2.2 Media, Culture Conditions and Stress Treatments
The sterilized S. hieraciifolia achenes and T. parvulaseeds aseptically germinated at MS medium (pH 5.8) (Murashige and Skoog, 1962) which is sterilized by autoclaving for 15 min at 121°C and 1 atm pressure. The nutrient basal medium is consisted of MS including vitamins (4.95 g L-1), 1% sugar (w/v) and 0.8% agar (w/v). This basal medium was supplemented with various growth regulators including naphthalene acetic acid (NAA, 0.1 mg L-1), kinetin (1 mg L-1), isopentenyl adenine (2IP, 2 mg L-1) at different developmental stage of the plants.S. hieraciifolia and T. parvula plants were grown until their shoots develop (for 45 days and 35 days, respectively), at 24±2 °C, on light intensity 400-430 μmol photons m-2s-1 and 16h light/8 h dark photoperiod. Subsequently, S. hieraciifolia and T. parvulaplants were exposed to salt stress through 0, 150, 300, 450 and 600 mM NaCl supplements to MS media for 7 d. Salt concentrations were gradually enhanced by 150 mM NaCl supplements with 2 d intervals until reaching the last salinity levels (150, 300, 450 or 600 mM). Thus, gradually increasing salt concentrations were applied to the plants with transferring of the plants from previous salt concentration to the next concentration. Five different NaCl treatment groups (0, 150, 300, 450 and 600 mM NaCl) were constituted for S. hieraciifolia andT. parvula . Morphological observations and, following measurements and analysis were conducted.