State of antioxidant and osmoprotective systems in etiolated winter wheat seedlings of different cultivars due to their drought tolerance

Climatic changes bring the problem of drought tolerance of winter cereals to the fore at the earliest stages of development, immediately after autumn sowing. The reaction of antioxidant and osmoprotective systems of etiolated seedlings of winter wheat (Triticum aestivum L.) under osmotic stress was investigated. Seeds of seven cultivars were germinated for 4 days in Petri dishes on filter paper moistened with distilled water (control) or nonpenetrating osmotic agent PEG 6000 at a concentration of 12% (osmotic pressure 0.17 MPa) at 24 degrees C. After that, the mass of shoots and roots of seedlings of experimental and control treatments were determined. Biochemical parameters were also determined in the shoots of 4-day-old seedlings. The highest ability to maintain shoot growth under osmotic stress was in the 'Tobak'; it was medium in the 'Antonivka', 'Lira Odeska, and 'Darynka Kyivska', and low in the 'Bogdana', 'Doskonala', and 'Avgustina'. In the least resistant 'Doskonala' and 'Avgustina', the content of lipid peroxidation product malondialdehyde was significantly increased in the shoots under osmotic stress. In the non-resistant cultivars and, also, in the medium-resistant 'Darynka Kyivska', an increase in hydrogen peroxide content was noted under osmotic stress. High-and medium-resistant cultivars were characterised by an increase in superoxide dismutase (SOD) activity in response to osmotic stress. Also, high-and medium-resistant cultivars showed a high catalase (CAT) activity. Osmotic stress caused an increase in guaiacol peroxidase activity in all cultivars, regardless of their drought tolerance. The proline content increased to some extent in all cultivars in response to stress exposure; however, no relationship was found between the amount of proline and drought resistance. The content of sugars under osmotic stress increased only in high and medium drought-resistant cultivars. Drought-resistant cultivars were also characterised by a high base content of flavonoid compounds absorbing UV -B and their retention under osmotic stress. Under osmotic stress, the strongest correlation (p <= 0.05) was found between the resistance to osmotic stress and the SOD activity (r = 0.93) as well as the sugar content (r = 0.85). In addition, a significant correlation was found between the drought tolerance and the flavonoid content and the CAT activity in seedlings. The complex of these indicators can be used to assess the drought tolerance of various genotypes of etiolated winter wheat seedlings.