Vegetative propagation of critically endangered mangrove Lumnitzera littorea (Jack) Voigt in Madu Ganga RAMSAR site of Sri Lanka, towards its conservation

Considering the environmental and specific socio-economic significance of the critically endangered mangrove L. littorea in Sri Lanka, this study was conducted to prepare a vegetative propagation protocol for this species with air layering and stem cuttings. Air layering was conducted with coir dust moistened with distilled water or 0.3% Indole-3-butyric acid (IBA) solution. Stem cuttings were treated with different concentrations of IBA, Naphthalene Acetic Acid (NAA) or Albert solution prior to be transplanted in the potting media. Approximately, 17.5% of the air layered branches produced roots, root initials or callus within 4-26 weeks whereas stem cuttings did not produce adventitious roots within the study period. It is essential to maintain an uninterrupted vascular connection between the area of rooting and the mother plant for adventitious root formation. Although a high phenol concentration was determined in stems, no structural barriers for adventitious root formation were identified in stems. In future research, it is recommended to apply a broader range of rooting hormones and combinations of hormones for stem cuttings to induce the formation of adventitious roots. Air layering was recommended to propagate this critically endangered species as it was the only successful method and is a cost-effective simple technology.