The distribution of submerged macrophytes in response to intense solar radiation and salinity reveals hydrogen peroxide as an abiotic stress indicator

Abstract

Abstract The feasible condition for submerged macrophytes to grow is hard to understand as many environmental factors contribute to establish their distribution with different intensities. Hydrogen peroxide (H2O2) is one of reactive oxidative species (ROS) was investigated to assess the possibility as an indicator to evaluate the submerged macrophyte species distribution in a lake. Submerged macrophytes such as Potamogeton anguillanus was abundant in Lake Shinji. The biomass distributed largest at around 1.5m deep, under low solar radiation intensity, and no biomass was found in less than 0.3 m deep, where solar radiation was high. Diurnally, H2O2concentration of the tissues varied in response to the photosynthetic active radiation (PAR) intensity, which was followed by antioxidant activities, though slightly delayed. Laboratory experiments were conducted either with different PAR intensities or with different salinity concentration. The H2O2was stably maintained for 30days up to about 200mmol/m2/s of PAR, however, gradually increased with higher PAR. The H2O2concentration became higher with higher salinity. Chlorophyll a (Chl-a) concentration, changed associated with the changing H2O2 concentration, however, following a unique negative relationship with H2O2concentration. However, if H2O2 exceeded 45mmol/g FW, then the homeostasis collapsed, then H2O2 and Chl-a significantly declined afterwards. These results indicated the negative effect of H2O2on the physiological condition of the plant. The increase in H2O2concentration was prevented by antioxidant activities, which increased with increasing H2O2 concentration.