The effect of heavy metals and thidiazuron on winter wheat (Triticum aestivum L.) seedlings

Abstract We studied the influence of a synthetic cytokinin-like growth regulator thidiazuron (TDZ) and ions of heavy metals (HMs) -Pb , and Ni 2+ on the growth, generation of superoxide anion, concentration of total peroxides, lipid peroxidation, and catalase activity in the leaves of 7-day-old winter wheat plants (Triticum aestivum L. cv. 'Mironovskaya 808'). It was found that 1 mM solution of HMs inhibited the growth of roots in the following sequence: Zn . HMs inhibited the growth of aboveground parts of young wheat plants, too. HMs stimulated superoxide production by a factor of 1.3-4.9. The content of total peroxides in wheat leaves increased in the presence of HMs in the growth medium. Our analyses showed that malonic dialdehyde (MDA) content in leaves increased with increasing Cu 2+ or Ni 2+ concentra tions in the medium and hardly changed with increasing Pb 2+ or Zn 2+ concentrations. HMs enhanced catalase activity in wheat plants 1.1-2.8-fold at all concentrations studied. All these regularities are indications of HMs-induced oxidative stress in wheat plants. In most treatments, TDZ alleviated the HMs-induced oxidative stress and promoted an increase in Wilkinson tolerance index (WTI). This suggests that the wheat seedlings treated with TDZ were more HMs-resistant than the untreated ones

An efficient antioxidant system and heavy metal exclusion from leaves make Solanum cheesmaniae more tolerant to Cu than its cultivated counterpart

Copper (Cu) is an abundant metal in the environment coming from anthropogenic activities and natural sources that, in excess, easily becomes phytotoxic to most species, being its accumulation in plants considered an environmental threat. This study aimed to compare the physiological and molecular responses of Solanum lycopersicum and its wild counterpart Solanum cheesmaniae to Cu stress. In particular, we wanted to address the hypothesis that S. cheesmaniae is more adapted to Cu stress than S. lycopersicum, since the former is equipped with a more efficient antioxidant defense system than the latter. Biomarkers of oxidative status (lipid peroxidation, hydrogen peroxide (H2O2) and superoxide anion (O.− 2 ) levels) revealed a more pronounced imbalance in the redox homeostasis in shoots of S. lycopersicum than in S. cheesmaniae in response to Cu. Furthermore, the activity of key antioxidant enzymes clearly differed in both species in response to Cu. Catalase (CAT) activity increased in S. cheesmaniae shoots but decreased in the domestic species, as well as ascorbate peroxidase (APX). Both species preferentially accumulated Cu in the radicular system, although a great increase in the aerial parts of S. lycopersicum was measured, while in leaves of Cu- treated S. cheesmaniae, the levels of Cu were not changed. Overall, results validated the hypothesis that S. cheesmaniae is more tolerant to excess Cu than S. lycopersicum and the data provided will help the development of breeding strategies toward the improvement of the resistance/tolerance of cultivated tomato species to heavy metal stress.This research was partially supported by national funds provided by Foundation for Science and Technology (FCT) through PEst-OE/BIA/UI4046/2014 (FCT through BioISI) and through the research project PTDC/ AGR-PRO/7028/2014.info:eu-repo/semantics/publishedVersio

Role of salicylic acid in acclimation to low temperature

Low temperature is one of the most important limiting factors for plant growth throughout the world. Exposure to low temperature may cause various phenotypic and physiological symptoms, and may result in oxidative stress, leading to loss of membrane integrity and to the impairment of photosynthesis and general metabolic processes. Salicylic acid (SA),phenolic compound produced by a wide range of plant species, a may participate in many physiological and metabolic reactions in plants. It has been shown that exogenous SA may provide protection against low temperature injury in various plant species, while various stress factors may also modify the synthesis and metabolism of SA. In the present review, recent results on the effects of SA and related compounds in processes leading to acclimation to low temperatures will be discussed

The effect of growth regulators on in vitro callus formation in cucumber and radish

