Growth and physiological responses of chinese cabbage and radish to long-term exposure to elevated carbon dioxide and temperature

Future forecasts for climate change predict the global mean surface air temperature rise by 1-4°C and double current atmospheric CO₂ level before the end of 21 century. Increased atmospheric temperature and CO₂ concentration are particularly important concerns for agricultural, horticultural and native plant production. In this study, effects of long-term exposure to elevated temperature and carbon dioxide (CO₂) on the growth and physiological responses of 3 cultivars of Chinese radish (Raphanus sativus L.) and 3 cultivars of Chinese cabbage (Brassica campestris L.) were examined. In result, the radishes exposed to elevated CO₂ for 90 days after sowing (DAS) resulted in little or no change in the root dry weights and the rate of photosynthesis compared with those grown in ambient levels of CO₂. In contrast, long-term exposure to elevated CO₂ in cabbage had variable effects on the leaf dry weight. As a result of acclimating to the elevated temperature, the radish 'Chunha' had a higher rate of photosynthesis, stomatal conductance and internal CO₂ concentration than in the control condition. Furthermore, the long-term exposure to a combination condition of elevated temperature and CO₂ increased root dry weights of the radishes 'Cheongdae' and 'Chunha' more than elevated temperature alone. The combination of elevated CO₂ and temperature stimulated the growth of roots more than that of shoots in the radish 'Chunha', and thus may have led a higher rate of nutrient uptake than other radish cultivars. In contrast, when the cabbage 'Chun-gwang' was exposed to a combination of elevated temperature and CO₂ for 90 DAS, the leaf dry weight decreased about 3-fold more than that only exposed to elevated CO₂ with drastic decreases in stomatal conductance, internal CO₂ and photosynthesis rate. When the cabbage 'Samjin' was exposed to either elevated temperature alone or both elevated temperature and CO₂ for 80 DAS, the decrease in the leaf dry weight was less than that of the other cabbage cultivars. Results indicated that the radish 'Chunha' and the cabbage 'Samjin' tolerated either elevated temperature alone or combination condition of elevated temperature and CO₂ more than other cultivars.