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

Acetolactate synthase activity and foliar absorption in the presence of chlorsulfuron in biotypes of Cirsium arvense (L.) Scop.

The mechanism of acetolactate synthase (ALS) resistance to the inhibitory action of sulfonylurea is due to the selection of R1 and R2 biotypes of C. arvense with modified form of the ALS enzyme. They are less susceptible to the inhibition of sulfonylurea, but still functional. There was no significant difference between the susceptible and sulfonylurea-resistant biotypes in absorption and translocation of chlorsulfuron

Cadmium-induced changes in the membrane lipid composition of maize plants

The effect of 10, 25 and 50 μM Cd(NO 3 ) 2 on the fatty acid composition was investigated in young maize seedlings ( Zea mays L., hybrid Norma). After 7 days’ exposure to cadmium slight changes were observed in the fatty acid composition, which were more pronounced in the roots than in the leaves. In the leaves cadmium did not affect the lipid composition of the monogalactosyldiacylglycerol (MGDG) or digalactosyldiacylglycerol (DGDG) fractions, while in the phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) fractions there was a decrease in the proportion of hexadecanoic acid (16:0) and an increase in the level of linoleic acid (18:2) and linolenic acid (18:3). The proportion of trans -Δ3-hexadecanoic acid in leaf PG also decreased. In the roots significant changes were observed in all the fractions examined after Cd stress. In the MGDG the level of stearic acid (18:0) and oleic acid (18:1) decreased, but that of 18:2 and 18:3 increased. In the case of PE the amount of 16:0 decreased, while that of 18:0, 18:1 and 18:3 increased. In the PG fraction the proportion of 16:0, 18:0 and 18:1 decreased, while that of 18:2 increased. The ratio of 16:0 also decreased in the DGDG fraction, while that of 18:0, 18:1 and 18:2 increased. The changes in the fatty acid composition were associated with an increase in the double-bond index and in the percentage of unsaturation in leaf PG, and in the MGDG, PG and DGDG fractions in the roots

Detection of genome-specific ribosomal DNA sequences from bread wheat by a modified PCR-based method

Although the nuclear ribosomal ITS region is the marker most frequently used for the molecular analysis of plant origin, little use has been made of this region to determine the origin of common wheat. The present work demonstrates that the nrITS region is suitable for research on the origin or evolution of wheat, not via direct PCR and sequencing, but by means of a novel PCR technique. This PCR analysis involved a combination of high denaturing temperature and high-fidelity Pfu polymerase, followed by product cloning and the sequencing. In this way sequences were revealed that remained undetected using the conventional technique and that bore traces of earlier hybridisations, allowing conclusions to be drawn on the original ITS sequences of the units involved in the hybridisation. It was demonstrated that the direct nrITS sequence of common wheat may be hybrid in nature, and that the results obtained by means of direct sequencing must be treated with caution in wheat and other allopolyploid organisms. With the help of the method described here, it should be possible to avoid such errors

Role of Reactive Oxygen Species in Abiotic and Biotic Stresses in Plants

Biotic and abiotic stresses induce increased formation of reactive oxygen species (ROS) through distinct pathways: pathogen infections activate specific ROS-producing enzymes (i.e. NADPH oxidase, cell wall peroxidases), which results in accumulation of cellular or intercellular ROS, such as superoxide or hydrogen peroxide. Abiotic stresses, on the other hand, cause elevated ROS production principally through an impairment of photosynthetic and respiratory electron transport pathways. Also, these two types of stresses have diverse effects on the antioxidant system of the plant. Results of experiments studying the interaction of abiotic and biotic stresses largely depend on the degree of the applied abiotic stress treatment, the compatible or incompatible host-pathogen interaction and the timing of inoculation in relation to the timing of a preceding abiotic stress treatment

Protective effect of the naturally occurring, biologically active compound S-methylmethionine in maize seedlings exposed to a short period of cold

The work was aimed at investigating short-term metabolic changes caused by S-methylmethionine (SMM) and at clarifying the gene expression background of these changes in order to gain a better understanding of the protective effect of SMM against stress. When examining the expression of genes coding for the enzymes responsible for the biosynthesis of polyamines, which play an important role in responses to low temperature stress, and that of the C-repeat binding transcription factor (CBF1) gene, it was found that both SMM and cold treatment increased the expression of genes responsible for the polyamine synthesis pathway starting from arginine. It caused only a slight increase when applied alone, but when SMM pre-treatment was followed by cold stress, it resulted in a considerable extent of up-regulation. SMM caused a similar increase in the expression of CBF1. The changes in the expression of genes responsible for the polyamine synthesis were clearly reflected in changes in the putrescine and agmatine contents, while the greater increase in the spermidine content was indicative of the role of SMM as a direct precursor in spermidine biosynthesis. The results demonstrated that, in addition to its direct effect on the sulphur metabolism and on polyamine biosynthesis, the protective effect of exogenous SMM was chiefly manifested in its influence on the expression of genes responsible for the biosynthesis of the polyamines important for stress responses and on the CBF1 transcription factor gene that acts as a regulator in cold stress