Desempeño fisiológico de tres genotipos de theobroma cacao l (malvaceae)bajo diferentes regímenes hídricos en la etapa de vivero

The aim of this study was to evaluate the physiological response of cacao genotypes under different water regimes during the nursery stage. We evaluated relative growth rate, specific leaf area, water use efficiency, relative water content and stable carbon isotopes in three genotypes of Theobroma cacao (IMC67, PA46 and PA121). Water regimes of 100%, 50% and 25% of the substrate field capacity were applied during 98 days after emergence. The growth variables measured were: dry weight of shoot, total dry weight, stem diameter, leaf area and leaf dry weight. To evaluate water use efficiency was measured rate of photosynthesis and transpiration. Relative water content was calculated using fresh weight, turgid weight and dry weight of leaf discs. Also, it was measured the isotopic discrimination carbon. We found that 50% water restriction was not enough to cause stress and did not differ from 100%. There was no difference in growth between genotypes. IMC67 genotype had a better efficient use of water according to carbon isotope discrimination, whereas PA121 and PA46 genotypes did not show the same behavior. As show by specific leaf area, the greater capacity of leaf growth occurred in the genotype PA46, contrary to what was found for IMC67. Given the age, 53 and 68 were the periods of high growth, which did not occur for days 38, 83 and 98.