶绿素含量的降低共同造成连作地黄早期光合能力降低, 生长受阻, 从而表现出明显的障碍效应。

Aims The Chinese medicinal plant Rehmannia glutinosa has a significant continuous cropping obstacle effect. Our objective was to determine its physio-ecological properties under continuous cropping.

Methods We determined changes in the physio-ecological properties of R. glutinosa under continuous cropping, with the first cropping plants used as the control.

Important findings The continuous cropping obstacle effect on R. glutinosa occurred at the seedling stage. The plasamembrane lipid peroxidation of the plants led to impaired structure and function of plant cells in the 60 days after being planted under continuous cropping. Also, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and chlorophyll content (Chl) of the plants under continuous cropping were significantly lower than those of the control, but the reverse was true for limited stomatal value (L_s). P_n was significantly correlated with G_s and Chl (r = 0.977 and 0.814, respectively). Electron microscopy revealed that changes in mesophyll cell ultrastructure, including chloroplast structure, began at the mid-growth stage under continuous cropping. Therefore, it was suggested that the accumulation of reactive oxygen species (ROS) and free radicals in plant cells, caused by the stressful condition of continuous cropping, resulted in damaged membrane structure, which in turn led to decreased chlorophyll content, closed stomata and reduced photosynthetic capacity and consequently retarded growth of the plants at the seedling stage, i.e., the so-called continuous cropping obstacle effect.