Effects of environmental variables and foliar traits on the transpiration rate of cocoa (Theobroma cacao L.) under different cultivation systems

Abstract

The response of plant species to environmental conditions influences changes in functional traits associated with the process that determines biological fitness and ecosystem processes. However, documenting these responses remain largely elusive in cultivation systems. We analyzed how environmental variables and leaf traits have effects on the transpiration rate of cocoa (Theobroma cacao L.) trees compared among different cultivation systems. Fieldwork was carried out at the Sara Ana experimental station in Alto Beni, La Paz, Bolivia. We sampled four trees in each of eight plots; four plots for each cultivation system (organic monoculture vs. organic agroforestry). From each tree, two mature, sunlit and healthy leaves were collected to make measurements of foliar traits and environmental variables. We found that canopy cover was higher in the agroforestry system. The specific leaf area was greater in agroforestry but the stomata size was significantly higher in the monoculture system. Temperature had a positive relationship with transpiration, whereas canopy cover and specific leaf area had a negative relationship in the agroforestry system. Cultivation system caused changes in microenvironmental conditions and on the expression of leaf traits that regulate water flow through the plant. Thus, the mutual effects of canopy cover, larger leaves and smaller stomatal size may drive a more efficient water use by reducing the transpiration rate of plants growing in agroforestry systems.