Effect of elevated CO 2 , high temperature, and water deficit on growth, photosynthesis, and whole plant water use efficiency of cocoa (Theobroma cacao L.)

• Published in: International journal of biometeorology 2020-01, Vol.64 (1), p.47
• Main Authors: Hebbar, K B, Apshara, Elain, Chandran, K P, Prasad, P V Vara
• Format: Article
• Language: English
• Subjects: Cacao; Carbon Dioxide; Photosynthesis; Plant Leaves; Temperature; Water
• ISSN: 1432-1254

In this study, the response of 6-month-old cocoa (Theobroma cacao L.) seedlings to elevated CO concentration [ECO ], elevated temperature [ET], and their interaction with water deficit stress was studied in an open top chamber (OTC). Each OTC was maintained at chamber control (400 ppm CO ), [ECO ] 550 ppm, [ECO ] 700 ppm, ET 3 °C above chamber control, and ET 3 °C + [ECO ] 550 ppm. Inside each OTC, a set of plants received moisture at 100% FC, while the other set was at 50% FC, which was the water deficit stress treatment. Increasing the CO concentration in cocoa increased photosynthesis (Pn) by 27%, which resulted in high biomass accumulation, thus improving the whole plant water use efficiency (WUE). The impact of high temperature (T ), around 39 °C in ET treatment against 36 °C in chamber control, is quite severe on Pn, leaf Ψ, and biomass accumulation. Similarly, water deficit at 50% FC resulted in the leaf Ψ reducing to - 14.06 bars at which Pn, leaf area, and biomass were significantly reduced. [ECO ] could ameliorate the negative effect of high temperature and water deficit stress to certain extent. However, the relative response of cocoa seedlings to [ECO ] in improving Pn, leaf Ψ, biomass, and WUE was greater under 50% FC compared to plants at 100% FC suggested additional advantage of [ECO ] to cocoa under water limited conditions.