Study the impact of abiotic stress on photosynthetic potential of tropical tuber crops under elevated CO2

Abstract

Climate change and agriculture are interconnected processes, both of which take place on a universal scale. Global warming is expected to have significant impacts on agriculture. Most of the studies reported a positive impact in photosynthetic rate of C3 plants due to eCO2. However other players of climate change such as drought and rising temperature can harmfully affect crops. Cassava and sweet potato are two major tropical root crops grown in India. The main objective of the present study was to figure out the impact of adverse conditions of climate change such as water deficit stress and high temperature stress on photosynthetic potential of tropical tuber crops under elevated CO2 and there by identify crop/varieties suitable for changing climate conditions. The study was conducted during the period of October 2018 to July 2019 on four contrasting cassava and four contrasting sweet potato varieties. Observations on photosynthetic parameters viz., the net photosynthetic rate (Pn), stomatal conductance (gs) transpiration and sub-stomatal/intercellular CO2 concentration (Ci) were recorded using a LI6400 portable photosynthesis system, LI-COR Inc, Lincoln, USA. Elevated CO2 have positive effects on photosynthetic parameters under WDS free as well as WDS conditions in cassava as well as sweet potato. Even though WDS reduces photosynthetic rate, eCO2 could sustain greater Pn rate than ambient CO2 under WDS. Under eCO2 rising temperature can benefit cassava and sweet potato only under WDS free conditions. For cassava Pn was not significantly affected by temperatures. For sweet potato Pn significantly increased with rise in temperature. It indicates that increasing temperature is not a limiting factor for cassava and sweet potato, but beneficial for them under WDS free conditions. Responses of cassava and sweet potato to WDS and rising temperature are also influenced by the variety. Cassava variety Sree Athulya responses well to eCO2 as well as to rising temperature under WDS free conditions. Cassava variety Sree Vijaya can perform well under WDS compared to other varieties. Sweet potato variety Sree Arun exhibits higher Pn under WDS free conditions. Bhu Krishna and Kanhangad had high Pn under WDS as well as at higher temperature. From this study it can be concluded that tropical root and tuber crops especially cassava and sweet potato have a great potential for better adaptation at elevated CO2 environment under adverse climate conditions such as water deficit stress and increasing temperature. They can become crops providing food security for future environment under climate change.