Mejora de la nutrición y la arquitectura radicular de plántulas y vitroplantas de Theobroma cacao L. mediante biomasa de Porphyridium cruentum 

Abstract

Sustainable inputs combining nutrient provision with potential biostimulatory activity may improve cacao plant establishment while reducing dependence on mineral fertilizers. This study evaluated biomass suspensions of the red microalgae Porphyridium cruentum as the sole externally applied nitrogen (N) input for seed-derived plants and as a complementary input for fertilized somatic embryo-derived plantlets of Theobroma cacao L. The biomass contained 31.79 % protein, 33.69 % carbohydrates, and 27.69 % ash, together with a diverse amino acid profile and polyunsaturated fatty acids. Three greenhouse experiments were conducted. Seed-derived plants of genotype IMC67 received inorganic N, no externally applied N, or one of two concentrations of non-dialyzed biomass suspension. Somatic embryo-derived plantlets of genotype CCN51, treated at 20 and 90 days of age, received mineral fertilization alone or combined with dialyzed or non-dialyzed biomass suspensions. Growth, biomass, root architecture, stomatal conductance, and  the maximum PSII quantum yield (Fv/Fm) were analyzed using ANOVA. In seed-derived plants, the higher biomass concentration increased height, whereas the lower concentration promoted leaf development and secondary-root formation. Whole-plant biomass and physiological variables were unaffected. No significant effects were detected in 20 day-old plantlets. In contrast, both preparations increased mature leaf number, fresh biomass, and quaternary root formation in 90 day-old plantlets, while the dialyzed preparation also increased height and dry biomass. These findings show that P. creuntum biomass suspension can modify cacao shoot development and root system architecture depending on plant developmental stage, biomass concentration, and preparation method. The responses are consistent with nutritional and potential biostimulatory contributions, although their underlying mechanisms require further validation.