COMPARATIVE PHOTOSYNTHESIS, WATER RELATIONS, GROWTH AND SURVIVAL RATES IN JUVENILE CRIOLLO CACAO CULTIVARS (THEOBROMA CACAO) DURING DRY AND WET SEASONS

Abstract

SUMMARYThis study deals with the ecophysiological response of Criollo cacao cultivars to water deficit during initial establishment phase in an agroforestry system under shade of four timber species using a randomised block design. CO2 assimilation rate (A), transpiration (E) and stomatal conductance (gs), water potentials, pressure–volume curves and fluorescence measurements were studied during two dry and wet seasons. Survival rates, basal diameter and leaf concentrations of K, P and N were also determined. All cultivars exhibited 60% reduction in gs with drought, resulting in 73% decrease in A and E. Despite lower A, electron-transport rates were not significantly affected, suggesting the existence of electron sinks. Photochemical quenching is negatively affected by drought in some cultivars, whereas relative quantum yield of photosystem II and non-photochemical quenching remained the same during both the periods. Cultivars with the highest osmotic adjustment coincided with the highest survival rates, whereas growth and leaf nutrient concentrations were similar in all cultivars.