Effect of Seed Treatment with Salicylic Acid on the Carbonic Anhydrase Activity, Photosynthesis Rate, Stomatal Conductance, and Pigments Content in Wheat Leaves at Zinc Excess.

The effect of seed treatment with salicylic acid (SA) on the carbonic anhydrase (CA) activity, photosynthesis rate, stomatal conductance, and pigment content in wheat leaves was studied at an optimal zinc content (2 µM) and zinc excess (1500 µM). It was shown for the first time that the CA activity and stomatal conductance increased upon seed treatment with SA at the optimal zinc content as compared with untreated plants, while the photosynthesis rate was not affected. When zinc was in excess in the root zone, seed treatment with SA decreased the CA activity to a greater extent, but the photosynthesis rate was higher than in untreated plants, apparently due to an increase in the contents of chlorophylls and carotenoids and stomatal conductivity. It was concluded that SA is involved in the protective and adaptive responses of wheat plants to excess environmental zinc along with other nonhormonal factors and hormones.

Effect of Methyl Jasmonate on the Gene Expression, Encoding Non-Protein Thiol Enzymes in Wheat under Cadmium.

The effect of the phytohormone methyl jasmonate (MJ) on the expression of the TaGS1 and TaPCS1 genes encoding glutathione synthetase and phytochelatin synthase, respectively, which are key enzymes in the synthesis of glutathione and phytochelatins in wheat (cv. Moskovskaya 39), was studied. It was shown for the first time that pretreatment of plants by exogenous MJ (1 µM) leads to an increase in the accumulation of transcripts of the TaGS1 and TaPCS1 genes in leaves without cadmium effect. When cadmium (CdSO4, 100 µM) was added into the nutrient solution, the transcript level of the TaGS1 gene in the plants pretreated by MJ increased (compared to the untreated plants), whereas the transcript level of TaPCS1 remained unaffected. The pretreatment of plants with MJ leads to a lower accumulation of cadmium in the roots and leaves of wheat. At the same time, MJ had no effect on the linear growth parameters of plants, but had a positive effect on the accumulation of biomass under cadmium. It was assumed that MJ is involved in plant tolerance to cadmium by increasing the expression of the TaGS1 and TaPCS1 genes and, as a result, enhancing the synthesis of chelating compounds, as well as by reducing the supply of metal ions to plants.

Seed Treatment with Salicylic Acid Increases Gene Expression and Activity of Antioxidant Enzymes in Wheat Plants in Zinc or Copper Deficiency.

The effect of wheat seed treatment with salicylic acid (SA) on expression of the TaCu/ZnSOD, TaFeSOD, and TaCAT2 genes and activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in leaves was studied at optimal contents of zinc (2 µM) and copper (0.3 µM) in the root environment and in zinc and copper deficiencies. Seed treatment with SA was for the first time shown to increase of the amount of transcripts of the above genes as compared with untreated plants, both in optimal conditions and in zinc or copper deficiency. Activities of the enzymes, especially catalase, also increased. Judging by the malondialdehyde (MDA) content, the changes make it possible to avoid an increase in lipid peroxidation (LPO) and, therefore, oxidative stress. A positive effect of seed treatment with SA on activities of the main antioxidant enzymes was assumed to underlie the stimulating effect of SA on physiological processes in plants exposed to microelement deficiency.

The HMA2 Gene Expression in Leaves of Introgressive Wheat Lines under Zn Optimum and Deficiency Content in Root Environment.

In two introgressive lines of bread wheat (15-7-1 and 15-7-2), which differ in the allelic status of the Gpc-B1 gene, the expression of the gene encoding the HMA2 transport protein in flag leaves under optimum Zn content in substrate (2 µÐœ) and in its deficiency (0 µÐœ) was investigated. This is the first study to show that the plants carrying functional allele of the Gpc-В1 gene (line 15-7-1) have a higher level of TaHMA2 transcripts than the plants with nonfunctional allele of the Gpc-В1 gene (line 15-7-2) both at optimum Zn content in substrate and at its deficiency. Importantly, the high TaHMA2 gene expression did not affect the wheat shoot growth but correlated with a high Zn concentration in the aboveground part of plants. It is assumed that the NAC transcription factor encoded by the Gpc-В1 gene may be involved in the regulation of the ТаНМА2 gene expression.

