Physiological and growth responses of 12 fennel (Foeniculum valgare Mill) genotypes to water potential at seedling stage

Water deficit is a common and major constrain for agricultural production in arid and semi-arid parts of the world like Iran, to the extent that it might threaten the nation’s food security in years to come. Seed germination is a crucial growth stage that is often affected by environmental stresses, including drought. This study investigated the effects of four levels of water potential (i.e. 0, -0.2, -0.4 and -0.6 MPa) on germination, seedling characteristics, soluble carbohydrates, proline and polyphenols contents, and antioxidant enzymes activities of 12 fennel genotypes. Low water potentials reduced germination percentage and speed of germination, seedling fresh and dry masses, shoot length and superoxide dismutase specific activity, though it led to increases in root length, soluble carbohydrates, proline and polyphenols contents, and catalase specific activity. The 12 genotypes according to the degree of decreases in germination percentage at -0.6 MPa compared to control, were classified into three groups, including drought-tolerant (Shiraz, Yazd, Kerman and Mashhad), moderately-tolerant (Hamadan, Kashan, Bushehr and Urmia) and drought-sensitive (Birjand, Ardabil, AviSina and Isfahan). Mashhad, as a drought-tolerant genotype, indicated the greatest germination percentage, seedling fresh and dry masses, root length, soluble carbohydrates, proline and polyphenols contents, and catalase and superoxide dismutase specific activities among 12 genotypes studied. The results obtained in this study demonstrate some key aspects of the drought tolerance-related characteristics of fennel at germination stage that may help elucidate the whole plant performance of fennel at drought-stricken areas, when integrated with results from field studies.