Resposta de dipteryx odorata (Aubl.) Forsyth F. à aplicação de 24-Epibrassinolídeo: evidências de estímulo e inibição do crescimento

Abstract

We evaluated the effect of 24-epibrassinolide on the growth and development of young seedlings of Dipteryx odorata, the Tonka Bean tree, an Amazonian species of ecological and economic importance. The experiment was conducted in the nurseries of the Federal University of Pará (Altamira, Brazil), under 50% shade, on 115 seedlings divided into five treatments (0, 10, 20, 30, and 40 nM of the hormone). We measured morphological parameters (height, basal diameter, and number of leaves) and leaf physicochemical parameters (chlorophyll, nitrogen, moisture, and leaf temperature). To explore the associations of differences in everyone per treatment and choose the variables for modelling, we performed a principal component analysis. The effects of the treatments on these variables were evaluated using linear mixed-effects models with maximum likelihood estimation. Hormone dosages significantly influenced plant growth, with a marked positive effect at the 30 nM dose, resulting in greater gains in height, diameter, and number of leaves, as well as increased chlorophyll production. The 40 nM dose provided the best height/diameter ratio, indicating better plant stability and quality. The 10 nM dose, although positive for size, diameter, and growth rate, yielded less relevant results than higher doses. The 20 nM dose caused inhibitory effects, characterized by reduced growth and decreased chlorophyll production, suggesting a sensitivity window associated with high ethylene production. These results confirmed the importance of 24-epibrassinolide as a growth regulator capable of improving the physiological and morphological performance of Dipteryx odorata under semi-controlled conditions