Growth and physiological response of mango (<i>Mangifera indica</i> L.) cv. Alphonso under elevated CO2 conditions

Abstract

Atmospheric CO2 concentration is expected to reach 460-560 ppm by the year 2050 with an increase of 3.2-4.0°C in temperature. Elevated CO2 and temperature affect fruit crops to a greater extent by affecting flowering, yield and quality of fruits. In the current study, the effect of eCO2 on mango cv. Alphonso was examined under open top chambers (OTC), with ambient CO2 (380 ppm) and elevated CO2 (550 ppm) levels, which were compared with the plants grown outside OTC under ambient conditions. The results revealed that the maximum number of vegetative shoot emergences was observed in OTC under both eCO2 and aCO2 conditions. The photosynthetic rate declined by 25% inside OTC due to increased air and leaf temperature compared to ambient plants placed outside the chambers. Significantly higher reproductive shoots emerged under aCO2 conditions, whereas, no reproductive shoots were observed in aCO2 under OTC, however, few reproductive shoots were observed under eCO2 in OTC. The stomatal number was increased inside OTC chambers under aCO2, but the same was not observed under eCO2 conditions. The other physiological parameters, such as specific leaf weight, chlorophyll content, relative water content, stem girth and total wax content were appeared to be better in eCO2 conditions compared to aCO2 inside OTC and ambient conditions outside OTC. The increase in stomatal number and complete repression of flowering inside OTC at aCO2 was mainly due to higher temperatures compared to outside and this effect of temperature was reduced by eCO2. The results of the study indicated that eCO2 may improve growth rates, flowering and reduce water loss in mango plants.