Role of water stress as a stimulus for in vitro multiplication and its effects on biochemical response in Vellozia species

Papel do estresse hídrico como estímulo para multiplicação in vitro e seus efeitos na resposta bioquímica em espécies de Vellozia

ABSTRACT

Water stress impairs plant growth, resulting in the death of the plant in extreme cases. In vitro studies on stress-tolerant species can serve as the basis for improvement through genetic modifications aimed at minimizing damage and providing a controlled environment for performing biochemical and physiological assessments of plants under stress. The Velloziaceae family includes desiccation-tolerant and fire-resistant species; thus, these species can be used for analyzing protective mechanisms and reproductive responses to stress. We hypothesized that species with adaptability to survival under extremely dry conditions would respond to in vitro water stress through resprouting. This study evaluated the extent of water stress induced by the addition of sucrose, mannitol, or polyethylene glycol, the role of water stress as a trigger for in vitro multiplication, and its effect on biochemical responses in Vellozia jolyi, Vellozia punctulata, Vellozia pyrantha, and Vellozia seubertiana. Independent experiments were conducted by supplementing the following concentrations of sucrose, mannitol, and polyethylene glycol to the MS culture medium: sucrose (30 g L⁻¹ [control], 75 g L⁻¹, and 120 g L⁻¹) and mannitol (0.0 g L⁻¹ and 15.96 g L⁻¹) for V. pyrantha; sucrose (15 g L⁻¹ [control], 45 g L⁻¹, and 60 g L⁻¹) and mannitol (0.0 g L⁻¹ and 7.9 g L⁻¹) for the other species; and polyethylene glycol (50 g L⁻¹, 100 g L⁻¹, and 150 g L⁻¹). When sucrose and mannitol were added, shoots had grown in all species, showing significant differences between treatments only for V. pyrantha. Polyethylene glycol did not induce shoot growth but, instead, diminished plant survival. The highest concentration of polyethylene glycol increased proline levels in V. pyrantha. All four species were resistant to water stress, owing to their ability to survive and reproduce under high concentrations of osmoregulators. Our study provides evidence that proline acts as an osmoprotectant of V. pyrantha.

Index terms: In vitro propagation; osmoregulator; proline; stress-tolerant species.