چكيده انگليسي :
The increasing trend of salinization represents a great threat to the growth of crop plants, particularly medicinal plants. Comparative responses of the medicinal species to the salt stress is little known. In this research we conducted three experiments. In the first experiment, morphological, physiological and biochemical responses in relation to grain and essential oil yield penalties of three genotypes of anise (Pimpinella anisum L.) (Isfahan, Marvdasht, and Borazjan), fennel (Foeniculum vulgare Mill.) (Shiraz, Yazd, and Kashan), and ajwain (Trachyspermum ammi L.) (Karaj, Nahadjan, and Ghahdrijan) were examined under normal (control) and brackish (100 mM NaCl) irrigation water conditions in a factorial arrangement based on a randomized complete block design with three replicates in a 2-year field experiment. The second experiment was performed in green house, based on a factorial randomized complete block design, where pot-grown plants of two genotypes from each of the three medicinal species of fennel (Shiraz and Yazd), ajwain (Nahadjan and Ghahdrijan), and anise (Isfahan and Marvdasht) were exposed to water salinities of 0 (control), 40, 80, and 120 mM NaCl and comparative changes in the leaf photosynthetic pigments, osmoticums, antioxidative enzymes, ionic homeostasis, essential oil concentration, and plant growth were assessed. The third experiment was arranged in factorial based on a randomized complete block design with three replications in Petri Dishes using two genotypes from each of the three medicinal species of fennel (Shiraz and Yazd), ajwain (Nahadjan and Ghahdrijan), and anise (Isfahan and Marvdasht), where the germinating seeds and seedlings were exposed to water salinities of 0 (control), 25, 50, 75, 100, and 125 mM NaCl and comparative changes in the seedling antioxidative enzymes, free proline concentration, phenolic concentration and plant growth were assessed. The results of the first study showed that chlorophyll-a and K+ concentrations, shoot dry mass, grains/plant, 1000-grains weight, grain yield components and essential oil yield were decreased but H2O2 and Na+ concentrations, electrolyte leakage, lipid peroxidation, and Na+/K+ were increased upon exposure to the brackish water. In the second experiment, genotype- and species-specificities were observed in the salt-induced modifications of these physiological attributes. Decreasing in growth, total plant dry mass, root volume, relative water content (RWC), and K+ concentration concomitant to increasing in the catalase, ascorbate peroxidase, and peroxidase activities, malondialdeheyde, total soluble carbohydrates, proline and Na+ concentrations, Na+/K+, and essential oil concentration were common to the examined species and genotypes within each species. The K+ concentration of the stressed plants of anise genotypes was smaller, giving shape to a greater Na+/K+ than those of the fennel and ajwain. Unlike anise, fennel and ajwain genotypes retained and/or increased the chlorophyll and carotenoids concentrations when exposed to 120 mM NaCl. Anise and ajwain genotypes indicated smaller grain essential oil concentration and yield and shoot dry mass, particularly upon exposure to the brackish water. Germination percent and velocity and root and shoot lengths were suppressed upon exposure to saline water. Despite the increasing trend of the proline and polyphenol concentrations and catalase and peroxidases activities, ascorbate peroxidase activity of germinating seeds decreased with an increase in NaCl concentration. The data obtained were suggestive of distinct salt-induced physiological and biochemical responses that are important to differential yield penalties of these species and potentiate fennel to being irrigated with brackish water. This potency of fennel was brought about, in part, through an ability to exclude Na+ and hence refrain from ion toxicity and partially through osmoregulation and, therefore, sustaining water status and RWC.
