Respostas in vitro a estresses abióticos em Gliricidia sepium

Abstract

Brazil is home to the greatest biological wealth on the planet, with a highly diverse flora. The Fabaceae family is the third largest botanical family in terms of species and boasts significant taxonomic diversity. Within this family, Gliricidia sepium is a perennial legume of great economic interest due to its versatility, including biological nitrogen fixation and adaptation to adverse environmental conditions. Studying genotypes under abiotic stresses, such as salinity and water deficit, is essential, given that these factors negatively impact plant development and can trigger physiological and biochemical responses. This study evaluated the responses of twe accessions from the Active Germplasm Bank (AGB) of Gliricidia sepium at Embrapa Tabuleiros Costeiros to saline and water stress under in vitro culture conditions. The experiments were conducted at Embrapa Tabuleiros Costeiros, using WPM (Wood Plant Medium) culture medium supplemented with different concentrations of NaCl (0, 100, 150, 200 and 250 mM) for saline stress. Morphometric parameters such as biomass (leaves, stem and roots), chlorophyll (a and b) and proline content were analyzed. Increasing salinity significantly reduced seedling growth, with a decrease in primary root and shoot length. Fresh and dry matter of both leaves and roots also decreased progressively, while stem matter increased compared to the control. High NaCl concentrations inhibited leaf development, preventing the quantification of chlorophyll and proline levels in these treatments. The Vitrine accession had higher chlorophyll a and b contents compared to the Dores accession at lower concentrations. Regarding proline, the Dores accession showed a significant increase in leaves at 100 mM, while Vitrine showed greater accumulation in the absence of salt. Proline was higher in stems than in leaves, increasing with salinity in both accessions. In the water stress assay, seeds were grown in a WPM medium with Polyethylene glycol - PEG 6000 (0, 70, 140, and 210 g/L). A linear reduction in germination and development of normal seedlings was observed as the PEG concentration in the medium increased. Anatomical changes were detected in leaf and root cells, indicating adaptations to water deficit. We conclude that in vitro salt and water stress significantly affected the development of Gliricidia sepium, with distinct responses among accessions. Proline proved to be an effective biochemical marker for assessing stress tolerance in this species. These results contribute to understanding how Gliricidia adapts to adverse conditions, aiding management and genetic improvement strategies.