Brassinosteroides e substratos no desempenho de mudas pré-brotadas (mpb) de cana-de-açúcar (saccharum officinarum)

Abstract

The choice of substrate and the use of brassinosteroids (BRs) are important strategies to enhance the development of pre-sprouted sugarcane seedlings (MPBs). This study aimed to evaluate the effects of combining different substrates and the application of brassinosteroids on the morphophysiological performance of MPBs. The experiment was conducted at the UEMA Experimental Farm in São Luís – MA, using a randomized block design with four treatments resulting from the combination of two substrates (S1: poultry litter + agricultural soil; S2: commercial substrate Carolina Soil®), and bud pre-treatment with and without BRs (0.1 μM). Morphological characteristics were assessed, including sprouting speed index, plant height, collar diameter, number of leaves, root volume and length, shoot and root dry mass, total dry mass, pruning dry mass, and Dickson quality index. Physiological traits such as leaf greenness index and chlorophyll a fluorescence were also evaluated. Exogenous application of brassinosteroids significantly improved the leaf greenness index (by 8.6%), root length (12%), root dry mass (35.2%), shoot dry mass (32.8%), total dry mass (36.8%), and Dickson quality index (26.8%). Substrate S1 showed better initial performance in plant height and pruning dry mass. This improved initial development may be related to the poultry litter in S1, which is rich in nutrients—especially ammoniacal nitrogen—that is released before fertilization and favors early seedling growth. The interaction between BRs and substrate S2 was notable for root volume, shoot and total dry mass, indicating a positive interaction between the growth regulator and the commercial substrate. This combination enhanced seedling development, whereas their individual use was less efficient. The exogenous application of brassinosteroids enhances the physiological and morphological benefits promoted by phytohormones. Brassinosteroids improve both physiological and morphological performance of MPBs, and the commercial substrate shows a positive response to BR application, making this combination recommended for producing more vigorous and higher-quality seedlings.