Functioning of the antioxidant and osmoprotective systems of Triticum aestivum cultivars growing under soil drought conditions

In recent decades, the frequency of autumn droughts has increased in the southern and eastern regions of Ukraine and many other countries. This has negatively affected the growth of winter cereal crops, including wheat, during the early stages of development. We studied the response to soil drought in five- to nine-day-old plants of seven cultivars of Triticum aestivum L. (bread wheat) of different ecological and geographical origins. Under drought conditions, cultivars with low and medium drought tolerance showed signs of oxidative stress and a decrease in chlorophyll content. In resistant cultivars, leaf sugar content increased under drought conditions, while in non-resistant cultivars, sugar content decreased or did not change. Superoxide dismutase activity decreased in all cultivars, with a much stronger decrease observed in non-tolerant cultivars. Guaiacol peroxidase activity remained stable in drought-tolerant cultivars under stress conditions, but significantly decreased in cultivars with low and medium tolerance. A strong positive correlation was found between plant growth inhibition and the content of malonic dialdehyde, a marker of oxidative stress. Conversely, a high negative correlation was observed between growth inhibition and stress-induced changes in superoxide dismutase activity and sugar content. No significant correlation was found between growth parameters and proline and anthocyanin content changes. The contribution of components of stress protection systems to the manifestation of drought tolerance in wheat cultivars and possible functional relationships between them are discussed. Keywords antioxidant enzymes, drought tolerance, growth, proline, sugars, water deficit, wheat