Evaluation of seed dormancy-breaking techniques for enhancing germination potential, seedling growth, and vigour of Carissa carandas L.

Carissa carandas L. is a versatile evergreen shrub of the Apocynaceae family and its fruit is rich in vitamins and antioxidants. It is commonly propagated by seeds, which are characterized by low germination rates due to the presence of a hard seed coat that causes physical dormancy and limits water absorption and gas exchange. In this study, the effects of different dormancy-breaking treatments viz., chemical treatment with potassium nitrate and thiourea at two concentrations (1% and 2%), hormonal therapy with gibberellic acid (GA3) at two concentrations (500 and 1000 ppm) and physical treatments (hot water and simple water immersion) were investigated on germination and seedling growth using a Randomized Block Design (RBD) with three replications and the statistical significance of each treatment was tested at the five percent probability level (p ? 0.05). Key germination indices, seedling growth parameters, and seedling vigour were observed. Among all treatments, 2% KNO3 was most effective in breaking seed dormancy that achieved significantly higher (86.33%) germination with accelerated completion of germination in 18 days and the highest (4.80) mean daily germination (MDG). Thiourea 2% attained a germination percentage of 82.91% and MDG of 4.36 while GA3 treated seeds had a lower germination percentage and MDG than KNO3 and thiourea treatments. The significantly highest seedling length vigour index (LVI) of 1085.1 and weight vigour index (WVI) of 12.67 were also obtained in 2% KNO3 treated seeds which was followed by 2% thiourea with LVI of 1003.6 and WVI 10.12 . Both LVI and WVI were significantly lower in GA3 treatments compared to KNO3 and thiourea treatments. The significantly lowest germination percentage (61.19%), MDG (2.78), LVI (575.8), and WVI (3.67) were recorded in the control. This study offers valuable insights into the efficient techniques for seed dormancy breaking and optimizing seed propagation techniques for C. carandas L.