Pre-sowing Seed Treatments in Acacia catechu Willd.: A Critical Review of Their Biological Basis, Comparative Efficacy and Practical Implications for Forest Nursery Management

Abstract

Acacia catechu Willd. is an ecologically and economically significant deciduous tree of South Asian origin, prized for its heartwood-derived catechin, medicinal properties, tanning compounds, timber, and contribution to agroforestry systems across South and Southeast Asia. Reproduction through seed is the principal method of propagation for large-scale nursery and reforestation programmes, yet germination capacity in this species is severely constrained by physical dormancy arising from an impermeable seed coat that prevents water uptake under ambient conditions. This review critically examines the spectrum of pre-sowing treatments investigated to overcome seed dormancy in A. catechu, including mechanical scarification, hot water immersion, dry heat application, sulphuric acid scarification, alternative chemical treatments, hormonal and growth-regulator applications, biological treatments, and combined methodologies. The literature for this review was identified through systematic searches of multiple electronic bibliographic databases encompassing both major interdisciplinary platforms and field-specific resources. Databases searched included Web of Science (Core Collection), Scopus, Google Scholar, PubMed, CAB Abstracts, AGRIS (the FAO international agricultural and food science database), TREESEARCH (the United States Forest Service research archive), BioOne, and the International Seed Testing Association (ISTA) Seed Science and Technology database. The biological mechanisms underpinning each approach are discussed in relation to the anatomy of the A. catechu seed coat, and the relative efficacy of each category is assessed against published germination data. The review situates A. catechu germination research within the wider context of leguminous seed biology, revealing methodological inconsistencies, knowledge gaps, and practical recommendations for nursery practitioners. The evidence indicates that concentrated sulphuric acid scarification and optimised hot water treatments produce the most consistently high germination percentages, while mechanical scarification represents an accessible and effective alternative for resource-limited nurseries. Hormonal treatments, particularly gibberellic acid, demonstrate a supplementary rather than primary role. Standardised comparative trials employing agreed germination metrics remain necessary before universal protocols can be prescribed.