Selection of salt tolerant lines at cell level using gamma ray with callus and suspension culture techniques in black carrots (Daucus carota L. ssp. sativus var. atrorubens Alef.).

The main objective was to select salt tolerant lines at the cell level of Hatay region's black carrot (Daucus carota L. ssp. sativus var. atrorubens Alef.) using callus and suspension culture techniques combined with gamma rays. Hypocotyl explants of http://www.scialert.net/asci/result.php?searchin = Keywords&cat = &ascicat = ALL&Submit = Search&keyword = in+vitro (in vitro)">in vitro grown plantlets was used for callus induction. Effective mutation dose was determined by gamma radiation treatment at various doses (0, 5, 10, 20, 30, 40, 50, 60 Gy) to black carrot calli after in vitro optimization steps. According to regression analysis, the number of plants regenerated from calli was found 8.36 Gy as effective dose. In the ongoing study, calli with 7 Gy, 8 Gy and 9 Gy gamma rays were multiplied by subculture for 5 times. Shoot induction was achieved in medium containing 1 mg L-1 BAP concentration. Average plant height, root length and branching number parameters of plants regenerated from calli were determined. Salt stress was applied to the plants acclimatized from in vitro to the climate chambers. changes in the amount of peroxidase (POD) and superoxide dismutase (SOD) activities of antioxidant enzymes and the changes in lipid peroxidation were revealed in leaf samples taken from plants that continued to live in a salty environment after the 14 days of the treatment. At the end of the study, salt tolerance increased in mutant plants have the plant number of 8-21, 9-19, 7-9, 9-2 and 9-8 compared to the control, and these were determined as possible mutant plants.

The defensive role of silicon in wheat against stress conditions induced by drought, salinity or cadmium.

In the crust of earth, silicon (Si) is one of the two major elements. For plant growth and development, importance of Si remains controversial due to the widely differences in ability of plants to take up this element. In this paper, pot experiments were done to study Si roles in improving salt, drought or cadmium (Cd) stress tolerance in wheat. Up to full emergence, all pots were watered at 100% field capacity (FC) every other day with nutrient solution without any treatments. Fifteen days after sowing, pots were divided into four plots, each with 40 pots for no stress (control) and three stress treatments; drought (50% FC), salinity (200 mM NaCl) and cadmium (2 mM Cd). For all plots, Si was applied at four levels (0, 2, 4 and 6 mM). Under no stress condition, Si applications increased Si content and improved growth as a result of reduced electrolyte leakage (EL), malondialdehyde (MDA) and Na+ contents. Under stress conditions, Si supplementation conferred higher growth, gas exchange, tissue water and membranes stabilities, and K+ content, and had limited MDA and Na+ contents and EL compared to those obtained without Si. Compared to those without Si, enzyme (e.g., superoxide dismutase, catalase and peroxidase) activity was improved by Si applications, which were linked with elevated antioxidants and osmoprotectants (e.g., free proline, soluble sugars, ascorbic acid and glutathione) contents, might providing antioxidant defense against abiotic stress in wheat. The level of 4 mM Si was most effective for mitigating the salt and drought stress conditions, while 6 mM Si level was most influentially for alleviating the Cd stress condition. These results suggest that Si is beneficial in remarkably affecting physiological phenomena and improving wheat growth under abiotic stress.

Physiological responses of the M1 sainfoin (Onobrychis viciifolia Scop) plants to gamma radiation.

Effects of gamma radiation on physiological responses of the M1 sainfoin plants were investigated. Seeds of sainfoin ecotype 'Koças' were exposed to 0, 400, 500 and 600Gy from a 60Co source at a dose rate of 0.483 kGyh-1. Irradiated and unirradiated seeds were sown into culture vessels containing MS-basal medium to be cultured for 30 days under in vitro conditions. At the end of this period, seedlings, which germinated from the radiated and unirradiated seeds, were transferred into pots in a growth chamber for 30 days more. Chlorophyll contents, activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as contents of monodehydroascorbate reductase (MDA) and proline were examined in unirradiated and irradiated 60-day-old seedlings. Overall, the activities of the antioxidant enzymes (SOD, CAT and GR) and contents of chlorophyll and proline in the leaves tended to increase after irradiation in a dose-dependent manner. By contrast, the activity of APX decreased. The lipid peroxidation characterized by the MDA content remained unchanged, except after irradiation to 500Gy. The highest CAT activity and the highest proline content were observed after irradiation to the highest dose of 600Gy. The highest SOD and GR activities were observed after irradiation to the lowest tested dose of 400Gy. This is the first study that provided basic information on the impact of gamma radiation on physiological responses of sainfoin and its radiosensitivity. These findings will be useful in development of a mutation breeding program of sainfoin.

Citrulline is an important biochemical indicator in tolerance to saline and drought stresses in melon.

Salt- and drought-induced alterations in citrulline were assessed in 4 local melon genotypes, 2 sensitive (CU-52, CU-94) and 2 tolerant (CU-196, CU-280), grown in vermiculite in a growth chamber. Salt and drought stresses were started using 30-day-old plants, with 250 mM NaCl and 45 mM PEG (-1.0 MPa) and continued for 12 days. After 12 days under salt and drought conditions, the citrulline contents were increased in the tolerant CU 196 to 25.10 µ mol gDW⁻¹ and 24.10 µ mol gDW⁻¹ for salt and drought stresses, respectively. However, the citrulline contents of the sensitive CU-52 were 11.68 µ mol gDW⁻¹ and 11.76 µ mol gDW⁻¹ for salt and drought, respectively. The striking alteration was obtained in the citrulline accumulation. The tolerant melons accumulated 2 times more citrulline than the sensitive melons. For assessing or screening melon genotypes in a large number of accessions or breeding lines for their tolerance to salinity and drought during their young plant stage, the amount of citrulline accumulation in response to the given treatments might be considered as a novel biochemical indicator of interest in early selection studies.