| The experiment was carried out by the materials of both of Coreopsis lanceolata and Gaillardia pulchella for which was treated by the method of pot cultivation and water training respectively in this paper. The two species of Compositae were treated by lead stress,and their growth index, osmotic adjustment system, antioxidant enzyme systems and physiological characteristics and the change of absorbing Pb and other metal ions were measured, the results were as follows:1. Effects of different proportions of Pb tailings and garden soil on the physiological index of two species of Compositae.The effects of different mixed ratio of garden soil and Pb tailings on seedling growth and physiology indicators of Coreopsis and Gaillardia were studied by pot culture. The results showed that the chlorophyll a (Chla), chlorophyll b (Chlb) and carotenoid (Cx.c) contents of Coreopsis and Gaillardia increased first and then decreased, Coreopsis in1/4Pb tailings stress treatment reached the maximum (P<0.05). With the increase of Pb tailings content, chlorophyll contents of the two plant seedlings decreased. At higher stress levels and high levels of Pb tailings, relative conductivity values of Coreopsis and Gaillardia were significantly higher than the control increments; SOD and POD activities of Coreopsis significantly decreased, while, the SOD and POD activities of Gaillardia increased as Pb tailings content incremented. the results indicated that the tolerant ability of Gaillardia to Pb tailings stress was higher than Coreopsis. When the Pb tailings level exceeded a certain range and increasing stress time, SOD and POD plants begin to decline. It indicated that high concentrations of Pb tailings impact on the antioxidant system of plants, cell membrane damage, and increase in reactive oxygen species, along with the toxic effects of heavy metals appear. In this study, the Pro contents of Coreopsis and shoots Gaillardia were lower than that of control, while, the Pro content in the underground part of Gaillardia in1/4Pb tailings increased by10.8%and was significantly higher than the control.2. Effects of different levels of Pb tailings on seedling growth, Pb and other metal ions accumulation of Coreopsis and Gaillardia.Effects of different levels of Pb tailings on the seedling growth, Pb and other metal ions accumulation in Coreopsis and Gaillardia were studied by pot culture. The results showed that the relative growth rate of plants at low levels of Pb tailings stress was promoted. However, plant growth potential began to decline with the increasing levels of Pb tailings. The absolute most Pb accumulated in the roots of plants. correlation coefficient of Pb uptake between ground and underground parts of Coreopsis, Gaillardia were0.844**and0.926**respectively. The results show that Zn2+, Cd2+accumulation in shoot of Coreopsis and Gaillardia under Pb tailings stress was more significant, significantly higher than Cu2+, Na+, Ca2+, K+,in aboveground enrichment. However, Ca+, K+contents of Coreopsis and Gaillardia showed a downward trend, and generally lower than the control. Pb2+, Cd2+, Cu2+accumulation in Coreopsis slightly higher than that of Gaillardia, and Zn2+, Na+, K+contents of Gaillardia were slightly higher than Coreopsis. Both species of Compositae have a certain metals enrichment capability, while, the viability of Gaillardia was higher than Coreopsis according to the overall growth potential impact.3. Effects of Pb tress on stress-physiological of two species of Compositae in liquid culture.The effects of Pb tress on the growth and physiological parameters of Coreopsis and Gaillardia were sudied by liquid culture. In this study, low concentrations of Pb stress could promote photosynthesis, chlorophyll content, and high concentrations of Pb stress inhibited the growth, also inhibited Coreopsis and Gaillardia chlorophyll a, b and carotenoids generation. With the increase of Pb level and stress time, the amount of cells relative conductivity increased and SOD, POD activities of Coreopsis showed a trend of incresed first and then decline. SOD activity in the shoots of Gaillardia at120mg/L Pb treatment was maximum and97.5%higher than control (P<0.05). With Pb concentration increased, the malondialdehyde (MDA) show the upward trend. Pro content in Coreopsis seedling was lower than the control. The proline contents of Gaillardia seedlings shoot at60mg/LPb concentrations was higher than control and the highest level Pro content in underground appeared at120mg/LPb treatment. The results indicated that the ability of Gaillardia for Pb tailings remediation was stronger than Coreopsis did.4. The effects of Pb stress on seedlings growth, lead and other metal ions accumulation of Coreopsis and Gaillardia.The effects of Pb stress in different concentrations on seedlings growth, Pb and other metal ions accumulation of Coreopsis and Gaillardia were studied by liquid culture. The growth potentials of Coreopsis and Gaillardia were increased first and then decreased, which means that at low levels of Pb treatment was able to promote the growth and development of plants. Under higher Pb treatment, Coreopsis downward trend was more obvious, and Gaillardia was relatively slow, indicating high Pb stress was greater toxic effects on Coreopsis. The results show that both plant roots accumulated higher Pb than shoots, and significantly increased as the Pb concentration raised. Pb could promote Ca2+, Na+absorption of Coreopsis and Gaillardia, the translocation factors of these two Compositae species for Ca2+, Na+from roots to shoots were higher than that of control. Coreopsis enriched with Cu2+, K+. Cu2+content in the underground part of Gaillardia under30mg/LPb stress was35.6%lower than the control and K contents under90mg/LPb stress reached the peak and was higher by38.1%compared to the control, and then gradually decreased, which indicated a high concentration of Cu2+and Pb2+could inhibit K+absorption. Pb stress could promote Cu2+, K+and Na+translocation of Coreopsis and Pb2+, Ca2+, K+and Na+translocation of Gaillardia. The results indicated that Coreopsis and Gaillardia have different metal accumulation effect. |
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