PHOTOSYNTHETIC LIGHT RESPONSE CURVES: ELUCIDATING THE PHOTOSYNTHETIC CAPACITY OF CACAO PLANTS (THEOBROMA CACAO L.) TO FULL SUN LIGHT IN CUNDINAMARCA, COLOMBIA

Background: Cacao is a neotropical crop of global economic importance, renowned for its ancestral use by pre-columbian cultures. Native to the Amazonian tropical rainforest, it is considered as a shady tree, although some hybrid genotypes can grow under full sun exposure. This ability to support different light levels vary from one clone to another and may be exploited to optimize crop yield. Questions: Are there differences in photosynthetic capacity under different levels of photon flux density (PFD) between ICS60, TSH565, FEAR5, CCN51 and EET8 cacao clones? Studied species: Theobroma cacao L. Study site and dates: Estacion Bambusa. Pacho, Cundinamarca, Colombia. October 2021. Methods: Physiological parameters were measured and analyzed under full light condition in two years-old cacao plants, to obtain photosynthetic response light curves. Functioning of the photosystem II (PSII) was evaluated through chlorophyll fluorescence parameters. Results: Significant differences were found in photosynthetic capacity at full sunlight exposition amongst clones, CCN51 showing the highest capacity for using high light, whereas TSH565 showed high photosynthetic capacity at lower PFD. On the other hand, the photochemistry activity was similar between clones, without evidence of PSII impairment, suggesting absence of photoinhibition under the conditions evaluated here. Conclusion: The responses found could guide and recommend the use and exploitation of these clones under specific in-field light conditions. The generated knowledge contributes to the implementation of adequate management practices that are aimed at optimizing the efficiency in the use of available PFD for enhancing photosynthetic rate, and, jointly, impact higher yields.