PHYSIOLOGICAL POTENTIAL OF TEPHROSIA NOCTIFLORA BOJER EX BAKER SEEDS UNDER ABIOTIC STRESS FACTORS.

Tephrosia noctiflora is an infesting weed species recorded in agricultural crops and pastures in Alagoas, Northeast Brazil, associated with economic losses in local cattle ranching due to literature reports of management difficulties and potential toxicity from putative rotenoids. This study evaluated the ecophysiology and seed resilience under abiotic stresses to estimate its persistence in pasture areas. Five temperature regimes were evaluated (20, 25, 30, 35, and alternating 20 to 30 °C) under light and dark conditions. At 30 °C, intact and acid-scarified seeds were subjected to thermal stress (80 to 240 °C for 5 minutes), aluminum toxicity (0.0 to 6.0 mmolc.dm-3), and osmotic stress (-0.3 to -1.5 MPa). Germination peaked at 20 °C, 30 °C, and under the alternating regime in the presence of light, indicating preferential positive photoblastism, while declining markedly at 35 °C. Thermal stress from 120 °C resulted in complete embryo mortality, whereas exposure to 80 °C promoted physical dormancy release. Aluminum reduced germination starting at 1.5 mmolc.dm-3, with low germination rates observed at higher concentrations; however, seeds retained viability, demonstrating tolerance to the acidic and aluminum-rich soils typical of Alagoas and the Northeast region. Osmotic stress progressively restricted germination, reaching complete inhibition at -1.5 MPa and inducing root plasticity under moderate water deficit conditions. Seeds of T. noctiflora exhibit high physiological resilience against chemical and hydric limitations, contributing to its colonization success and the persistence of toxicological risks to grazing livestock.