Dynamics of gas exchange and chlorophyll fluorescence parameters of cocoa genotypes in response to water deficit

Abstract

The effect of drought stress on the photosynthetic gas exchange parameters of twenty cocoa genotypes (Theobroma cacao L.) was examined under glasshouse conditions. Photosynthesis, chlorophyll fluorescence and stomatal conductance evaluated in 100% and 50% of the field capacity revealed significant differences between non-stressed and stressed plants and different genotypes. Among the genotypes, the percentage reduction in terms of photosynthetic rate (29.22 and 27.68% respectively), chlorophyll fluorescence (4.2 and 4.01% respectively) was low in VTLCH 3 and VTLCH 4 while the highest reduction in stomatal conductance (48.70 and 50%) and transpiration rate (57.81 and 56.80%) under stress regimes was also recorded in the same genotypes. Therefore, VTLCH 3 and VTLCH 4 were grouped as water stress tolerant genotypes based on the dynamics of gas exchange parameters. Thus, these two genotypes could be utilized for cultivation in Tamil Nadu condition and in further breeding programs.