Breaking of dormancy in Rhubarb (Rheum ribes L.)

Freshly harvested seeds of Rhubarb exhibited a high degree of dormancy when germination has been studied in different temperatures in distilled water. In the present paper, different treatments including moist - chilling, immersing in NaOCl, acid scarification, surgical procedure, and treatment by CaCl2 and KNO3 were performed to determine the most effective method for removing dormancy in Rhubarb (Rheum ribes L.). When seed coats (pericarp + testa) were completely removed, the root and hypocotyls of excised embryo from dormant seeds did not elongate. This indicates that dormancy is imposed by the embryo and those inhibitors in seed embryo may be responsible for the dormancy. Germination was observed only in CaCl2 and KNO3 treatments. Optimum temperature for germination was 10 °C and dormancy was partially removed when seeds were germinated in different concentrations of CaCl2. Moreover, CaCl2 solutions promoted germination more than KNO3.