Phytoremediation Of Pollution By Cadmium And Physiological Effects Of Cadmium On Plants

Plants can accumulate heavy metals form the environment. Phytoremediation of Cd polluted environment is an available method. Zizannia caduciflora and Acrous calamus were the accumulating plants of Cd. The accumulating abilities of different organs of Zizannia caduciflora and Acrous calamus were different. The main Cd accumulating organ of Zizannia caduciflora was its rhizome in which the highest concentration of Cd was 0.77 u g/g, and in shoot and root it was 0.06 and 0.36 u g/g. The main Cd accumulating organ of Acrous calamus was its shoot in which the concentration of Cd was 0.94 u g/g, and the organ with lowest Cd was rhizome in which the concentration of Cd was merely 0.17 u g/g. By comparing their accumulating abilities of Cd, Acrous calamus was superior to Zizannia caduciflora. Both of them could be used as remedying plants for Cd pollution.Cd was the unnecessary element of plants. The high concentration of Cd in environment was harmful for development and growth of plants. Effects of Cd on growth, photochmecal efficiency, chlorophyll content and net photosynthesis of Canna indica Linn and Rumex acetosa L were studied so that the theoretical basis of phytoremediation of pollution by Cd could be provided.Canna indica Linn was water cultured in 0, 0.4, 0.8, 1.6 and 3.2mgCd2+/L. During the whole experiment, the plants grew ordinarily, leaves were dark green and the root was white in control. The plants took on different toxic symptoms after the third day of exposed Cd. Then the toxic symptoms were more and more serious. The leaves of Canna indica Linn were yellow and its root little dark in 0.4mgCd2+/L. In 0.8, 1.6 and 3.2mg Cd2+/L, the growth of plant is held back obviously, and there were brown spots on the leaves which became more thinner than before and the root were dark. In control, the photochemical efficiency had no obvious change, but it declined seriously with Cd2+. In 3.2mg Cd2+/L, the content of chlorophyll was 0.43mg/gDW and the chlorophyll a/b was 1.2, which were only 0.70 mg/gDW and 2.4 in control. The content of chlorophyll b was not obviously different in different Cd concentration. The net photosynthesis of the plants also declined with Cd, which was 230.60 mgCO2/h ?cm2 in control, declined 15% ofcontrol in 3.2mgCd /L. Cd destroyed photosynthetic pigment, especially chlorophyll a and photosynthetic tissues, which then affected the photosynthetic efficiency and held back the growth of plants.In 0, 0.1, 0.2, 0.4 and l.Omg Cd2+/L, except the control, the leaves of Rumex acetosa L became thin, yellow and had brown spots after the fifth day with Cd. The toxic symptoms in 1.0mg Cd2+/L were most serious. In 0.1, 0.2 and 0.4mg Cd2+/L, the photochemical efficiency of plants were not obviously different, but in l.Omg Cd +/L, its photochemical efficiency was declined remarkably. In control, the content of chlorophyll was 1.282mg/g, chlorophyll a/b was3.44, but in l.Omg Cd2+/L, the chlorophyll content was 0.950mg/g, chlorophyll a/b was onlly2.45. The net photosynthesis was declined continuously with Cd2+.