Background.Callus culture in vitro is a convenient model for studying physiological and biochemical manifestations at the cellular level, as well as for cell selection to stress factors. To obtain a callus culture, it is necessary to select the optimal ratio of exogenous hormonal growth regulators (GRs) in the nutrient medium. The purpose of the study is to determine the optimal ratios of GRs at the stage of introducing cucumber and radish into in vitro culture. Materials and methods. Sterile plants of cucumber (Cucumis sativus L., cv. Unity) and radish (Raphanus sativus L., cv. Red Giant) were taken as the object of study. The experiment included obtaining a callus culture of cucumber and radish from various explants (cotyledon leaves, hypocotyl and roots) on a nutrient medium with a mineral base according to Murashige-Skoog supplemented by mesoinositol (100 mg/l), glycine (1 mg/l), nicotinic acid (0.5 mg/l), as well as growth regulators 2.4-dichlorophenoxyacetic acid (2.4- D) and 6-benzylaminopurine (6-BAP) in various ratios. Results. A method for introducing cucumber and radish into in vitro culture is described. The role of the hormonal composition of the nutrient medium in callusogenesis was shown, the influence of different concentrations of GRs, auxin 2.4-D and cytokinin 6-BAP, on callus formation was revealed. For various explants of cucumber and radish, the optimal concentrations of used GRs were determined. Conclusions. The optimal composition of GRs (auxin 2.4-D and cytokinin 6-BAP, mg/l) in Murashige-Skoog medium was selected for callusogenesis on various explants of cucumber (2:2) and radish (4:0.5). A higher intensity of callusogenesis in cucumber on hypocotyl explants and no dependence of callusogenesis on the type of explantin radish were revealed

Sydnone Imines: A Novel Class of Plant Growth Regulators

An increase in the yield of the main cereal crops in the context of global climate changes requires additional impacts on plants. Natural and synthetic plant growth regulators (PGRs) are used to increase plant productivity and reduce the injury level caused by abiotic stressors. There is a growing need for novel highly effective plant growth stimulants to exhibit their effects at low doses and to not pose an environmental threat or injury to the crop quality. The derivatives of sydnone imine (SI), a mesoionic heterocycle possessing a 1,2,3-oxadiazole core, have been used as medicines until now but have not been used for agricultural applications. Some SI derivatives have recently been found to exhibit PGR properties. Herein, we report on the study of the PGR potential of nine SI derivatives bearing variable substituents at N(3), C(4), and N6 positions of the heterocycle designed to disclose the “molecular structure-PGR activity” relationship in this family. The SI derivatives were used in a wide concentration range (10−9–10−4 mol/L) for a pre-sowing treatment of winter wheat (Triticum aestivum L., two cultivars) and maize (Zea mays L., two hybrids) seeds in germinating experiments. All compounds were found to affect the growth of the axial organs of germinants, with the growth-stimulating or -inhibitory effect as well as its rate being considerably different for wheat and maize and, in many cases, also for roots and shoots. In addition, a pronounced concentration dependence of the effect was disclosed for many cases. The features of the molecular structure of SIs affecting their growth-regulating properties were elucidated. Compounds 4, 6, 7, and 8, which had exhibited a growth-promoting effect in germinating experiments, were used at appropriate concentrations for pot experiments on the same crops. For all compounds, the experiments showed a stimulating effect on the growth of roots (up to 80%), shoots (up to 112%), leaf area (up to 113%), fresh weights of roots (up to 83%), and aerial parts of the plants (up to 87%) or only on some of these parameters. The obtained results show a healthy outlook for the use of SI derivatives as promoting agents for improving the growth of cereal crop plants

Control of cucumber (Cucumis sativus L.) tolerance to chilling stress – evaluating the role of ascorbic acid and glutathione

Chilling temperatures (1-10 ºC) are known to disturb cellular physiology, cause oxidative stress via creating imbalance between generation and metabolism of reactive oxygen species (ROS) leading finally to cell and/or plant death. Owing to known significance of low molecular antioxidants - ascorbic acid (AsA) and glutathione (GSH) in plant stress-tolerance, this work analyzes the role of exogenously applied AsA and GSH in the alleviation of chilling stress (3°C)-impact in cucumber (Cucumis sativus L. cv. Vjaznikowskij 37) plants. Results revealed AsA and GSH concentration dependent metabolism of ROS such as superoxide (O2•‾) and the mitigation of ROS-effects such as lipid peroxidation (LPO) as well as membrane permeability (measured as electrolyte leakage) in C. sativus leaf discs. AsA concentration (750 µM) and GSH (100 µM) exhibited maximum reduction in O2•‾ generation, LPO intensity as well as electrolyte leakage, all of these were increased in cold water (3°C and 25°C)-treated leaf discs. However, AsA, in particular, had a pronounced antioxidative effect, more expressed in case of leaf discs during chilling (3°C); whereas, at temperature 25°C, some AsA concentrations (such as 50 and 100 mM AsA) exhibited a prooxidative effect that requires molecular-genetic studies. Overall, it is inferred that AsA and GSH have high potential for sustainably increasing chilling-resistance in plants