Comparison of solute-specific effects on seed germination characteristics of SM seed (Silybum marianum ) at the same osmotic potential under salinity and drought stress conditions

Salinity and drought tension, are the most important environmental factors that reduce growth and production plants in Iran, germination reduction and seedling establishment are the most important problems of these soils; knowledge of resistance to drought and salinity and also adaptation ratio in hard situations, is a prerequisite for implementing strategies of dry and saline soils resuscitation that can be irrigated with saline water. This test was examined in order to separate the effects of drought and salinity and different levels of concentration on SM (Silybum Marianum) germination characteristics in above tension conditions in Hamadan Agriculture and Natural Resources Research Center. The test was implemented in a completely randomized design with 8 treatments and 4 design replications and or reviewing of drought treatment from Glycol polyethylene 6000 in 4 levels with osmotic potentials (0 and -3.5 and -7.2 and -10.8 bar). Also for surveying of salinity treatment effect, sodium chloride salt was used in 4 concentration levels with osmotic potentials (0 and -3.5 and -7.2 and -10.8 bar). SM seeds were put separately after disinfection within sterilized Petri-dishes and were added 10 cc of sodium chloride salt and polyethylene glycol separately with different concentrations to each of them. Within experiment days, the rate of seed germination and also shoot and root length was measured and recorded; at the end of the experiment, fresh and dry weight of roots and shoots were measured. Results showed that concentration increase in salt and dry environments, caused germination reduction and other factors were measured, so that high concentrations of drought and salinity treatments have reduced the germination rate among 40 to 50 percent, respectively. Therefore, it is concluded that SM (Silybum Marianum) seeds resistance in drought conditions tolerance is better than saline, which its reason is concerned to specific effects of salts in saline conditions that reduces enzyme activity and less cell membrane permeability. Higher treatment levels of salt concentration cause root and shoot length reduction respectively 11 and 2 percent in relation with drought treatment conditions and then salts specific effects is significance at .01 and caused increase of the stem and roots length under drought tension conditions in related of the salinity. Higher treatment levels of salt concentration also reduces root and shoot dry weight, respectively 7.34 and 31.3 percent relative to drought treatment conditions, so the solute-specific effects are significant at level of 1 percent and increase root and shoot dry weight under drought tension rather than salinity. In fact, the specific effects of salts decrease enzyme activity and record of cell division in stem and root that leads to a drop in the growth of SM seedlings under salinity tension compared with drought tension.