Strigolactones (SLs) have been implicated in many plant biological and physiological processes, including the responses to abiotic stresses such as drought, in concert with other phytohormones. While it is now clear that exogenous SLs may help plants to survive in harsh environmental condition, the best, most effective protocols for treatment have not been defined yet, and the mechanisms of action are far from being fully understood. In the set of experiments reported here, we contrasted two application methods for treatment with a synthetic analog of SL, GR24. A number of morphometric, physiological and biochemical parameters were measured following foliar application of GR24 or application in the residual irrigation water in winter wheat plants under irrigated and drought stress conditions. Depending on the concentration and the method of GR24 application, differentiated photosynthesis and transpiration rate, stomatal conductance, leaf water potential, antioxidant enzyme activities and yield in drought conditions were observed. We present evidence that different methods of GR24 application led to increased photosynthesis and yield under stress by a combination of drought tolerance and escape factors, which should be considered for future research exploring the potential of this new family of bioactive molecules for practical applications.

Ziziphora clinopodioides L. is a valuable medicinal and aromatic plant; however, its special requirements for proper growth and enhanced secondary metabolite composition have limited its production and availability. The lack of appropriate fertilizer dosage recommendations is one of these limiting factors for ex situ conservation and large-scale cultivation. This study investigated the effects of nitrogen (N) fertilization on Z. clinopodioides in both open field and unheated greenhouse conditions. The determined research factor was N dosage (0, 40, 80, and 120 kg N ha⁻¹ in the field) and (0, 200, 400, and 600 mg N pot⁻¹ in the greenhouse). It was found that Z. clinopodioides plants could grow successfully outside their natural habitat with sufficient N fertilization yielding a satisfactory amount of metabolites per plantation area. Specifically, among the tested dosages, the 120 kg N ha⁻¹ (which showed no significant difference from 80 kg N ha⁻¹) and 400 mg N pot⁻¹ fertilizers increased the aboveground dry and fresh biomass, essential oil (EO) content, and yield. Nitrogen fertilization showed a direct correlation with menthone, neo-menthol, menthol, pulegone, E-ocimenone, and spathulenol, but a negative correlation with α-pinene, β-pinene, limonene, 1,8-cineol, trans-pulegol, and iso-menthone. This study is the first to evaluate the effects of N fertilization on the genus Ziziphora. The results indicate that utilizing N fertilizer at a moderate rate (80 kg N ha⁻¹ in the field and 400 mg N pot⁻¹ in the greenhouse) can improve the agronomic traits and EO of Z. clinopodioides.