Effects of Lead Stress on the Chlorophyll Content and Photosynthetic Fluorescence Characteristics of Vallisneria Natans

Abstract

In order to reveal the effects of lead stress on the chlorophyll content and fluorescence characteristics of Vallisneria natans, six Pb concentration levels were applied to a culture in clean river sand and water. The results showed that Pb could promote the synthesis of chlorophyll at a low concentration (Pb ≤ 10 mg•L -1 ) in one day. V. natans had certain tolerance to the stress of low Pb concentration. With the prolongation of stress time and increasing Pb concentration, the leaves of V. natans gradually lost their green color. Chlorophyll a decreased more than chlorophyll b. It had the least effect on carotenoids. Fv/Fm, Fv/Fo, qP, Y(II) and ETR decreased significantly (Pb > 10mg•L -1 ) in seven days. However, qN, Y(NO) and Y(NPQ) showed an upward trend. The efficiency of the leaves using light energy decreased noticeably, and the electron transport of PSII was blocked severely. It can be speculated that V. natans may be used in the phytoremediation of waters contaminated by a low concentration of lead.

Effects of high metal concentrations on antioxidative system in Phragmites australis grown in mine and flotation tailings ponds

“…On contrary, when only Pb was present in excess (Bor1, Rudnik) elevated CAT and APX activities were detected as an adaptive response to elevated ROS production by Pb metal ions, as already reported in Wolffia arrhiza, Lolium perenne and Eichhornia crassipes exposed to low Pb concentrations (Li and Luo 2012;Malar et al 2014;Piotrowska et al 2009). The same plants showed significant increase in Chl a and Chl b content, pointing to the possible promoting effect of low Pb concentration on their synthesis, as reported in several plant species (Gao et al 2019;Kumar and Prasad 2015). Whereas the decline in POD and GR activities in roots were provoked by high metal concentrations, their activities in leaves under the low metal content showed opposite patterns.…”