Effect Of CoCl₂ On Photosynthetic And Physiological Characteristics Of Pepper Seedlings Under Low Temperature And Poor Light Stress

The research was grounded on the favorable effect of cobalt(Co) on plants and the actual situation of solar greenhouse in winter and spring under the combination of low temperature and poor light. ?Xiangyan No.16’ pepper seedlings were selected in this study to research the effect of 0.06mol/L concentration of Co Cl2 under the combined stress of the temperature 15℃/5℃(day/night) and light 100μmol·m-2·s-1, then the impact of cobalt elements on plants’ growth index, photosynthetic gas exchange parameters, chlorophyll fluorescence, antioxidant enzyme systems and cell membrane permeability were studied, in the hope of providing the theoretical basis and practical guidance for solar greenhouse pepper production in the northern winter and spring. The followings are the results we researched:1. The height, stem diameter, fresh and dry weight of root, fresh and dry weight of top, root shoot ratio and root activity of the seedlings all decreased under the combination of poor light and low temperature. After the treatment with Co Cl2 the growth indexs of pepper seedlings increased significantly.2. Chlorophyll concentration of pepper seedlings decreased significantly under the combination of poor light and low temperature. Net photosynthetic(Pn) rate and transpiration(Tr) rate also decreased, however intercellular CO2 concentration(Ci) increased. After the treatment with Co Cl2 the Pn and Tr has fallen much less and Ci has also decreased significantly. Increasing photosynthetic capacity of plants under the combined stress of poor light and low temperature and reducing the harm caused by the stress.3. Fv/Fm, ФPSⅡ, Fv’/Fm’ decreased under the combined stress of poor light and low temperature, but they can be increased with the treatment of Co Cl2. The treatment of Co Cl2 could also relieve the decreased photochemical efficiency of pepper seedlings under the combined stress of poor light and low temperature and and enhance the ability of plants’ photosynthesis.4. The level of MDA which is the final product of membrane lipid peroxidation increased with the stress time prolonging included low temperature and poor light. The activity of SOD and CAT in active oxygen scavenging enzyme system showed a trend from rise to decline. The activity of POD was increased which is harmful for plants. With the treatment of Co Cl2 the content of MDA decreased significantly. The activities of SOD and CAT increased significantly, but the activity of POD decreased. The treatment of Co Cl2 could also contribute to the promotion of the active oxygen scavenging system function and could protect stability and integrity of the cell membrane.5. The content of free proline increased and soluble protein decreased with the stress time prolonging of low temperature and poor light. While the treatment of Co Cl2 increased the content of free proline significantly which induced by the combination of poor light and low temperature, the content of soluble protein and the capacity of regulating cell infiltration could be increased, it also contributed to improving cell membrane permeability.All results show that: A certain concentration of Co can improve the growth and development of pepper under the combined stress of poor light and low temperature, and can achieve ideal results in photosynthetic gas exchange parameters, chlorophyll fluorescence, antioxidant enzyme systems, cell membrane permeability and other physiological and biochemical indexes. In a word, pepper can be more resistent to the combined stress of poor light and low temperature with the treatment of Co Cl2.