Sergei Ivanov

Alterations in glutathione pool and some related enzymes in leaves and roots of pea plants treated with the herbicide glyphosate

Our previous studies have demonstrated that application of glyphosate caused oxidative events in young pea and wheat plants. In this work, the changes in the endogenous level of glutathione (total and oxidized) and the activities of glutathione reductase (GR) and glutathione S-transferase (GST) after treatment with glyphosate were studied in pea plants (Pisum sativum L., cv. Skinado). Glyphosate was applied in two ways: (1) by leaf spraying with 10 mM solution; and (2) in nutrient medium as 0.01 mM solution. Measurements were made in both leaves and roots. Root and leaf treatments provoked the increase in both total and oxidized glutathione contents. Both types of herbicide application caused activation of GR in treated organs. Slight increase was detected also in untreated roots. It was found that glyphosate application to leaves provoked strong enhancement in the GST activity in leaves, while its root application stimulated the enzyme activity in the roots. We observed the higher GST activity in the organ directly treated with herbicide. Furthermore, we suggested that the activated isoforms of GST(s) participated in detoxification of hydrogen peroxide and lipid peroxides.

Cumulative effect of low and high atrazine concentrations on Arabidopsis thaliana plants

Atrazine belongs to the widely used herbicides blocking the electron transport chain in chloroplasts, thus resulting in the generation of active oxygen species. In the present work, we demonstrated that, at low concentrations mimicking residual amounts, atrazine enhanced the susceptibility of Arabidopsis plants to further treatments with the same herbicide applied at the recommended field rate. Arabidopsis thaliana plants were treated three times (at five-day intervals) with 1 µM atrazine. Five days after the last treatment, the plants were sprayed with 5 mM atrazine. Atrazine increased the levels of lipid peroxidation products, hydrogen peroxide, and ion leakage, and caused changes in the activities of antioxidant enzymes, such as superoxide dismutase, guaiacol peroxidase, and catalase.

Early detection of changes in leaf reflectance of pea plants (Pisum sativum L.) under herbicide action

Based on high resolution leaf spectral reflectance data a new technique was developed and applied to detect damages of agricultural plants under the action of low intensity stress factors (herbicides) which at very low concentrations could not be established by the standard biochemical and biometric techniques. Results are presented from a remote sensing study of the peculiarities of the leaf spectral reflectance of pea plants (Pisum salivum L.) treated with atrazine and 2.4-D (2.4 - phenoxyacetic acid) at three low concentrations (0.01 /spl mu/M, 0.1 /spl mu/M and 1 /spl mu/M, respectively 2.15, 21.5, and 215 /spl mu/g/l for atrazine and 2.59, 25.9, and 259 /spl mu/g/l for 2.4-D) as compared to the field dose of these herbicides commonly used in the agricultural practice. The physiological status of the plants was assessed using biometric and biochemical parameters such as length, fresh weight, dry weight and electrolyte leakage. The high-resolution spectral data were obtained using a multichannel spectrometer in the visible and near infrared ranges of the electromagnetic spectrum in 128 channels at a spectral resolution (halfwidth) of 2.6 nm. Using the technique which employs discriminant analysis and other statistical methods we established the presence of statistically significant differences in the arising variations of the leaf spectral reflectance characteristics between control and treated plants in the green (520+580 nm), red and near infrared (690+800 nm) ranges of the spectrum.

Remote Sensing Study of the Influence of Herbicides Fluridone and Acifluorfen on the Spectral Reflectance of Pea Plant Leaves (Pisum sativum L.)

Results from a remote sensing study of the leave spectral reflectance of pea plants (Pisum sativum L. cultivar Scinado) treated by the photosynthetic herbicides fluridone and acifiuorfen are presented. According to the mode of action, fluridone belongs to Fl (photobleaching) group of herbicides, and acifiuorfen -to the group E as classified by the Herbicide Resistance Action Committee. The pea plants were grown hydroponically in a growth chamber in a nutritious medium to which the herbicides were added at two low concentrations (1 muM, 0.1 muM for fluridone, and 25 muM, 2.5 muM for acifiuorfen). The high-resolution spectral data were obtained in the visible and near infrared ranges of the spectrum (450/850 nm) using a USB2000 fiber optic spectrometer at a spectral resolution (halfwidth) of 1.5 nm. After data analysis, optimal spectral intervals for evaluation of the herbicide action were specified. The changes occurring in the spectral reflectance of the pea plants were assessed in four intervals: 520/580 nm (region of maximal reflectivity of green vegetation), 640/680 nm (region of maximal leave absorption), 690/720 nm (red edge region), and 720/770 nm (near infrared region) using the t-criterion of Student and linear discriminant analysis. Statistically significant differences were found between the spectral reflectance data of leaves of control and treated with herbicides plants at a significance level p<0.05 for the two fluridone concentrations and for 25 muM concentration of acifiuorfen. The applied approach provides fast and reliable remote sensing of plant response to the environment.