Physiological parameters of sesame plant under the influence of salinity stress and increase of carbon dioxide concentration

Salinity has considerable adverse impacts on productivity of agricultural plants. Soil salinity, resulting from natural processes or from crop irrigation with saline water, occurs in many arid and semi-arid regions of the world like Iran. Sesame (Sesamum indicum L.) is one of the pedalitic families (Pedaliaceae) and one of the long-standing cultivated plants. Cultivation areas of sesame in Iran and the world is about 6500 and 42 thousand hectares, respectively. Since our country is located in the dry and semi-arid region of the world, soil salinity and irrigation water are the major problems in the country's agriculture. Another factor limiting the production of the product in warm and dry areas is the warming of the air which is a global phenomenon that results from prolonged greenhouse gas emissions, such as carbon dioxide gas, and the consequence of rising fossil fuels, the destruction of forests and some of the activities that lead to the development of human life. Considering the increasing greenhouse gas emissions and the importance of planting sesame in stressful conditions, this experiment was conducted to evaluate the tolerance of sesame plants under salinity conditions and increase of carbon dioxide. In order to evaluate the effect of different Co2 concentration and salinity on growth and yield of sesame, a trial was arranged as factorial experiment with four replicates based on complete randomized design at Agrotron growth chamber in agronomy and plant breeding Dept. of Vali-e-Asr University of Rafsanjan. The growth media was the soil with the amount of 2 Kg per pot. Treatments were included Co2 concentration at two levels as ambient (380ppm) and elevated (700 ppm) and salinity stress including 0, 4 and 8 ds/m. Results indicated that leaf proline content and soluble sugar content significantly affected by Co2 concentration which is decreased from 0.28 Mmol/gr FW to 0.08 Mmol/gr FW with elevated Co2 concentration from 380 to 700 ppm. The peroxidase, polyphenol oxidase and phenylalanine ammonialaze enzymes were also affected by the interaction of salinity and carbon dioxide. Sodium content significantly decreased in 700 ppm Co2 concentration compare with 380 ppm. In both of Co2 concentrations, K shoot content significantly increased with increased salinity level. The results showed that increasing of carbon dioxide under salinity stress caused a significant decrease in root Na content. The proline and soluble sugar content significantly decreased higher Co2 concentration. Although increased salinity stress showed increased activity of peroxidase and phenylalanine ammonilase, high salinity reduced the shoot potassium content of in the shoot. In general, the results of this study indicate that sesame plant reacts to different levels of carbon dioxide and that these parameters and relationships can be obtained to predict experiments at higher Carbon monoxide concentration.