Effects of Salinity Stress on Seed Germination Characteristics of Two Medicinal Species Thymus kotschyanus and T. daenensis

Abstract

The genus Thymus is perennial medicinal plants belong to the Lamiaceae family<br />that is used for different propose in pharmaceutical industry. Environmental stresses,<br />particularly salinity, are considered as the major factor reducing plant growth. The purpose of<br />this study was to investigate the effects of salt stress on germination characteristics and<br />seedling morphology in two medicinal species of T. kotschyanus and T. daenensis. A factorial<br />experiment was conducted using completely randomized design with four replications and<br />seven salinity levels. The salinity factor were included of 0, 50, 100 150, 200, 250 and 300<br />mm NaCl. Data were collected for germination percentage, germination rate, time means of<br />germination, radicle length, plumule length, seed vigor, and allometry ratios. The overall<br />means of germination percentage, germination rate, radicle length, and seed vigor were lower<br />for T. daenensis as 41.44, 0.28, 1.15 and 1.87 than those for T. kotschyanus as 54.32, 0.37,<br />1.81 and 2.8, respectively, indicating more tolerant to salinity for T. kotschyanus than that for<br />T. daenensis. Results showed that by increasing salinity, the germination percentage, rate of<br />germination, plumule length, radicle length, and seed vigor were reduced in both species. The<br />slop of reduction was higher for T. daenensis than T. kotschyanus. In other words, T.<br />kotschyanus was more tolerate to salinity than T. daenensis. It was concluded that this genus<br />could be cultivated in environments, which plants are not in expose to salinity.