This study investigated the effects of the herbicide from the graminicide group fenoxaprop, on oat plants under a normal and reduced water supply. The study was done in vegetative experimental conditions. It was established, that plants treated with fenoxaprop after 2 days following a reduction of the water content in soil with 60% to 40% of full field moisture capacity, significantly reduced phytotoxic action. At the decreased level of water supply in the oat plants, activity of antioxidant enzymes -superoxide dismutase, and catalase increased. The fenoxaprop action did not lead to a substantial increase in superoxide anion radical and hydrogen peroxide content, which had been observed under the action of the herbicide when normal levels of water were supplied to the plants.It was concluded, that the phytotoxic action of the herbicides from the graminicide group mediated the formation of reactive oxygen species and reduction of phytotoxicity on the background effect on plants of various stressors. This reaction was due to the increased activity of antioxidant enzymes, associated with nonspecific reaction of plants to these stressors.

No abstract

З метою визначення джерел утворення супероксидного аніон-радикала (САР) досліджено активність НАДФН-оксидази у меристемах коренів проростків кукурудзи за дії гербіциду інгібітору ацетил-КоА-карбоксилази галоксифоп-R-метилу (ГФ). Встановлено, що активність НАДФН-оксидази підвищується лише на початкових етапах розвитку фітотоксичної дії гербіциду. Зроблено висновок, що окрім НАДФН-оксидази існує інше джерело утворення САР, яке зумовлює тривале збільшення вмісту цієї активної форми кисню з початку розвитку фітотоксичної дії гербіциду до моменту появи некрозів у меристемах.

The aim of this study was to test the hypothesis that pathogenesis induced in sensitive plants by ALS-and ACC-inhibiting herbicides is an active process which involves programmed cell death (PCD). A reliable marker of PCD is DNA fragmentation, which is carried out by endogenous nucleases. The root meristems from herbicide-sensitive plants were analyzed by the TUNEL assay to estimate DNA fragmentation. It was shown that the highest level of DNA fragmentation in root meristem cells under pathogenesis, induced on maize seedlings by the action of ACC-inhibiting herbicide propaquizafop, and on pea seedlings by the action of ALS-inhibiting herbicide tribenuron-methyl, was associated with increased total nuclease activity in root meristem lysates comparing to the corresponding control. In response to tribenuron-methyl application, the level of total nuclease activity elevated due to high activity of both Zn 2+ -dependent («acidic») and Ca 2+ /Mg 2+dependent («alkaline») nucleases, while in a case of propaquizafop, the increased activity was detected only for Zn 2+ -dependent nucleases. These differences may be due to different mechanisms of PCD initiation, depending on the mode of herbicides action. The facts, that TUNEL method recorded DNA fragmentation in plant cells induced by ACC-and ALS-inhibiting herbicides, and this fragmentation is associated with an increased activity of endogenous nucleases, represent evidence for PCD, that occurs during pathogenesis. The significance of data obtained is that they emphasize the fact that herbicide-induced pathogenesis is a complex, multi-stage, active process. The discovery of pathogenesis distinct stages mechanisms nature opens up new possibilities for regulating the herbicides selective phytotoxicity by physiologically active substances and genetically engineered manipulations.

Many countries are now facing the problem of increase in resistant biotypes of weeds. The spread of herbicide-resistant weeds across agrophytocenoses poses a threat of decrease in the effectiveness of use of herbicides in agricultural fields. In order to develop anti-resistant compositions of herbicides for protection of maize (Zea mays L.) crops, we studied effects of interaction and efficiency of weed control in greenhouse and field experiments. We studied the possibility of combined use of 4-hydroxyphenyl pyruvate dioxygenase-inhibiting herbicide tolpyralate and inhibitor of transport of electrons in photosystem 2 of chloroplasts – terbuthylazine – and acetolactate synthase-inhibiting rimsulfuron. In greenhouse experiments on model objects, we found that interaction in the mixtures of tolpyralate with rimsulfuron was antagonistic, but the antagonism may be overcome by increasing the rate of applied rimsulfuron. At joint use of tolpyralate and terbuthylazine, a synergistic increase in phytotoxic effect was observed, caused by increase in the effectiveness of the blocking electron-transport chain and increase in intensity of formation of reactive oxygen species. According to the results of the field experiments, we drew the conclusion that the efficacy of using the mixture of tolpyralate and rimsulfuron depends on the species composition of weeds. In the presence of rimsulfuron-resistant weeds, interaction with tolpyralate becomes antagonistic even in the conditions of increased rate of application of rimsulfuron, and thus the effectiveness of the protection significantly decreases. At the same time, after applying tank mixture of tolpyralate with terbuthylazine, the synergistic character of the interaction was maintained toward a broad range of species of grass and dicotyledonous weeds, providing high efficiency of maize crop protection. The herbicide compositions that were analyzed and are presented in the article allow one to decrease the possibility of emergence of resistant biotypes of weeds, and also to effectively control the already existing resistant biotypes.