Document Type : Research Paper
Authors
1 DEPARTMENT of agriculture
2 Department of Horticultural Science, Tabriz Branch, Islamic Azad University
Abstract
Background and objectives: Auxin and nano-humic acid are among the vital compounds for improving the growth and performance of plants, especially medicinal plants. Auxins are plant hormones that play a role in plant growth and development processes, including rooting, stem elongation, and regulating responses to environmental conditions. These hormones help regulate hormonal balance in plants and can help increase the quality and quantity of plant products. Nano-humic acid is also an organic compound that is obtained from the decomposition of organic matter in the soil and, due to its nano-sized dimensions, has better absorption capacity in plants. This compound helps improve soil properties, increase water retention capacity, facilitate nutrient absorption, and strengthen the plant's defense system. The use of nano-humic acid in combination with auxin can have positive effects on the growth and quality of medicinal plants, including increasing the content of active pharmaceutical ingredients. Therefore, this study investigated the effect of auxin hormone and nano-humic acid on the physiological and morphological characteristics of the medicinal plant Valerian.
Methodology: The treatments included different concentrations of auxin (0, 15, 30, and 45 ppm) and different concentrations of nano-humic acid (2, 4, and 6 g/l). Both treatments were applied as a foliar spray. This study was conducted in two years as a split-plot in a randomized block design. The dry weight of roots and shoots, and the content of auxin, cytokinin, and carbohydrates in roots and shoots were measured.
Results: In this study, the effect of auxin hormone and nano-humic acid on the physiological and morphological characteristics of the medicinal plant Valerian was investigated. The results showed that the application of auxin at concentrations of 30 and 45 ppm significantly increased the dry weight of leaves, so that in the first year, foliar spraying of auxin at a concentration of 30 ppm increased the dry weight of leaves by 15.1%, and in the second year, this increase reached 40%. Furthermore, in nano-humic acid treatments, foliar spraying at a concentration of 6 g/L significantly increased the dry weight of leaves, and it increased by 12.8% compared to not using nano-humic acid. The effect of auxin hormone also increased the chlorophyll content index, so that in the treatment with a concentration of 30 ppm, this index increased by 13.9%. In addition, the use of nano-humic acid at a concentration of 6 g/L also increased the chlorophyll index of leaves by 8%. Regarding root growth, the application of auxin, especially at concentrations of 30 and 45 ppm, increased the dry weight of roots by 33 to 39%, and nano-humic acid at a concentration of 6 g/L increased the dry weight of roots by 19.1%. Moreover, both auxin and nano-humic acid treatments increased the content of soluble sugars in leaves and roots, by 21.7% in the case of nano-humic treatment and by 14.6% in the case of auxin treatment.
Conclusion: In general, the results of this study showed that both auxin and nano-humic acid compounds, by affecting the hormonal and metabolic processes of the plant, can significantly enhance the growth and yield of medicinal plants such as valerian and increase the indices of chlorophyll, soluble sugars, and root growth. Both auxin and nano-humic acid treatments enhance leaf and root growth and increase the yield of the medicinal plant valerian by increasing photosynthetic capacity, cytokinin content, and plant source power.
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