Comparison of the Effect of Mycorrhiza Fungi, Humic Acid, and Putrescine Treatments on Lallemantia royleana under Drought Stress

The maintenance of growth and crop productivity under water deficit represents one of the main challenges of modern agriculture. In this research, the role of foliar spraying with putrescine (0, 0.5, and 1 mM), soil application of humic acid, and soil application of arbuscular mycorrhizal fungi) in reducing the negative effect of irrigation regime[full irrigation or control, stopping irrigation from the beginning of flowering (moderate drought) and the beginning of branching (severe drought) respectively] on the morphological and biochemical indicators of Balangu (Lallemantia royleana Benth. in Wall.) plants was investigated. The experiment was set up in three replications, utilizing a split-plot design based on a randomized complete block design. Moderate and severe drought levels decreased morphological parameters and leaf elements, while increasing proline, soluble carbohydrate content, reactive oxygen species, and total phenol. The use of putrescine, humic acid, and Arbuscular mycorrhizal fungi reduced the adverse effects of drought stress on plant height, fresh and dry weight, crown diameter, lateral bench number, leaf length, and width. They also increase proline and soluble carbohydrate content, which increases the plant’s resistance to stress conditions. Humic acid and Arbuscular mycorrhizal fungi increased the content of soluble carbohydrates by 30 and 22% and proline by 72 and 72% under severe drought stress conditions, while decreasing reactive oxygen species by 25 and 19%. In general, with the stopping of irrigation from the beginning of flowering, the growth characteristics of the plant decreased, but with the use of growth stimulants, the negative effects of the drought stress were moderated.