Mycorrhizal inoculation mitigates drought stress in borage (Borago officinalis L.): Evidence from biochemical, physiological, and growth responses

Borage (Borago officinalis L.) is an annual medicinal plant awaiting scientific examinations of its growth, biochemical, and physiological responses to drought upon mycorrhizae inoculation. Hence, two pot experiments were conducted to shed light on the ameliorative effects of mycorrhizae ((Funneliformis mosseae) (T.H. Nicolson & Gerd.) C. Walker & A. Schuessler)) on the drought-induced alterations in different plant attributes, ranging from physiological to biochemical attributes and from root characteristics to shoot growth, and dry mass of two borage genotypes. Drought resulted in suppression of root mycorrhizal colonization, leaf chlorophyll concentration, maximum quantum efficiency of photosystem II, relative water content, P concentration, membrane stability index, plant above-ground dry mass, root dry mass and volume, and plant’s total (shoot + root) dry mass. Though, it led to increases in the leaf carotenoids/chlorophyll ratio, carotenoids, proline, soluble sugars, total phenolic content, and total flavonoids content. Mycorrhizae inoculation lessened drought penalties of leaf chlorophyll concentration, maximum quantum efficiency of photosystem II, relative water content, membrane stability index, P concentration, root volume and dry mass, plant above-ground dry mass, and plant’s total dry mass. The inoculation increased total phenolic and flavonoids contents, and carotenoids concentrations, particularly under drought stress conditions. These results underline for the first time the importance of the plant’s mycorrhizae inoculation in mitigating adverse effects of drought and enhancing the antioxidative capacities and physiological functions of this less-known medicinal plant species.