Abstract Currently, the physiological and biochemical role of certain groups of phenols with high biological activity remains poorly understood. For instance, the functions of hydroxycinnamic acids belonging to the phenylpropanoids (caffeic acid (CA), in particular) have not been fully elucidated. The goal of this research was to study the effect of different concentrations of caffeic acid on barley productivity both under normal plant development conditions and salt stress. In a series of laboratory experiments using various test crops, as well as in a greenhouse pot experiment with spring barley plants (Hordeum vulgare L.), the effect of caffeic acid was investigated. The activity of different concentrations of caffeic acid was determined using several plant bioassay approaches: a rapid method in Petri dishes, an applicative method in plastic tablets, and a method involving plant growth in aqueous solutions. The greenhouse experiment was conducted on gray forest medium loamy soil with an organic matter content of 3.8% and a slightly acidic soil solution reaction (pHKCl 5.9). A NaCl solution (7.5 g L‒1) was added at the stage of the second or third leaf. Plants received a single foliar treatment with caffeic acid during the tillering phase. Based on the results of preliminary laboratory experiments, three concentrations of CA were used in the experiment: 100, 50, and 10 μM. At the beginning of the stem elongation stage, barley plants were harvested and soil samples were collected. In the dry plant mass, the contents of potassium, sodium, and total nitrogen were determined. To measure the chlorophyll and carotenoids contents, the flag leaf of the plants was used. According to the results of plant bioassays, the greatest activity for both monocotyledonous and dicotyledonous crops was observed at the lowest CA concentrations (10 and 25 μM), whereas higher CA concentrations (50 and 100 μM) significantly decreased all test indicators. Based on the results of the greenhouse experiment, it was established that caffeic acid did not reliably display a stimulating effect. Under sodium chloride salinity, using the highest CA concentration (100 μM) led to a slight increase in soil potassium content. Meanwhile, the soil sodium content decreased with CA use. The total plant weight per pot significantly decreased from 1.25 to 0.25 g/pot. Without NaCl, CA treatment did not significantly change the barley weight. Chlorophyll (a and b) content in the control variant (1.83 mg g‒1) was significantly lower compared to leaves treated with CA: 4.03 mg g‒1 at 10 μM CA and 3.14 mg g‒1 at 100 μM CA. Against the NaCl background, the total chlorophyll content decreased to 0.24 mg g‒1; however, CA treatment increased it from 1.26 mg g‒1 (at 10 μM) up to 2.14 mg g‒1 (at 100 μM). Using CA at a concentration of 100 μM was also accompanied by an increase in carotenoids content from 0.22 to 0.61 mg g‒1 and, under salinity, from 0.16 to 0.38 mg g‒1. Thus, the use of CA for plant treatment during the growing season under salinity conditions affects physiological processes, supporting plant adaptation.

Role of Exogenous Effect of Caffeic Acid on Barley Plants

期刊论文
发表日期：

2025年6月1日

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M. M. Akishina,
L. P. Voronina

摘要

Abstract

Currently, the physiological and biochemical role of certain groups of phenols with high biological activity remains poorly understood. For instance, the functions of hydroxycinnamic acids belonging to the phenylpropanoids (caffeic acid (CA), in particular) have not been fully elucidated. The goal of this research was to study the effect of different concentrations of caffeic acid on barley productivity both under normal plant development conditions and salt stress. In a series of laboratory experiments using various test crops, as well as in a greenhouse pot experiment with spring barley plants (Hordeum vulgare L.), the effect of caffeic acid was investigated. The activity of different concentrations of caffeic acid was determined using several plant bioassay approaches: a rapid method in Petri dishes, an applicative method in plastic tablets, and a method involving plant growth in aqueous solutions. The greenhouse experiment was conducted on gray forest medium loamy soil with an organic matter content of 3.8% and a slightly acidic soil solution reaction (pH_KCl 5.9). A NaCl solution (7.5 g L^‒1) was added at the stage of the second or third leaf. Plants received a single foliar treatment with caffeic acid during the tillering phase. Based on the results of preliminary laboratory experiments, three concentrations of CA were used in the experiment: 100, 50, and 10 μM. At the beginning of the stem elongation stage, barley plants were harvested and soil samples were collected. In the dry plant mass, the contents of potassium, sodium, and total nitrogen were determined. To measure the chlorophyll and carotenoids contents, the flag leaf of the plants was used. According to the results of plant bioassays, the greatest activity for both monocotyledonous and dicotyledonous crops was observed at the lowest CA concentrations (10 and 25 μM), whereas higher CA concentrations (50 and 100 μM) significantly decreased all test indicators. Based on the results of the greenhouse experiment, it was established that caffeic acid did not reliably display a stimulating effect. Under sodium chloride salinity, using the highest CA concentration (100 μM) led to a slight increase in soil potassium content. Meanwhile, the soil sodium content decreased with CA use. The total plant weight per pot significantly decreased from 1.25 to 0.25 g/pot. Without NaCl, CA treatment did not significantly change the barley weight. Chlorophyll (a and b) content in the control variant (1.83 mg g^‒1) was significantly lower compared to leaves treated with CA: 4.03 mg g^‒1 at 10 μM CA and 3.14 mg g^‒1 at 100 μM CA. Against the NaCl background, the total chlorophyll content decreased to 0.24 mg g^‒1; however, CA treatment increased it from 1.26 mg g^‒1 (at 10 μM) up to 2.14 mg g^‒1 (at 100 μM). Using CA at a concentration of 100 μM was also accompanied by an increase in carotenoids content from 0.22 to 0.61 mg g^‒1 and, under salinity, from 0.16 to 0.38 mg g^‒1. Thus, the use of CA for plant treatment during the growing season under salinity conditions affects physiological processes, supporting plant adaptation.