In plant breeding programs, one of the oldest methods is mutation breeding. Currently, mutation breeding has became popular among the breeders and scientists again with its use in plant biotechnology and due to some restrictions on the other techniques such as hybridization, cross breeding, and transgenic plants. Physical mutagens (X-rays, UV light, neutrons-alpha-beta particles, fast and thermal neutrons, especially gamma rays) are used more widely than chemical (ethyl methanesulfonate [EMS]) ones to artificially induce mutations (mutagenesis). However, among the physical mutagens, gamma-rays are widely used. During the irradiation of the seeds with ionizing radiation to generate mutants with desirable traits, reactive oxygen species (ROS) or free radicals can generate in cells. Although, these radicals/species generally can be very dangerous for the cell compartments, they can take an important role as a signal molecule activation of genes of antioxidant enzymes and proline, which are defense systems against these radicals in plant cells. In this chapter, usability of gamma-irradiation to provide the permanent gene expression of antioxidant enzymes and proline through the production of reactive oxygen species (ROS) is discussed.

It has been generally accepted that the morphology, physiology and biochemistry of plants are differentially affected by low-dose gamma ionizing radiation that is associated with the tolerance of plant species under biotic/abiotic stress. Therefore, the aim of this study is to investigate the protective role of low gamma irradiation pretreatment against salt and drought stress. For this aim, irradiated (100 Gy) and non-irradiated seeds of common vetch were cultured on an MS medium with separate addition of concentrations of NaCl (100 mM) and PEG-6000 (100g/l) under in vitro conditions. Morpho-physio-biochemical analyses were carried out on 14-day-old seedlings. The findings of this study clearly show that exposure to gamma irradiation pretreatment (100 Gy), alone or in combination with salt stress and drought stress, led to significant increases (p < 0.01) in dry matter accumulation, CAT, SOD and APX activities, proline contents and decreases in relative water content. However, alone, gamma irradiation pretreatment caused increased chlorophyll contents while decreasing MDA contents. Overall, these results suggested that low-dose gamma irradiation pretreatment can enhance the tolerance of common vetch seedlings against stress due to salt and drought.

Salt stress is one of the harmful abiotic stress factors. It makes agricultural lands especially in arid and semi-arid regions useless despite the efforts. More than six percent of total world agricultural lands are on the edge of vanishing due to salt stress. Salinity in soil occurs as a result of the factors such as lack of drainage, improper irrigation, excessive accumulation of soluble salts. Salinity limits the growth of plants. Despite the main results, some results of plants due to these limitations vary from species to species. The negative effects get morphological, biochemical and physiological reactions from plants. Slowed or stopped growth of roots and shoots, closuring of stomata, germination slowing, decreased or stopped development of seedling, deterioration of photosynthetic activity are the main reactions of plants to stress. On the other hand, plants also develop tolerance mechanisms as a result of some auxiliaries for surviving under adverse conditions. Plants have tendency to protect themselves from salinity with osmotic protectants synthesized by them such as sugars, proline, amino acids, glycine betaine. In this review, the responses of plants to salt stress were investigated and gathered.

This study was conducted to evaluate the alterations of some morphological and biochemical parameters of sunflower cultivars (‘08-TR-003’, ‘TR-3080’ and ‘TARSAN-1018’) under salt stress. For this aim, the seedling of sunflower cultivars was irrigated with tap water as a control, and with salinised water with 50, 150 and 250 mM NaCl for 30 days under controlled conditions. Salinity caused an apparent reduction in morphological parameters (plant height, leaf area, fresh weight, dry matter and water content) in all cultivars. Salt stress significantly (P<0.01) reduced the activity of glutathione reductase (GR) and ascorbate peroxidase (APX) activities in all sunflower cultivars expect for superoxide dismutase (SOD) activity. According to our results, SOD seems to play a key role in the antioxidative process in salt treated sunflower plants. Proline and malondialdehyde contents were significantly (P<0.05) increased under salt stress in all cultivars. Among the cultivars, ‘TR-3080’ had greater values in terms of morphological (plant height, leaf area, fresh weight, water content) and biochemical [GR, APX and SOD (secondly) activities and proline contents] parameters. In the light of these findings, cv. ‘TR-3080’ seems to be less affected by salt stress.