Responses of dry weight growth under SO2 stress in an SO2‐tolerant plant, Polygonum cuspidatum

Abstract

AbstractThe effects of exposure to 0.5–0.7 ppm SO2 for about one month on the dry weight growth and net photosynthesis of Polygonum cuspidatum were investigate. Furthermore, the carbon and nitrogen concentrations in each plant organ were measured. The results obtained showed no significant decrease in the total dry weight of SO2‐treated plants in comparison with controls. On the other hand, the leaf area (LA) and/or leaf dry weight of SO2‐treated plants were increased, and the root dry weight (RW) was decreased, in comparison with controls. The leaf carbon assimilation rate (CAR) in SO2‐treated plants was slightly decreased in spite of a clear decrease in net photosynthesis, and the value of (SW+RW)/LA (SW stem dry weight) was decreased in comparison with controls, thus minimizing the reduction in CAR. Furthermore, the ratio of total leaf carbon absorption (leaf area x CAR) to total root nitrogen absorption (root dry weight x nitrogen assimilation rate) in SO2‐treated plants was similar to that in controls. From these results, it can be concluded that an increase in leaf area and/or leaf dry weight and a decrease in root dry weight in P. cuspidatum under SO2 stress may be induced in order to compensate for the decrease in CAR and to maintain the ratio of total leaf carbon absorption to total root nitrogen absorption in the early stage of vegetative growth.