The effect of irradiance level on cocoa (Theobroma cacao L.): I. Growth and leaf adaptations

I.K.A. Galyuon, C.R. McDavid, F.B. Lopez, J.A. Spence


Improved tolerance of cocoa to full sunlight has the potential of increasing yields while reducing the need for shade management. The effects of irradiance on growth and leaf adaptations in plants grown from seeds or cuttings and subjected to full sunlight (1800 ?mol m-2 s-1) or shaded conditions (900 ?mol m-2 s-1) were investigated. Leaf size, internode length, total leaf area, and dry matter per plant were significantly reduced while leaf thickness, specific lead weight, stomatal density, and leaf number per plant were increased in full sunlight. The lead area ratio, net assimilation rate, and relative growth rate were also reduced under full sunlight, although some genotypes, especially TSH 919, TSH 1188, and their progenies, seemed to grow better in full sunlight than in shade. The results suggest that some leaf adaptations may influence tolerance to high irradiance


Cocoa; Trinidad-selected hybrids (TSH); Growth; Leaf adaptations; Irradiance

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