Investigation of Photosynthesis, Growth, and Water Use Efficiency of Licorice (Glycyrrhiza glabra L.) Plant Affected by Gibberellic Acid Priming and Mycorrhiza Inoculation under Water-Limited Conditions

Licorice (Glycyrrhiza glabra L.) is an important medicinal plant as it accumulates active ingredients, glycyrrhizin and liquiritin, in its roots. In the present study, mycorrhizal fungus inoculation (no inoculation and inoculation with Funneliformis mosseae) and gibberellic acid (GA) priming (no priming and priming with 1000 mg L-1) effects on growth, photosynthesis, and different characteristics of licorice root under different water regimes (100% of field capacity (FC), 65% FC, and 30% FC) were investigated. The results showed that among different irrigation levels, only the application of 30% FC led to a significant decrease in the shoot morphological characteristics, leaf chlorophyll content (SPAD), shoot dry weight, transpiration rate, net photosynthesis rate, and root length. While the application of 65% FC not only showed no significant decrease in most of the mentioned characteristics compared with 100% FC but also improved the photosynthesis parameters. Priming with GA at the 30% FC led to an improvement in photosynthetic water use efficiency compared to no pre-treatment. Also, GA increased plant height and root length, especially in combination with mycorrhizal inoculation. Inoculation with mycorrhiza improved chlorophyll content, shoot dry weight, and photosynthesis rate. Also, inoculation with mycorrhiza under 100% FC and 30% FC improved photosynthesis and photosynthetic water use efficiency. Inoculation with mycorrhiza also under 100% irrigation, and the integrated application of mycorrhiza inoculation and GA priming in 60% FC caused a significant increase in leaf area, root volume, root yield, and agricultural water use efficiency. Such results can be used in developing and promoting licorice cultivation based on water availability.