Gas exchange efficiency in Cocoa – Spanish elm agroforestry system in the northwest Antioquia, Colombia

Abstract

The cultivation of cocoa (Theobroma cacao L.) under agroforestry systems, generates beneficial environmental conditions for cocoa crop physiology. An experiment was conducted to evaluate the effect of shade trees (Spanish elm trees - Cordia alliodora (Ruiz & Pavon) Oken) planted along with cocoa (clone CCN51) under an agroforestry system on cocoa’s gas exchange parameters regarding the reduction of the light intensity over the cocoa-leaf canopy. The experiment was developed in the Centro de Investigación el Nus - Agrosavia, located in the municipality of San Roque, Antioquia. The experimental design used was a randomized complete block design for the cocoa planting distances from the first row of Spanish elm trees interfacing with the cocoa plantation (4 m, 7 m, 10 m, 13 m). The statistical analysis was performed by estimating the area under the curve (AUC) of each variable, using the trapezoid equation of the statistical environment SAS® 9.4, an analysis of variances was performed to determine if there were statistical differences between treatments, and Tukey’s test at 5% probability was used to estimated statistical differences between means. There were significant differences in the treatments regarding the net photosynthetic rate (A), stomatal conductance (gs), and transpiration rate (E). The highest values of gas exchange parameters were found in the plants located 13 m from elm trees, while the lowest values were presented at 4 m. Plants at 7 m and 10 m always showed intermediate values for all gas exchange parameters. In the same sense, plants at 13 m had a higher radiation use efficiency (RUE) compared to plants at 4 m. The arboreal component modified the environmental conditions on cocoa trees regarding its distribution, generating a differential response to the physiological behavior of cocoa plants.

Ecophysiological plasticity of Theobroma cacao L. clones in response to the structure and microclimate of agroforestry systems in Mexico

“…Larger stomata in the CC increase transpiration rates to achieve the highest photosynthetic rates (Monteiro et al 2016). Since cocoa is shadeadapted, the highest photosynthesis rate is performed at low radiation levels; this is possible due to photosynthetic enzymes and large occlusive cells with large pores for gas exchange (Gómez-Yarce et al 2020). Therefore, plants that grow in CC conditions can have thinner leaves and large SS, taking advantage of the available PAR and thus increasing the water use efficiency (Rozendaal et al 2006, Daymond et al 2011, Saavedra et al 2020.…”

Cacao agroforestry systems beyond the stigmas: Biotic and abiotic stress incidence impact

“…In cacao, there are no studies regarding the LUE plasticity as a response to different microclimate conditions and interspecific interactions inside the different CAFS plots. However, some studies approached photosynthetic responses under contrasting CAFS designs ( Gómez-Yarce et al, 2020 ) and evaluated contrasting cacao varieties ( Agudelo-Castañeda et al, 2018 ). These studies also reinforce the great plasticity of cacao genotypes and the importance of interspecific interactions in CAFS designs.…”