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The use of herbicides is а traditional method for weed control in crop-producing systems. Along with the high effective weed control, herbicides might cause phytotoxicity for crop plants, due to insufficient herbicide selectivity, combining herbicide treatment with unsuitable meteorological conditions, long-term persistence of herbicide in the soil or off-target transfer of the herbicide – drift. Imazamox is a selective herbicide of imidazolinone group, used to control annual and perennial weeds in imidazolinone-resistant (IMI-R) crops. Protein hydrolysates (PHs) are a group of plant biostimulants containing small peptides and free amino acids, reported to ameliorate plant abiotic stress tolerance, including herbicide phytotoxicity. This report evaluates the damaging effect of simulated imazamox drift on growth, photosynthetic performance and productivity of maize plants as well as the efficiency of foliar application by protein hydrolysates as therapy means. The received results demonstrated that the simulated imazamox herbicide drift has a strong inhibiting effect on maize plants. This is well illustrated by the retarded growth of maize plants, their disrupted photosynthetic activity and productivity losses. The foliar supply of PHs to imazamox damaged maize plants ameliorates their photosynthetic performance, growth and crop productivity., Използването на хербициди е традиционен метод за контрол на плевелната растителност при полски култури. Наред с високоефективния контрол на плевелите, хербицидите могат да причинят фитотоксичност при културните растения поради недостатъчна селективност, третиране при неподходящи метеорологични условия, остатъчни количества в почвата или при отлитане хербицида извън целевата култура – хербициден дрифт. Имазамоксът е селективен хербицид от групата на имидазолиноните, прилаган за контрол на едногодишни и многогодишни плевели в комбинация с устойчиви хибриди (IMI-R). Протеиновите хидролизати (PHs) са група растителни биостимуланти, съдържащи малки пептиди и/или свободни аминокиселини, за които е известно, че подобряват толерантността на растенията към абиотичен стрес, включително хербицидна фитотоксичност. Настоящото проучване има за цел да установи ефекта на симулиран дрифт на хербицида имазамокс върху растежа, фотосинтетичната активност и продуктивността на царевични растения, както и да оцени ефективността на листното приложени биостимуланти от групата на протеиновите хидролизати като терапевтично средство. Получените резултати показват, че симулираният хербициден дрифт оказва силен инхибиращ ефект върху царевичните растения. Това се вижда ясно от потиснатия растеж на царевичните растения, нарушената им фотосинтетичната активност и загубата на продуктивност. Листното прилагане на протеинови хидролизати върху увредените от имазамокс царевични растения подобрява фотосинтетичната им активност, растежа и продуктивността на културата.

Imidazolinone herbicides are widely used in agriculture. In some cases, they may be very persistent in soils, generating risks for the next crop in crop rotation. In several plant species, glutathione S-transferases (GSTs) take part in the detoxification of imazamox, but there exist no reports about their activity in wheat. Our study evaluated the effects of the imbibition of wheat seeds in imazamox containing solutions (10, 25 and 50 μM) on seedling growth, protein content as well as on the activity of GSTs. Growth of the young wheat seedlings was significantly inhibited after imbibition of the seeds in imazamox containing solutions. The protein content of both roots and shoots was lower compared to controls. This was partially due to a lower acetohydroxy acid synthase (AHAS) activity, leading to slowed protein turnover. The GSTs activity, determined using two different substrates 1-Chloro-2,4-dinitrobenzene (CDNB) and p-nitrophenyl acetate (pNPA), was enhanced, indicating their possible participation in cellular defence mechanisms against imazamox. The obtained new information about GSTs will be further verified in our subsequent studie

Sunflower is an economically important oilseed crop worldwide and weeds have a negative effect on its yields. The herbicide imazamox, combined with imazamox-resistant (IMI-R) sunflower hybrids, is a technology known as the Clearfield production system and successfully controls weeds. The mechanism of action of the herbicide imazamox is related to blocking the AHAS enzyme, which catalyzes the first step in the biosynthetic pathway of the branched-chain amino acids (BCAA). In the present study, we investigated the effect of the supplementary addition of BCAA to imazamox-treated IMI-R sunflower plants and antioxidative metabolism. Our results showed that the additional application of BCAA has a beneficial effect on both the total protein content and the activity of the antioxidant defense system of plants. This amelioration is probably a secondary effect of the enhanced protein metabolism and the supposed direct involvement of the three amino acids in the overall protein turnover.

The plant biostimulants (PBs) are a wide range of microbial and/or organic compounds applied to crops to improve the physiological processes such as nutrition efficiency, plant development and abiotic stress tolerance. Imazamox is a herbicide characterised with a wide spectrum of weed control, low application rates and low mammalian toxicity, but also with a high soil persistence. Therefore, the residual amounts of imazamox may negatively affect subsequent sensitive crops in the crop rotation. In the current study we investigated the effect of a single and combined treatment with imazamox and a plant biostimulant (protein hydrolisate) on the antioxidative defense system and the detoxification metabolism of wheat young plants. The result showed that the seed imbibition with 10 μM imazamox inhibits the growth of the young wheat plants. A slight improvement was found due to the additional treatment with protein hydrolysate of the wheat plants damaged by imazamox herbicide. According to the results, this improving effect on the growth does not ameliorate the plant detoxification metabolism such as glutathione S-transferases or antioxidative defense. However, the improving effect is low and insufficient to restore the plant growth and functioning and its effects on wheat production are not studied yet.

weed species. The Clearfield® technology in sunflower has been developed to allow the use of imidazolinone herbicides as a post-emergence weed control option. The Clearfield hybrids are tolerant to imazamox, aherbicide of the imidazolinone group with the trade name Pulsar 40, produced by the BASF Chemical Company. However, after imazamox treatment a temporary yellowing of the meristem tissue of the sunflower leaves is observed. The herbicidal stress increases in combination withun suitable weather conditions such as long term high temperatures and drought. The aim of the study was to examine the response of Clearfield sunflower hybrids to higher doses of the imazamox herbicide. Five hybrids were examined: LG 56.58, Tektonic, Alego, Meldimi andPrimis. The doses of imazamox treatment were as follows: non-treated control,the recommendable dose of imazamox (4.8 g a.i./da= 120 ml /da Pulsar 40) and doubled imazamox doses (9.6 g a.i. / da = 240 ml/da Pulsar 40). Treatment with the herbicide was done at 4th-6th-leave stage. The biometric and photosynthetic analyzes were carried out after the treatment. The photosynthetic leaf gas exchange, quantum yield of PSII photochemistry and growth parameters (height, fresh weight and leaf area) were determined. The obtained results showed that the treatment with the recommendable dose of imazamox caused a temporary negative impact on the photosynthetic performance and growth of the sunflower plants, which recovered after 14 days.The doubled dose of imazamox seriously damaged the existing top leaves of the sunflower plants, but the newly developed leaves were without toxicity symptoms. The studied sunflower cultivars expressed good tolerance to imazamox, applied in the recommendable dose.