Effects of PEG-induced drought and salt stress on germination characteristics, changes in proline, carbohydrates and antioxidant enzymes in three Varieties Of Plant Medicine

A factorial experiment was done in completely randomized design with 3 replications inorder to evaluate the tolerance to drought and salinity stress in three cultivars ofmedicinal plants and classify the components of germination in terms of sensitivity toboth stresses. Treatments include the cultivars at 3 levels (Foeniculum vulgare, HibiscusSabdariffa, Cynara scolymus) and drought treatment at 4 levels (including control, 5, 10and 15 dS/m) and salinity treatment at 4 levels (including control, 100, 200, and 300 mMof sodium chloride). Obtained results of data analysis indicated that the effect of droughtand salinity on tested characteristics of cultivars was significant at 1% level. Furthermore,a number of traits including germination rate and percentage, root length, stem length,total dry and wet weight, salt showed a decreasing trend through increasing the levels ofdrought and salinity; and the osmotic adjustment, proline and carbohydrate weregradually increased in ground and aerial organs as the result of enhanced drought;however, this increasing trend was also observed in salinity stress, so that the minimumvalue was related to the control level and the maximum level related to the highest levelof drought and salinity. Moreover, investigation of enzymatic changes in both ground andaerial organs indicates their increase in salinity and drought stress conditions. In general,the Hibiscus Sabdariffa cultivar led to more appropriate responses compared to thedrought stress (especially severe stress) in order to be protected from damages, but theHibiscus Sabdariffa cultivar was a relatively sustainable cultivar under salinity stresscondition and Foeniculum vulgare cultivar was the most sustainable cultivar undersalinity stress condition. Cynara scolymus cultivar was relatively sustainable underdrought stress condition and the most sensitive cultivar compared to other appliedcultivars under the salinity stress condition. Foeniculum vulgare cultivar was consideredas the most sustainable one under the salinity stress condition and the most sensitivecultivar under drought stress condition.