Experimental Study On The Impacts Of Increasing O₃ And CO₂ Concentrations On Crops

With the rapid development of industrialization and urbanization, an increase of the tropspheric O₃ and CO₂ concentration at striking rates caused more effects on biosphere, especially on crops. Many research on this were made before, which ranged largely in the effects of single factor and some of which studied the interactive effects of O₃ with SO₂, NO₂, water stress, acid rain as well as ultraviolet-B. But few study was about the interactive effects of O₃ with CO₂ on crops. In China, effects of elevated O3 and/or CO₂ on crops are of great concern to growers, scientists and governments. But in the past research on interaction of double levels of O₃ and CO₂ on crops was not taken. This paper was the first time to study systematically the impacts of double levels of O₃ and CO₂ alone or in combination on soybean by using OTCs. The study demonstrated that O₃ and CO₂ could make great impacts on the biomass and yield of soybean. This paper may be helpful for the assessment of crop loss from increasing of O₃ concentration and interaction of O₃ and CO₂ on crops. It is also useful in the identification of an critical level to protect crops against adverse effects by O₃ in China.The main conclusion were listed below:1. The double level of O₃ alone exposure resulted in typical visible foliar symptoms; shorter soybean height; decreased root nodule, biomass, yield; higher contents of proteins and less fat in seed; increasing of vitamin C, soluble protein concentration and less soluble sugar in leaves. The effects accelerated process of lipid peroxidation, had a detrimental effect on the membrane protective system, accelerated the process of leaf senescence.2. The double level of CO₂ singly exposure had obverse effects on plant height, root nodule, biomass as well as yield and adverse effects on seed quality. The exposure also caused less Superxide anion radical, MDA, vitamin C, soluble protein, Calmodulin, Abscisic Acid and more SOD, soluble sugar in leaves.3. The mixed double levels of O₃ and CO₂ may alleviate the negative effect of O₃ on biomass and yield of soybean. The mixed treatments lead to promoting lipid peroxidation and more fat as well as dropping protein in seed. The interaction in visible foliar symptoms, lipid peroxidation, content of vitamin C and Abscisic Acid expressed that the adverse effects of O₃ was greater than the obverse effects of CO₂. The obverse effects of CO₂ was greater than the adverse effects of O₃ in plant height, root nodule, biomass and yield.4. The sequential double levels of O₃ and CO₂ lead to latter and lighter visible foliar symptoms than the concurrent double levels of O₃ and CO₂. It had more obvious alleviation of CO₂ to the negative effect of O₃ on plant height, root nodule, biomass and yield than the concurrent treatment.