不同光环境下烟草光合特性及同化产物的积累与分配机制

为了解烟草光合特性与光合作用同化产物的积累与分配对不同光环境的适应,以盆栽烟草为试验对象,于人工气候室中设置3种光照强度遮阴(400±15)～(500±15) μmol·m^-2·s^-1;自然光强:(800±15)～(1000±15) μmol·m^-2·s^-1;高光强:(1500±15)～(1800±15) μmol·m^-2·s^-1]系统研究光照条件对烟草光合特性及光合作用同化产物在烟株-土壤系统分配的影响.结果表明: 随着光照强度的降低,烟草各组分生物量逐渐减小,根冠比降低.净光合速率(P_n)、气孔导度(g_s)、蒸腾速率(T_r)均随光照强度的减弱呈下降趋势,胞间CO₂浓度(C_i)升高;在强光条件下烟草最大净光合速率(A_max)、光饱和点(LSP)、光补偿点(LCP)、暗呼吸速率(R_d)均达到最大值,弱光条件则具有较大的表观量子效率.光照强度影响烟草对¹³C的吸收、积累与分配,弱光条件下,烟草富集的¹³C进入到根部的比例明显较少,更多的分配到地上部.由此可知,外界光环境的变化不仅显著影响烟草叶片的光合特性与生物量积累,也使光合碳在烟株-土壤系统的分配格局发生变化.

Response of photosynthetic characteristics and accumulation and distribution of assimilation products in tobacco to different light environments

In order to reveal the photosynthetic characteristics and the mechanism about accumulation and distribution of photosynthetic assimilation products under different light environments, potted tobacco was cultivated in a climate control chamber, there were three light intensity treatments (shading: (400±15)-(500±15) μmol·m^-2·s^-1; natural light: (800±15)-(1000±15) μmol·m^-2·s^-1; high light: (1500±15)-(1800±15) μmol·m^-2·s^-1). The results showed that with the decrease of light intensity, the biomass and root allocation, the net photosynthetic rate (P_n), stomata conductance (g_s) and transpiration rate (T_r) were decreased, but the intercellular CO₂ concentration (C_i) increased. The maximum net photosynthetic rate (A_max), light saturation point (LSP), light saturation point (LCP) and dark respiration rate (R_d) reached the maximum level under high light condition while the apparent quantum efficiency was higher in low light environment. The effects of light intensity on the absorption, accumulation and distribution of ¹³C in tobacco were significant, with a reduced proportion of enriched ¹³C distributed to the root under shading. The changes in the external light environment not only significantly affected the photosynthetic cha-racteristics and biomass accumulation of tobacco leaves, but also the distribution pattern of photosynthetic carbon in tobacco plant-soil system.