Plant distribution can be reflected by physiological responses to salinity of three submerged macrophytes from the Modern Yellow River Delta

Abstract

With 4 figures Abstract: Patterns of distribution vary greatly among species in the Modern Yellow River Delta, the largest es- tuarine wetland in China. Although salinity has been considered as the key factor determining plant distribution patterns in this delta, the intrinsic mechanisms accounting for distribution patterns are far from clear. To this end, three submerged macrophytes (Ceratophyllum demersum L., Potamogeton perfoliatus L. and Myriophyllum spica- tum L.) were grown in 0.2 (control), 1.2, 2.4 and 3.6 psu salinity waters. The relative growth rate (RGR), content of MDA (malondialdehyde) and activities of the enzymes (SOD - superoxide; POD - peroxidase; CAT - catalase; APX - ascorbate peroxidase) in leaves were investigated. The RGR of M. spicatum decreased only in the 3.6 psu treatment, while those of C. demersum and P. perfoliatus declined significantly with increasing salinity. Compared to the control, RGR of M. spicatum, C. demersum and P. perfoliatus decreased by 31.8 %, 78.5 % and 71.0 % while the MDA content increased by 12.0 %, 35.9 % and 28.3 % in the 3.6 psu treatment, respectively, indicating that M. spicatum had a higher salinity tolerance ability than the other two species. The activities of four antioxidative enzymes increased with increasing salinity in M. spicatum. However, for C. demersum and P. perfoliatus, the four antioxidative enzymes increased in the 0.2 to 2.4 psu treatments, but decreased subsequently in the 3.6 psu treat- ment except for the activities of SOD and APX in C. demersum. It is concluded that antioxidative enzymes can protect M. spicatum from oxidative stress under higher salinity, but that this mechanism is absent in C. demersum and P. perfoliatus.