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The present work aims to alleviate the impact of drought on flax by priming seeds in folic acid. Drought was applied in pots after 24 days from sowing, and one set of samples were collected up to the 56th day for the determination of growth parameters, malondialdehyde (MDA), H2O2, ascorbate (AsA) and glutathione (GSH), photosynthetic pigments, proteins, proline, sugars, and the activities of catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione peroxidase (GPX) and ribulose-1,5-P carboxylase/oxygenase (Rubisco). The other set was collected at seed maturity for measurements of oil yield and fatty acid composition. Drought significantly decreased growth parameters, photosynthetic pigments, proteins, AsA, GSH and the activities of CAT, APX, GR, GPX and Rubisco, but raised MDA and H2O2, soluble sugars and proline concentrations. Seed priming with folic acid alleviated the impact of drought on the tested parameters. Priming raised antioxidant level and lowered oxidative stress indices pointing to an efficient antioxidant system for scavenging of free radicles. As concerns the yield analysis, there was a reduction of the number of capsules and seeds, oil quantity and quality (fatty acid concentrations and composition). Folic acid also mitigated the decreases in the number of both capsules and seeds within capsules as well as the oil and fatty acid contents and composition. Priming resulted in a recovery in the unsaturated fatty acid level causing an improvement of the oil yield quality. The results suggest that folic acid overcame the impact of drought ameliorating the oil yield and its quality features. [ABSTRACT FROM AUTHOR]

The toxicity of rimsulfuron (Rim) on acetohydroxyacide synthase (AHAS), nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), catalase (CAT) and ascorbate peroxidase (APX) in maize was evaluated examining their kinetic parameters in vitro on second leaves of 10-day-old maize seedlings. Data showed that Rim decreased Vmax and Kcat of AHAS without changing Km; on the contrary, Vmax and Kcat of the other enzymes were unchanged while Km increased. The lowest ICSO value was found for AHAS and the highest for GOGAT. Application of Rim to 10-day-old seedlings significantly inhibited the activities of all enzymes over the next 10 days besides reducing growth, proteins, amino acids, ascorbate (ASA) and glutathione (GSH). Malondialdehyde (MDA), H2O2 and oxidized glutathione (GSSG) were instead increased. Priming of grains with branched-chain amino acids [valine, isoleucine and leucine (VIL)] or dressing with naphthalic anhydride (NA) mitigated these effects. These findings suggest that Rim caused non-competitive inhibition with AHAS due to the decreased Vmax and unchanged Km; however, the enhanced Km of the other enzymes with unchanged Vmax shows an induction of competitive inhibition. Moreover, decreases of amino acids, especially branched-chain acids, and activities of NR, NiR, GS, and GOGAT could have delayed N incorporation into proteins, thus slowing their formation. The decreases of ASA, GSH, CAT, and APX concurrent with the increase of MDA and H2O2 support the induction of oxidative stress. Application of VIL or NA can protect maize from Rim causing an attenuation of the phytotoxic effects of the herbicide and enhancing maize tolerance by compensating endogenous amino acid levels, ROS homeostasis and/or herbicide detoxification. [ABSTRACT FROM AUTHOR]

This work aimed at mitigating imazethapyr (Imz) toxicity by naphthalic anhydride (NA) and to what extent it is safe to use it while applying 1-aminobenzotriazole (ABT). Ten-day-old maize seedlings, grown from grains coated with NA (0.4% w/w by seed weight), were treated with Imz, ABT or their combination. After five days, Imz reduced growth parameters, proteins, branched-chain amino acids, glutathione (GSH) and ascorbate (AsA), and activities of acetohydroxyacid synthase (AHAS), nitrate reductase/nitrite reductase (NR/NiR), glutamine synthetase/glutamate synthase (GS/GOGAT) and catalase/ ascorbate peroxidase (CAT/APX). On the contrary, peroxides and H2O2 were increased. Coating with NA reduced the herbicide residues and alleviated its impact. However, ABT raised the herbicide persistence and caused synergism for which NA became no longer effective in the presence of ABT. Imz decreased the Vmax of all enzymes but did not change their Km, except for the increase found for AHAS. The changes in both AHAS activity and the branched-chain amino acids were highly correlated. These findings suggest that Imz is a mixed inhibitor for AHAS but a non-competitive one for the other enzymes. The decrease of proteins was due to the inhibition of branched-chain amino acids and GS/ GOGAT activities. The antagonism by NA could result from enhancing herbicide detoxification, while the synergism by ABT could result from lengthening the herbicide persistence. [ABSTRACT FROM AUTHOR]