Differential effects of soluble salts on seed germination of Marrubium vulgare L.

Abstract

In Mediterranean basin and western Asia, Marrubium vulgare L. (Lamiaceae) presents a great demand in therapeutic and folk-medicinal usages. However, data about the seed ecology of this medicinally important shrub is scarce. Therefore, the knowledge of its germination requirements is needed for plant establishment in new potential areas. In present work, the effect of different salinities (NaCl, Na2SO4, CaCl2 and MgCl2) on the germination percentage (GP), germination velocity (GV) and salinity tolerance index (STI) of M. vulgare was studied. A complete randomized design was performed in which four salinity levels (0, 50, 100 and 150 mM) were used. The experiment was conducted in programmed incubator with light/darkness temperatures of 25 °C/15 °C at a 12–h photoperiod. The results revealed that seeds of M. vulgare were non–dormant and exhibited highest GP under non–saline conditions (∼ 95 %). Both GP and GV decreased significantly with increasing salinity irrespective of applied salt types. The inhibition of germination by soluble salts was in the following order: Na2SO4 > MgCl2 > CaCl2 > NaCl. The salinity tolerance index (STI) displayed that salinity tolerance of M. vulgare was highest for NaCl and lowest for Na2SO4 at the same concentration among the four saline solutions. These findings suggest that M. vulgare may be considered as a new moderate salt–tolerant species and a promising medicinal shrub for saline soil rehabilitation.