Florescimento in vitro de orquídeas: fundamentos e respostas a fatores ambientais e hormonais

Abstract

In vitro flowering of ornamental orchids constitutes a promising strategy to reduce the long developmental cycle of these species and minimize their dependence on environmental stimuli, contributing to the production of more uniform plants with greater commercial value. This thesis aimed to integrate theoretical and experimental approaches related to the factors regulating floral induction, with emphasis on the genus Dendrobium. Through a critical and bibliometric analysis of the literature, it was verified that flowering under in vitro conditions is a multifactorial process resulting from the interaction between physiological and environmental factors, such as hormonal balance, metabolic status, and cultivation conditions, especially light and temperature. The review also highlighted different morphogenic manifestations associated with flowering, including direct induction from protocorm-like bodies and after plantlet regeneration, emphasizing the potential of this technique to accelerate breeding programs, species conservation, and studies related to reproductive mechanisms. Despite the advances observed, protocol standardization remains limited, highlighting the need for integrated approaches to improve the efficiency and reproducibility of cultivation systems. In the experimental stage, the effects of growth regulators and thermal conditions on flowering, as well as on the physiological and biochemical responses of Dendrobium aggregatum cultivated in vitro, were evaluated. The results demonstrated that lower temperatures associated with the application of growth regulators, especially 2.0 mg L⁻¹ BAP combined with 0.1 mg L⁻¹ NAA, promoted higher flowering rates, reaching up to 85% of flowering plants. Additionally, changes in hydrogen peroxide levels and antioxidant enzyme activity indicated the involvement of oxidative metabolism in floral regulation. Overall, the results demonstrate that in vitro flowering in Dendrobium depends on the interaction between temperature and growth regulators and is associated with physiological responses related to cellular redox balance. These findings contribute to the improvement of production protocols and to the advancement of knowledge regarding the reproductive biology of ornamental orchids.