Impact of moderate soil drought on the dynamics and distribution of low molecular weight protectors in Triticum aestivum and Triticum spelta

Osmotic regulation, which involves low molecular weight protectors like amino acids and phenolic compounds, is one mechanism by which agricultural crops adapt to drought. We investigated the impact of moderate soil drought on the dynamics and distribution of free amino acids, phenols, and flavonoids in 18-day-old drought-resistant plants of Triticum aestivum L. cv. 'Podolyanka' and ecologically versatile Triticum spelta L. cv. 'Frankencorn'. Moderate soil drought resulted in a 20% increase in the total free amino acid content in spelt wheat shoots, while winter wheat exhibited minimal changes. Spelt wheat shoots showed significant increases in arginine, proline, phenylalanine, cysteine, and valine, whereas winter wheat exhibited substantial increases only in phenylalanine and tyrosine. Winter wheat shoots experienced notable decreases in arginine and glutamic acid, while methionine content in spelt wheat shoots decreased. Moderate soil drought induced an increase in the accumulation of total phenols and flavonoids. Spelt wheat roots showed a substantial increase in total phenols (53%), while winter wheat exhibited a significant increase (49%) in total phenols in shoots. Total flavonoid content increased in spelt wheat shoots and roots by 17%, and 38%, respectively, under moderate soil drought, whereas in winter wheat the increase was 70% in shootsand 10% in roots. Our findings on amino acid content suggest different sensitivities of cultivars to drought stress. The moderate increase in total phenolic compounds in spelt wheat shoots underscores the sensitivity of young T. spelta cv. 'Frankenkorn' plants to water deficit, contrasting with the more drought-resistant properties observed in T. aestivum cv. 'Podolyanka'.