Seed Germination, Viability, Imbibition and Storage Behaviour of Radermachera xylocarpa (Roxb.) K. Schum.: A Research-Based Study

Radermachera xylocarpa (Roxb.) K. Schum. (family Bignoniaceae) is a large, ecologically significant deciduous tree native to the dry and moist deciduous forests of India. Due to habitat degradation, overexploitation, and poor natural regeneration, the species is considered rare and vulnerable in several regions. Efficient seed-based propagation is essential for ex-situ conservation, nursery production, and forest restoration. This study synthesizes research findings on seed morphometrics, imbibition kinetics, viability testing via tetrazolium (TZ) staining, germination performance across different substrates and pre-treatments, and short-term desiccation and storage behaviour. Results show that R. xylocarpa produces large, thin, winged, membranous seeds with high seed coat permeability, leading to rapid triphasic water imbibition. Optimization of the 2,3,5-triphenyltetrazolium chloride (TZ) test revealed that a 0.5% concentration with a 24-hour staining period yields accurate viability detection (up to 91.00%), whereas higher concentrations or prolonged staining cause overstaining. Seed germination tests demonstrated that cocopeat substrate provides the highest germination capacity (62%) and superior seedling vigour compared to filter paper (23%), sand, or MS basal medium. Pre-soaking in exogenous gibberellic acid (GA3) was ineffective in improving germination over distilled water controls. Seeds exhibited orthodox storage behaviour, tolerating desiccation down to approximately 5.59% moisture content and maintaining high viability (68.15 ± 2.73%) after three months of low-temperature storage. These findings provide clear physiological guidelines for nursery propagation, seed testing, and long-term conservation of R. xylocarpa.