chlorophyll-a and perchlorate

Perchlorate contamination in water is of concern because of uncertainties about toxicity and health effects, impact on ecosystems, and possible indirect exposure pathways to humans. Therefore, it is very important to investigate the ecotoxicology of perchlorate and to screen plant species for phytoremediation. Effects of perchlorate (20, 200, and 500 mg/L) on the growth of four wetland plants (Eichhornia crassipes, Acorus calamus L., Thalia dealbata, and Canna indica) as well as its accumulation in different plant tissues were investigated through water culture experiments. Twenty milligrams per liter of perchlorate had no significant effects on height, root length, aboveground part weight, root weight, and oxidizing power of roots of four plants, except A. calamus, and increasing concentrations of perchlorate showed that out of the four wetland plants, only A. calamus had a significant (p<0.05) dose-dependent decrease in these parameters. When treated with 500 mg/L perchlorate, these parameters and chlorophyll content in the leaf of plants showed significant decline contrasted to control groups, except the root length of E. crassipes and C. indica. The order of inhibition rates of perchlorate on root length, aboveground part weight and root weight, and oxidizing power of roots was: A. calamus > C. indica > T. dealbata > E. crassipes and on chlorophyll content in the leaf it was: A. calamus > T. dealbata > C. indica > E. crassipes. The higher the concentration of perchlorate used, the higher the amount of perchlorate accumulation in plants. Perchlorate accumulation in aboveground tissues was much higher than that in underground tissues and leaf was the main tissue for perchlorate accumulation. The order of perchlorate accumulation content and the bioconcentration factor in leaf of four plants was: E. crassipes > C. indica > T. dealbata > A. calamus. Therefore, E. crassipes might be an ideal plant with high tolerance ability and accumulation ability for constructing wetland to remediate high levels of perchlorate polluted water.

Topics: Acorus; Biodegradation, Environmental; Chlorophyll; Eichhornia; Lilium; Marantaceae; Perchlorates; Plant Leaves; Plant Roots; Plants; Risk Assessment; Water Pollutants, Chemical; Wetlands

Perchlorate is a new emerging persistent pollutant, while no studies about its effects on plants have been reported both home and abroad. In order to explore the effects of perchlorate on growth and physiology of aquatic plant, Alternanthera philoxeroides were treated by 1/20 Hoagland nutrient solution with different concentrations (0, 1, 5, 20, 100, 500 mg/L) of ClO4- under the controlled conditions. The results showed as follow. (1) Under perchlorate treatment, relative growth yield,dry weight of root,shoot and leaves were inhibited at different degrees, in which root biomass under different treatments showed significant difference to the control. After treatment for 40 d, relative growth yield of different treatments at concentration from 1 mg/L to 500 mg/L were about 61.6%, 60.8%, 53.1%, 20.4% and 3.3% separately of the control. And the order of variation coefficients of biomass in different organ were as follows: leaf > root biomass > stem; the relationship of biomass allocation in different organs of Alternanthera philoxeroides under perchlorate treatment changed, and the proportion of stem biomass increased,while leaf decreased, in which 100 and 500 mg/L ClO4- treatment showed significant difference to the control. (2) Under perchlorate treatment, young leaves of Alternanthera philoxeroides presented injury symptoms (such as parietal roiling reversely, leaf edge getting black and withered etc), and the damaged degree of Alternanthera philoxeroides increased with the increase of treatment concentration and time. (3) Under perchlorate treatment, the relative chlorophyll content (SPAD value), primary maximal PSII efficiency(Fv/Fm), efficiency of excitation capture by open PSII centre (F'v,/F'm), actual photochemical efficiency of PSII (phi(PS II)), electron transport rate (ETR), maximal electron transport rate(ETR ,) and other indexes were inhibited at different degrees. SPAD and chlorophyll fluorescence parameters (phi(PS II)) etc. could be used as sensitive physiological indexes to reflect the effects of perchlorate stress. The results suggest that perchlorate treatment can damage the photosynthetic system and leaf, decrease photochemical efficiency, and inhibit growth of Alternanthera philoxeroides. Leaf and root show a higher sensitivity to perchlorate,while stem with a lower sensitivity.

Topics: Amaranthaceae; Chlorophyll; Environmental Pollutants; Fluorescence; Perchlorates; Photosynthesis; Photosystem II Protein Complex