Effect of Seed Treatments on Seed Germination and Seedling Growth of Madhuca longifolia var. longifolia (“Mee”)

Madhuca longifolia (Koenig) J.F. Macb. var. longifolia is a forest tree species with high reforestation potential in the dry zone of Sri Lanka. Seasonality in seed production and lack of plant production are the drawbacks of this species regenerating naturally. Seeds were treated with gibberellic acid (GA3), potassium nitrate (KNO3), distilled water (DW), and scarified in addition to control without any treatment. Data were evaluated for germination and seedling growth under ex vitro and in vitro conditions. The objective of this study is to determine the dormancy associated with M. longifolia seeds and the effect of pre-treatments on seedling growth. Mechanically scarified seeds, under ex vitro conditions, showed higher germination than all the other treatments after 28 days and a significantly higher percentage (p<0.05) than the control under both light (90.00%) and dark (85.45%). Dark conditions stimulated germination significantly within the first seven days of sowing. The highest shoot growth was observed for GA3, KNO3, and DW (8.3, 8.6, and 8.5 cm, respectively) treatments while rooting was not significantly affected by the applied treatments. In vitro germination was tested for de-coated, surface sterilized seeds on half-strength liquid Murashige and Skoog (½ MS) media with different concentrations of benzylaminopurine (BAP) such as 0, 0.2, 0.5, and 1.0 mg/L. The germination percentage of ½ MS with 0.5 mg/L BAP (77.71%) was higher than all the other media compositions. Results revealed that M. longifolia seeds show a lower level of germination due to physical dormancy, and it can be released by mechanical scarification.