~ 833 ~ Journal of Pharmacognosy and Phytochemistry 2018; 7(2): 833-837 E-ISSN: 2278-4136 P-ISSN: 2349-8234 JPP 2018; 7(2): 833-837 Received: 05-01-2018 Accepted: 06-02-2018 Dheeraj Chatti Department of Plant Physiology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala, India Manju RV Department of Plant Physiology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala, India Correspondence Dheeraj Chatti Department of Plant Physiology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala, India Growth parameters contributing to increased drought tolerance responses in tomato ( Solanum lycopersicum L.) under elevated carbon dioxide Dheeraj Chatti and Manju RV Abstract Based on reports by the IPCC (Intergovernmental Panel on Climate Change), atmospheric CO2 concentration is rising. Plant growth is nearly always stimulated by elevation of CO2 and it has been found to ameliorate water stress in the majority of species studied. A pot culture experiment was conducted with three varieties of tomato i.e, Manulakshmi, Vellayani Vijay, Anagha with the objective to study the growth parameters contributing to increased drought tolerance responses in tomato (Solanum lycopersicum L.) under elevated Carbon dioxide using the Open Top Chambers (OTC) system. One month old potted tomato plants after shifting to OTC were subjected to water stress and then were allowed to recover. Various growth parameters like root weight, shoot weight, root shoot ratio, specific leaf area, total dry matter content were analysed both after stress and recovery. Elevated CO2 was found to increase growth parameters like root weight, shoot weight, specific leaf area and total dry matter production. Significantly higher values were recorded for root weight (0.92 g), shoot weight (6.88 g), total dry matter production (5.74 g) under elevated CO2 compared to open control. The challenges extended by the changing climate situations along with the global warming and reducing water availability, studies on drought tolerance responses as modified by elevated CO2 environments is highly significant. The results of this study will also help to design improved production technologies with suitable varieties for a changing climatic scenario. Keywords: climate change, global warming, elevated CO2, water stress, drought tolerance Introduction Agricultural productivity is decreasing worldwide due to detrimental effects of various biotic and abiotic stresses. Drought, which is the most important environmental stress, severely impairs plant growth and development, limits plant production and the performance of crop plants more than any other environmental factor. According to the Intergovernmental Panel on Climate Change (IPCC) [1] , by the year 2050, the current atmospheric CO 2 level of 384 μmol l - 1 (800 Gt) is predicted to rise to 1000 Gt. Increase in global average temperatures would further result in drastic shifts in the annual precipitation with a 20% reduction per year and about 20% loss in soil moisture and can increase potential evapotranspiration, leading to a more severe water deficit in arid and semiarid areas [2] . Carbon dioxide is the ‘food’ that sustains essentially all plants on the face of the earth as well as those in the sea. Carbon dioxide being a primary substrate for photosynthesis, a rising concentration will have a direct effect on plant growth by enhancing the production of assimilates although not proportional. Rising CO 2 generally stimulates C 3 photosynthesis more than C 4 . Doubling of the current ambient CO 2 concentration stimulated the growth of C 4 plants to the tune of 10–20% whereas that in C 3 plants was about 40–45% [3] . Elevated CO 2 increases photosynthesis, dry matter production and yield, substantially in C 3 species which is mainly attributed by the competitive inhibition of photorespiration [4] . Elevated CO 2 levels may enhance plant diversity and productivity in an entire ecosystem by decreasing stomatal conductance (g s ) and consequently increasing water use efficiency (WUE) and soil water availability [5, 6, 7] . Thus, plant growth and leaf area increase due to the improvement in water status by CO 2 enrichment under moderate drought conditions. Tomato (Solanum lycopersicum) is the widely cultivated vegetable in India and 2 nd most important vegetable crop next to potato. Current world production is about 100 million ton fresh fruits from 3.7 million ha. Considering the role of elevated CO 2 in the drought tolerance responses, the present investigation will help to understand the growth performance, productivity and water stress tolerance capacitiy of tomato and the results of this study will also help to design improved production technologies with suitable varieties for a changing climatic scenario.