Uptake and Some Physiological Effects of Mercury in the Water Hyacinth, Eichhornia crassipes Solm.

Abstract

The study investigated the absorption and some physiological effects of mercury in water hyacinth (Eichhornia crassipes) plants found in Laguna de Bay. Plants of approximately similar size and vigor were collected from natural populations in the lake for the experiments. To which was added 1.0, 10.0, 20.0 and 50.0 ppm of the heavy metal for six days. Analysis of the mercury content of submerged and aerial tissues of the plant was done on the second, fourth and sixth day. Submerged tissues consistenly accumulated more of the heavy metal than the aerial tissues. The higher the level of mercury in the growth medium, the higher was the concentration of the heavy metal in the plant tissue. The physiological responses of the water hyacinth plant to various levels of mercury in the culture solution was determined in terms of gain in plant fresh weight, root growth, leaf development and chlorophyll content, ramet production and visible leaf injury symptoms. The addition of mercury caused a decrease in fresh water and an inhibited root growth and ramet production. The higher the level of mercury in the culture medium, the greater was the degree of growht inhibition. Leaf development, however, was not greatly affected by mercury. The addition of 0.005 and 0.005 and 0.01 ppH Hg. THe chlorophyll content of the mature leaves of plants that grow under 1.0 2.0 ppm Hg was greatly reduced. Visible leaf injury in terms of drying tips and necrotic spots was noted in plants grown in culture solution cotaining various levels of mercury. The higher the concentration of mercury, the greater was the degree injury.