Physiological responses of Pea plants to treatment with synthetic auxins and auxin-type herbicide

Abstract

The effect of exogenously applied 2,4-D (2,4-dichlorophenoxyacetic acid) on growth and antioxidant defence of pea plants, preliminary treated with two synthetic auxin compounds 1-[2-chloroethoxycarbonyl-methyl]-4-naphthalenesulfonic acid calcium salt (TA-12) and 1-[2-dimethylaminoethoxycarbonylmethyl]naphthalene chlormethylate (TA-14) was examined. All chemicals were applied by foliar spraying. Applied alone, TA-12 and TA-14 had no significant effects, but they modulated the 2,4-D induced changes on most investigated biochemical parameters. The shoot fresh weight reduction caused by 2,4-D was partially overcome by the use of TAs. The use of TAs partially overcame the shoot fresh weight reduction induced by 2,4-D. Apart from this, no significant changes were observed in the other biometric parameters. Treatment with 2,4-D did not enhance lipid peroxidation, and hydrogen peroxide content was slightly increased. These data indicate that treatment with 2,4-D did not cause severe oxidative stress, which is also confirmed by the results of the antioxidant defence system. The application of 2,4-D provoked mild accumulation of thiol-containing compounds, free proline and phenolic compounds and increased the antioxidant enzyme activities (GST, SOD, CAT, POD and GR) to a moderate degree. Pretreatment with TAs noticeably decreased the non-enzymatic antioxidants (free proline, total phenolics and total low-molecular thiols) compared to plants treated with 2,4-D only. Except for GR, TAs pretreatment returned the enzyme activities to levels close to the controls. Based on the results obtained, we suggest that the application of both synthetic auxins could modulate 2,4-D herbicide effects.

The Physiological Responses of Wheat and Maize Seedlings Grown under Water Deficit Are Modulated by Pre-Application of Auxin-Type Plant Growth Regulators

“…The slight induction of the fresh weight after application of TAs is not surprising as auxin is known to be involved in various cellular and plant growth processes [ 25 ]. In a previous study on Pisum sativum L., TA-12 and TA-14 were found to increase the growth of pea [ 13 , 14 , 18 ]. PEG causes growth inhibition as it was already reported [ 16 , 26 , 27 ].…”

“…The synthetic auxins 1-[2-chloroethoxycarbonyl-methyl]-4-naphthalenesulfonic acid calcium salt (TA-12) and 1-[2-dimethylaminoethoxicarbonylmethyl] naphthalenechlormethylate (TA-14) used in the current study are structural analogues of naphthyl acetic acid. They were previously analyzed as prospected protectors against different abiotic stress factors—cold stress in rapeseed [ 11 , 12 ]; UV-B and UV-C irradiation [ 13 , 14 ]; high temperature [ 15 ]; drought stress [ 16 ]; and as modulators of herbicidal stress [ 17 , 18 ] in pea plants.…”

The nexus between reactive oxygen species and the mechanism of action of herbicides

“…A slight increase in CAT activity in root treatments of pea plants treated with 2,4-D, but no observed difference in foliar treatments have been reported. This is accompanied by an overall increase in SOD, GPOX, APOX, GR, GST, xanthine oxidase, glucose 6-phosphate dehydrogenase, and isocitrate dehydrogenase activity in both foliar and root treatments of pea plants and little to no observed change in glycolate oxidase and hydroxypyruvate reductase activity ( 163 , 164 , 165 ). These increases in antioxidative activity do not support the idea that auxin mimicry directly affects antioxidative machinery in plant cells.…”

“…As a result of 2,4-D treatment, the antioxidant enzyme machinery of plant cells remains mostly unaffected, while there is still accumulation of ROS produced by the proposed mechanism of the impaired actin cytoskeleton. Treatment of plants by 2,4-D increases intraperoxisomal H 2 O 2 concentrations, and high accumulation was observed in the vascular tissues, central vein, and peripheral areas ( 157 , 162 , 163 , 164 , 165 , 166 ). 2,4-D treatment also increased peroxisomal membrane O 2 •− under foliar and root treatments of 2,4-D ( 164 ).…”

“…2,4-D treatment also increased peroxisomal membrane O 2 •− under foliar and root treatments of 2,4-D ( 164 ). Mutant plants for impaired ACOX 1 did not accumulate H 2 O 2 ( 165 ), with ACOX suggested as a major source of ROS under 2,4-D ( 162 ). As a major indicator of oxidative stress, lipid peroxidation plays an important role in our understanding of oxidative stress in this herbicidal group.…”