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Abstract
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Environmental conditions and ecological factors play a significant role in the growth and performance of medicinal plants, which is the main factor in determining how plants adapt to environmental conditions. Climate change and the increasing light intensity and temperature has resulted in a decrease in water resources in field conditions, thus, plants become stressed. Plants are usually exposed to a combination of different abiotic stresses at different stages of their growth. The simultaneous occurrence of these environmental stresses is one of the most important factors affecting growth, performance, and quality of aromatic and medicinal plants, which affects the morphological state of the plants, especially those that flower, by disrupting the balance of the factors within the plant, and a flowering branch is one of the most important determinants of yield and quality for medicinal and aromatic plants. Among the Lamiaceae family, peppermint (Mentha × piperita) is the most important aromatic plant. For this purpose, a split plot experiment was studied in three replications using a random complete block design in two years to examine the effects of different levels of irrigation regimes on the number of flowering branches in peppermint under different light intensities. Experimental treatments included levels of different intensities of light (control (full sunlight), 75% sunlight and 50% sunlight) as the main factor and irrigation levels including the control (irrigation after depleting 25% of the field capacity (FC)), moderate stress (irrigation after 50% FC) and severe stress (irrigation after 75% of FC) as second factors. The results showed that, in the first year, the most flowering branches were obtained in the treatment without drought stress under 50% sunlight intensity (19.66 per plant) and in the second year and the average of two years, without water stress and under full sunlight intensity (24.33 per plant). While the lowest number of flowering branche
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