Application of Photosynthesis Models to Determine Light Requirements in Three Cacao Clones

Numerous articles show that light, water, CO2, and chlorophyll participate in the wonderful process of photosynthesis, and however, it is necessary to determine the conditions with which the assimilation of CO2 are optimized in the cocoa crop, a subject with conceptual divergences due to the understory origin of the plant. Photosynthesis in cocoa clones (e.g., CCN51, FSV41, and LK40) to establish their light requirements were characterized. The influence of radiation levels on CO2 assimilation (A) were evaluated. Measurements were made on the fourth leaf of mature branches using a portable infrared analysis of gas exchange (Ciras-3 PP SYSTEM ®) equipment with a light unit (universal PLC3 -RGBW), and simultaneously the soil moisture was recorded every 5 min. The A/PAR curves were created, and photosynthesis models were evaluated. The fittest models for A/PAR curves to estimate the parameters Amax, light saturation point, light compensation point, dark respiration, and photosynthetic yield (Φ) were selected. It was found that photosynthesis increased consistently when PAR increased but each clone at different rates. The highest A and (Φ) in CCN51, and the lowest in LK40 were shown. The best-fit models for A were that of Kaipiainen (2009), Smith (1935), and Ye (2007). The appropriate light range was set with relation 0.5 A max up to A max. For CCN51, it was 500–1500. For FSV41, it was 250–750. Finally, for LK40, it was 546–1000 μmol photons m2 s−1.