| Copper is one of the essential microelements for plants, which plays an important role in plant growthand development. But when the increase of copper content in environment such as in soil is higher than a certain value, the excessive copper can result in the poisoning effects on plants, which can interfere with normal physiological metabolism of plants and impact on plant growth, development and reproduction. Moreover, excessive copper can also lead to the decrease of agricultural production and product quality. Finally, copper can enter the body through food and endanger human health.In this paper, grapes test tube seedlings were used to determine effect of excessive exogenous Cu2+ on the growth and possible mechanism. The main results were follows:1,Under condition of Cu2+ Stress treatment (5mg/L ), all growth indexes of the grapes test tube seedlings are better than those of the controls. Thereby, it is further showed that copper ion is as the essential trace elements for plants at low concentrations. Copper ion functios probably as co-factor for many proteins. At the same time, copper ion in chloroplasts is the component of plastocyanin (PC) of electron transport chain involving in the photosynthesis and many other metabolism. However, when the copper ion concentration is higher than a certain threshold, the plants are stressed. In this experiment, 10 and 15 mg/L Cu2+ treatment inhibited the growth of the grapes test tube seedlings leading to the reduction of root number, root length compared to those of controls. 40 mg/L Cu2+ is the lethal concentration of grapes test tube seedlings.2,Different species of grapes test tube seedlings showed different tolerant to treatment of CuSO4. Among the selected five varieties, the HTE and MRZ are highly sensitive, and so they were not used for the further study; and three other species Chris (17), A27 and Lo Sand (LS) are more tolerant to copper stress, and Chris (17) is the highest tolerant.3,Compared with that of the controls, the chlorophyll content of the grapes test tube seedlings treated with 5mg / L Cu2+ increased and net photosynthetic rate also increased, suggesting that the copper possiblely taken part in the electron transport in the photosynthetic electron chain. However, when Cu2+ is higher than 10mg / L, chlorophyll content of the treated seedlings decreased, while the net photosynthetic rate also display the downward trend, and there is a negative correlation between net photosynthetic rate and the stress concentration. These results are consistent with previous research findings.4,Antioxidant responses of grapes test tube seedlings are different under condition of different concentrations of CuSO4 . The activity of CAT and POD are shown as trend in "the first increase then decline". In a certain range of treatment time, the leaf activity of the POD and CAT in the grapes test tube seedlings increased and also the content of MDA increased, which can be explained that at the initial stage of treatment of CuSO4 caused the accumualtion of ROS in stressed plants, and which stimulates the plants self-protection system for enhancing the activity of antioxidant enzymes. However, this self-protection system could not completely remove the excessive ROS. Therefore, both the MDA and plasma membrane permeability in the leaves of the grapes test tube seedlings increased. The result suggests that one of the ways of the Cu2+ toxicity is oxidative stress. |
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