Agroforestry Shading Mitigates Light Stress in Cocoa (Theobroma cacao L.) by Improving Photosystem II Efficiency Assessed via Chlorophyll Fluorescence (Fv/Fm)

Background: Cocoa is a shade-tolerant species. Excessive light can induce photo-oxidative stress and photosystem II (PSII) photoinhibition in cocoa. In agroforestry, the tree canopy plays a key role in modulating the light microclimate and could therefore contribute to cocoa photoprotection. Aims: This study evaluates the effect of different agroforestry shading levels on PSII efficiency, estimated from the maximum photochemical yield (Fv/Fm) measured after dark adaptation. Study Design: Field experiment comparing three light environments on mature cocoa trees (O0: full sun; O1: moderate shade; O2: dense shade). Place of Study: Experimental cocoa agroforestry sites in Côte d’Ivoire (Azaguie, Soubré, and Blé/Divo). Methodology: Three light environments were implemented on mature cocoa trees: full direct light (O0), partial shade (approximately 30%, O1), and dense shade (30–60%, O2). The effect of shade on Fv/Fm was assessed using a Kruskal–Wallis test complemented by post hoc analyses (α = 5%). Results: Shade had a significant effect on PSII efficiency (p-value = 0.009). Cocoa trees under full sunlight showed a reduced Fv/Fm ratio (0.752 ± 0.015), indicating strong photoinhibition, whereas trees under moderate shade (0.796 ± 0.003) and dense shade (0.785 ± 0.005) exhibited markedly higher values. O1 and O2 did not differ significantly, suggesting that a moderate shade level is sufficient to provide effective protection against light stress. Conclusion: These results indicate that agroforestry shade reduces light stress in cocoa while increasing PSII performance. They highlight the value of moderate shade as a management approach to prevent photoinhibition. It is recommended that future studies should assess long-term yield and physiological resilience under optimised shade regimes.