Evaluation of important morpho-physiological characters of Lavandula officinalis L. affected by foliar application of elicitors

Background and objectives: Lavender is an important plants with many uses in various medicinal and food industrial. In sustainable production systems of the 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 the organic and alcoholic elicitors on the important morpho-physiological characters of L.officinalis to determine and introduce the best elicitor for increasing of qualitative and quantitative characters.

Materials and methods: This research was performed in Ben city from Chaharmahal & Bakhtyari province (latitude. 32°35′ N, longitude. 50°33′ E, altitude. 2380 m) in 2023-2024. Based on the Köppen climate classification, the climate of the area of study is classified as cold and semiarid. The present study was conducted in a randomized complete block design (RCBD) with three replications to investigate the effect of foliar application of different elicitors. Seedlings with 4-6 leaf in first year were sown at 4 May 2023 and in second year, planted at 9 May 2024 and irrigated immediately. Treatments contain of organic elicitors such as chitosan (0.25 and 0.50 gr.L-1), salicylic acid (1.5 and 3 mM) and phenylalanine (1000 and 2000 mg. L-1), alcoholic elicitors such as ethanol, methanol and acetone (10% and 20%), water spraying and control level (without any spraying). Estimated morphological characters were shoot dry/fresh matter, height of plant, number nod per stem and number stem per plant; and physiological characters were content of chlorophyll a, chlorophyll b and total chlorophyll, carotenoid, antioxidant and flavonoid. In each year, treatments were applied in 3 stage (early vegetative phase (20-25 leaf), 50% vegetative phase (150-200 leaf) and beginning of flowering) and harvesting were done in complete flowering at 5 July 2023 in first year and 9 July 2024 in second year.

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 of morphological characters such as shoot fresh matter (144.37 g.plant-1), shoot dry matter (67.46 g.plant-1), height of plant (66.57 Cm) in treatment of chitosan 0.25 gr.L-1, number stem per plant (45.78) in treatment of phenylalanine 1000 mg. L-1 and the highest number nod per stem (28.62) in treatment of ethanol (10%) and the least amount of shoot fresh matter (51.56 g.plant-1), shoot dry matter (21.14 g.plant-1), height of plant (25.18 Cm), number nod per stem (12.14) and number stem per plant (25.99) made by water foliar application and control plants. Also the most measured physiological characters such as chlorophyll a (2.34 mg.g-1 FW) in treatment of chitosan 0.5 gr.L-1, chlorophyll b (0.91 mg.g-1 FW), total chlorophyll (3.06 mg.g-1 FW) in treatments of chitosan 0.5 gr.L-1 and salicylic acid 1.5 mM, the amount of antioxidant (79.00 mg.gr-1 FW), flavonoid (691.03 mg.gr-1 FW) in treatment of chitosan 0.25 g.L-1 and carotenoid (2.89 mg.gr-1 FW) in salicylic acid 1.5 mM were obtained. The least of chlorophyll a (1.52 mg.g-1 FW), chlorophyll b (0.36 mg.g-1 FW), total chlorophyll (1.88 mg.g-1 FW), the amount of antioxidant (40.00 mg.gr-1 FW), flavonoid (300.1 mg.gr-1 FW) and carotenoid (0.5 mg.gr-1 FW) in treatments of water foliar application and control were made.

Conclusion: The application of organic elicitors (chitosan and phenylalanine) and alcoholic elicitors (ethanol and methanol) made significant effectiveness on morpho-physiological characters of Lavender. Use of elicitors of chitosan (0.25 gr.L-1) and phenylalanine (1000 mg.L-1) in most of characters for better nutrition were the best treatments.