Effects of superabsorbent nano-polymer, grow-more, iron and zinc fertilizers on morpho-physiological and phytochemical properties of Lavender (Lavandula angustifolia Mill.) under drought stress

Background and objectives: Lavender from the Lamiaceae family is an important plants with many uses in various medicinal and food industrial. Among environmental stresses, water deficit stress plays an important role in the biosynthesis of secondary metabolites in medicinal plants in arid and semi-arid regions like Iran. Drought stress has detrimental effects on growth and yield and can upset the balance between the antioxidant defense system and free radicals by stimulating a series of biochemical reactions, where free radicals cause cell damage. In sustainable production systems of medicinal and aromatic plants, stable quantitative and qualitative functions can be achieved under conditions of environmental stress and it is possible to improve the production of secondary metabolites in these plants under adverse environmental conditions. Therefore, this study was done to evaluate some of important macro-micro nutrients on the morpho-physiological and phytochemical properties of Lavandula angustifolia to determine and introduce the best combinations of fertilizers with use of superabsorbent nano-polymer under water stress conditions.

Materials and methods: This research was using a randomized complete block design (RCBD) in a split-split plot layout with three replications. Irrigation regimes (D1-D3: Field Capacity, 50% and 75% evaporation from basin class A) in main plots, superabsorbent nano-polymer application (S1-S2: use and not use) in sub plots and treatments of fertilizers in sub-sub plots were done. This research was performed in farm of Islamic Azad University Branch of Shahrekord (latitude. 32°20′ N, longitude. 50°51′ E, altitude. 2061 m) in 2023-2024.

Results: Over two consecutive years, the obtained results showed that the use of treatments increased the characters and made the significant effectiveness. In two years, the highest shoot dry matter (61.55 g.plant-1), zinc of shoot (69.55 µg/g dry weight), iron of shoot (82.85 µg/g dry weight), phenol (1.39 mg.Kg Fw-1), chlorophyll content (2.92 mg.g-1 DW) and the lowest amount of prolin (10.89 µg.KgFw-1), made by grow-more fertilizers specially grow-more 1 (20-20-20) in combination with Fe/Zn Libfer. However the superabsorbent nano-polymer application had the aggressive effectiveness on amounts of characters especially in hardness of water stress. In most of measured characters, plants treated with grow-more fertilizers were in the same group. The lowest values for morpho-physiological and phytochemical characters such as shoot dry matter (22.12 g.plant-1), zinc of shoot (28.34 µg/g dry weight), iron of shoot (40.77 µg/g dry weight), phenol (0.29 mg.KgFw-1), chlorophyll content (1.95 mg.g-1 DW) and the most of prolin (32.01 µg.KgFw-1), obtained by plants treated with irrigation regime of 75% evaporation from basin class A (D3) and no application of fertilizers. In some characters, plants treated with F12, F13 or F14 treatments under hardness of drought stress had the same group with control plants. The main constituents of essential oil were Linalool, Linalyl acetate, Limonene, Alpha-pinene, 1, 8 cineole, Borneol, Camphor (alcoholic/cyclic monoterpenes) and Beta-farnesene, Alpha-bisabolene and Beta-Caryophyllene (Sesquiterpenes) that made the most components of essential oil plants. The effect of grow-more 1 (20-20-20) in combination with Fe/Zn Libfer on increasing the total phenol and chlorophyll content, were higher than the other grow-more fertilizers ones.

Conclusion: Generally the application of grow-more fertilizer 1 (20-20-20) with consumption of zinc and iron fertilizers can be a good strategy to improve the morpho-physiological and phytochemical characters of L.angustifolia especially the grow-more 1 (20-20-20) in combination with Fe/Zn Libfer in field capacity water condition. However the use of superabsorbent nano-polymer in strenuous drought stress (75%) is more effectivnes than other water stress levels. Finally, the application of grow-more 1 (20-20-20) in combination with Fe/Zn Libfer can be a good strategy to improve morpho-physiological characters and essential oil quantity and quality of L.angustifolia in cold and semi-arid climates.