Morfofisiologia da bananeira cv. Williams cultivada in vitro em diferentes intensidades da radiação fotossinteticamente ativa e concentrações de sacarose

Abstract

The banana plant (Musa spp.) is a tropical fruit crop of great economic and social importance. However, the expansion of its cultivation is mainly limited by conventional propagation methods, making micropropagation a fundamental strategy for the largescale production of seedlings with high phytosanitary quality. In this context, adjusting the sucrose concentration and the intensity of photosynthetically active radiation (PAR) in in vitro cultivation contributes to optimizing photosynthetic efficiency and seedling growth. Thus, this work aimed to evaluate the impact of sucrose concentration and PAR on the photosynthetic machinery and in vitro growth of the ‘Williams’ banana plant, as well as the effects of these factors on the seedling acclimation phase. Thus, the experiment was conducted in a completely randomized design, in a 3x3 factorial scheme, corresponding to the combination of three sucrose concentrations (0, 15, and 30 g L⁻¹) with three PAR intensities (60, 120, and 180 μmol m⁻² s⁻¹). After 30 days of in vitro cultivation, growth, gas exchange, photochemical efficiency, pigments, and anatomical characteristics were evaluated. The results indicated that the total absence of sucrose, regardless of the PAR intensity, limited biomass production and seedling growth. However, treatments with the combination of 120 μmol m⁻² s⁻¹ of RFA and 15 g L⁻¹ of sucrose, and the treatment with the combination of 180 μmol m⁻² s⁻¹ and 30 g L⁻¹ of sucrose, provided improvements in the photosynthetic process and growth, with higher values of photosynthetic index and higher contents of photosynthetic pigments, and an increase in shoot length, leaf area, and shoot fresh mass. After the in vitro cultivation period, the seedlings were transferred to a greenhouse, where they remained for 30 days in the acclimatization phase. In this ex vitro phase, 100% seedling survival was observed, regardless of the treatments applied in the in vitro stage. However, the growth and vigor of seedlings under ex vitro conditions were influenced by the interaction between the intensity of PAR and the sucrose concentration used during in vitro cultivation, with better performance in treatments with 120 μmol m⁻² s⁻¹ associated with 15 g L⁻¹ of sucrose and 180 μmol m⁻² s⁻¹ associated with 30 g L⁻¹. Thus, it is concluded that the photomixotrophic cultivation of the banana var. ‘Williams’, under PAR of 120 and 180 μmol m⁻² s⁻¹ and with sucrose concentrations of 15 and 30 g L⁻¹, favors photosynthetic efficiency and growth, both in the in vitro phase and during acclimation, and constitutes an efficient strategy for micropropagation systems of this variety.