S-methylmethionine (SMM) is an important intermediary compound in the sulphur metabolism and has been shown to play a possible role in moderating the damaging effects of low temperature stress. The present work investigated the extent to which SMM is capable of influencing the activity of antioxidant enzymes when the subtropical species maize is exposed to chilling temperatures during the early developmental phase. SMM was found to contribute to the protection of maize seedlings against low (<14°C) temperature stress by enhancing the activity of certain antioxidant enzymes to varying extents, and thus helping to neutralise the reactive oxygen species (ROS) formed at this temperature. Results obtained in a gradient plant growth chamber revealed that, with the exception of catalase, SMM increased the activity of all the antioxidants studied (glutathione reductase, glutathione-S-transferase, guaiacol peroxidase, ascorbate peroxidase), particularly in the lower ranges of the temperature gradient (6–14°C).
S-methylmethionine (SMM), a naturally occurring, biologically active compound, is a free amino acid derivative, which is increasingly recognised as playing an important part in the plant metabolism. SMM, which is synthesised from methionine, is involved in crucial processes in the S metabolism, such as the regulation of methionine and S-adenosyl methionine levels, the methylation processes taking place in cells, and the transport and storage of sulphur in certain phases of development. It is of great importance in the development of resistance to abiotic and biotic stress factors, as it is a direct precursor in the biosynthesis of the osmoprotectants and other S-containing compounds involved in defence mechanisms, while also influencing the biosynthesis of major plant hormones such as polyamines and ethylene. The present paper discusses our increasing understanding of the role played by SMM in the plant metabolism and its possible role in the improvement of traits that enable plants to overcome stress.
We prove that the tolerance lattice TolA of an algebra A from a congruence modular variety V is 0-1 modular and satisfies the general disjointness property. If V is congruence distributive, then the lattice Tol A is pseudocomplemented. If V admits a majority term, then Tol A is 0-modular.
Authors:E. Szabó-Bárdos, L. Wojnárovits, and A. Horváth
Formation of oxidizing and reducing radicals has been studied by pulse radiolysis of [Fe(CN)6]4––BrO
–CN– system in ethylene glycol — water solvent mixture. Oxidizing ·BrO2 and BrO radicals formed by electron scavenging with ·BrO
were identified and their reactions were investigated. The reaction of hydroxyl radicals with ethylene glycol leads to formation of reactive radicals with reducing properties and of compounds which reduce slowly in dark the ferricyanide formed in the reaction of ·BrO2 radical with ferrocyanide.
Entrepreneurship is widely accepted to be the engine of development. In the era of massive changes in the employment patterns and the emergence of self-employment, it is increasingly important to guide graduates towards self-employment. At the same time, the low intensity rates of youth in active citizenship behaviour require some intervention from higher education institutions. They are ideal settings for training and career guidance, especially if the curriculum contains elements of entrepreneurial orientation. The present article inquires into the motivation of graduates to choose the entrepreneurial path, with special emphasis on two variables, active citizenship and the concept of calling, which is novel in the career development literature.
Proprioception plays an essential role in motor control and in psychological functioning: it is the basis of body schema and the feeling of body ownership. There are individual differences in the processing accuracy of proprioceptive stimuli. Although proprioceptive acuity plays an important role in physical competence, there are contradictory findings concerning the role it plays in healthy psychological functioning. This study aims to shed more light on this association.
Material and methods
Sixty-eight young adults participated in this study. We estimated proprioceptive acuity by the reposition accuracy of elbow joint positions. We tested both dominant and non-dominant hands with two different versions of Joint Position Reproduction Test. Perceived physical competence, body awareness, and affectivity were assessed using questionnaires (Physical Competence scale of Body Consciousness Questionnaire, Somatic Absorption Scale, and Positive and Negative Affectivity Schedule, respectively).
No significant association between proprioceptive acuity and body awareness, perceived body competence, and positive and negative affect was found.
Proprioceptive acuity, measured in the elbow joint, does not play a substantial role in body awareness, perceived body competence, and affect.
Authors:J. Kristóf, R. Frost, J. Kloprogge, E. Horváth, and É. Makó
The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600°C. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433°C under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.
Authors:G. Szalai, M. Pál, E. Horváth, T. Janda, and E. Páldi
In the course of the Maize Consortium Project, investigations were made on the defence mechanisms employed by maize against various abiotic stress factors (low temperature, cadmium) and on the effects exerted by two compounds (S-methylmethionine, salicylic acid) capable of improving the stress resistance of plants to certain abiotic stresses. Salicylic acid (SA) was found to inhibit the uptake of cadmium (Cd), but caused damage to the roots, including a reduction in the activity of phytochelatin synthase (PCS), which meant that preliminary treatment with SA aggravated the damaging effect of Cd. It was also proved that as the result of 2-day treatment with Cd, there was a continuous rise in the Cd level in the plants, more Cd being accumulated in young leaves than in older ones. The PCS activity increased greatly after 24 hours, both in the leaves and in the roots, declining again after 2 days. The effect of SA was examined in both the hybrids and their parental lines, and the effect of this compound on the intensity of alternative respiration was also investigated. A comparison of chilling tolerance data and antioxidant enzyme activity indicated that these two parameters were not directly correlated to each other, i.e. antioxidant enzyme activity values could not be used to draw reliable conclusions on the chilling tolerance of maize lines and hybrids. With regard to the interaction between alternative respiration and salicylic acid, it was proved that exogenous hydrogen peroxide caused a similar increase in the ratio of alternative respiration to that observed after salicylic acid treatment. Abbreviations: SA, salicylic acid; Cd, cadmium; PCS, phytochelatin synthase; SMM, S-methylmethionine; PCs, phytochelatins; PAR, photosynthetically active radiation; TTC, triphenyl tetrazolium chloride; KCN, potassium cyanide; PSII, 2nd photochemical system; POD, guaiacol peroxidase; APX, ascorbate peroxidase; GR, glutathione reductase