Abscisic acid-induced response of Triticum aestivum and T. spelta phytohormonal system to moderate soil drought

The effect of abscisic acid (ABA) priming (10 −6 M) on the growth and hormonal homeostasis of winter wheat ( Triticum aestivum L.) and spelt wheat ( T. spelta L.) plants after drought stress was analysed. During the experiment, 18-day-old water-germinated (C-plants) and ABA-primed (ABA + -plants) plants exposed to drought stress (4 days without irrigation) and 21-day-old plants after recovery were studied. Drought-stressed ABA + -plants showed increased length, fresh (FW) and dry (DW) weight of roots and decreased shoot height and FW compared to C-plants. Priming with ABA increased the accumulation of ABA in T. aestivum and T. spelta plants during soil drought. However, in T. spelta ABA + -plants, the ABA content was 2.2-fold greater than in T. aestivum . After recovery, the ABA content in both species decreased. Drought stress decreased indole acetic acid (IAA) content in T. aestivum ABA + -plants but increased in T. spelta ones. The IAA content in stressed ABA + -plants of both species was 1.6-fold higher compared to stressed C-plants. After recovery, IAA accumulated in both ABA + -plants. In stressed T. aestivum and T. spelta ABA + -plants, gibberellic acid (GA 3 ) content was 123.4% and 24.2% higher compared to C-plants. In recovered ABA + -plants, GA 3 content was higher than in C-plants. The content of salicylic acid (SA) in stressed T. aestivum and T. spelta ABA + -plants increased by 5.5% and 62.8%, respectively. Total cytokinin (CK) content in stressed T. aestivum and T. spelta ABA + -plants did not recover the level of stressed С-plants and after recovery was lower by 43% and 56.8%, respectively. Changes in CK forms in all treatments of the experiment were observed. Overall, the priming of T. aestivum and T. spelta seeds with ABA improved root growth and was associated with changes in the hormonal system of soil drought-stressed plants. The results of the experiment suggest that long-term changes in the balance of endogenous phytohormones caused by the ABA priming are related with the formation of drought stress response.