Effect of Zinc Excess and Low Temperature on the IRT1 Gene Expression in the Roots and Leaves of Barley.

We studied the effect of zinc excess (1000 µM) and low positive temperature (4°C) on the IRT1 gene expression in barley roots and leaves. Exposure at each of the stress factors separately induced an increase in the content of the HvIRT1 gene transcripts, which was more pronounced in leaves. At the same time, the growth of seedlings continued. Under the combined action of the stress factors in the first 3 days, the amount of mRNA also increased, but after 7 days of exposure it significantly declined, which correlated with the complete inhibition of seedling growth. It is assumed that the seedling growth inhibition under the combined effect of zinc excess and low temperature is associated with a decrease in the transcriptional activity of the HvIRT1 gene, due to the deficiency in a number of trace elements under these conditions.

[The resistance of plants Setaria veridis (L.) Beauv. to the influence of cadmium].

It was shown that cadmium causes a slowdown of green foxtail Setaria veridis (L.) Beauv. shoots; however it had no effect on root growth or accumulation of underground and above-ground biomass. In the analysis of the effect of cadmium on the water regime and photosynthesis of plants, it was found that it had a negative effect on the stomatal-apparatus, which led to a decrease in the transpiration rate and stomatal conductance. It was noted that the water content of tissues, as well as the rate of photosynthesis in the presence of cadmium, reinained at the level of those in'control planrits. A high resistance of green foxtail to the effects of cadmium was established, which is provided with different adaptive mechanisms and anatomical and physiologicdal characteristics associated with its affiliation to the group of C4-plants.

[Setaria viridis tolerance of high zinc concentrations].

The effect of high zinc concentrations on the growth and photosynthetic apparatus of Setaria viridis (L.) Beauv. was investigated under laboratory conditions and a vegetation experiment. The experiments showed that zinc concentrations of 10(-6) to 10(-3) M did not influence seed germination. Moreover, zinc in concentrations of 40 and 80 mg kg(-1) substrate had no significant effect on most of the plant growth parameters. However, higher metal concentrations (160 and 320 mg kg(-1) substrate) inhibited shoot biomass, leaf area, inflorescence length, and biomass. At the same time, parameters such as the content of chlorophyll (a + b), F0, F(v), and the F(v)/F(m) rate were not reduced even in the presence of zinc in the highest concentrations (320 mg kg(-1) substrate). S. viridis tolerance of high zinc concentrations, as well as its capacity to accumulate zinc in roots and shoots, suggests the plant can be used for phytoremediation of zinc polluted soils.

[The effect of cadmium on shoot apical meristems of barley].

We studied the effects of cadmium acetate at various concentrations (200 to 800 mg/kg substrate) on growth and development of shoot apical meristem of the barley plants (Hordeum vulgare L.) under the conditions of vegetative experiment. It was shown that in the presence of increasing cadmium concentrations in the soil substrate, the apex length and number of inflorescence elements decreased and the rate of organogenesis slowed down, thus affecting the spike potential productivity and morphological parameters of barley plants at the flowering phase. It is possible that the negative effect of cadmium on the shoot apical meristem is associated with its influence on division of the apex cells.

[Effect of lead on the photosynthetic apparatus of annual grasses].

The effect of lead (in the form of Pb(CH3COO)2 x 3H2O at concentrations of 200, 400, and 800 mg/kg substrate) on the photosynthetic apparatus of barley (cultivar Dina) and oat (cultivar Falenskii) was studied. Exposure to low concentrations of lead (200 mg/kg) slightly increased the content of chlorophyll in leaves and the rate of photosynthesis. Medium concentrations of lead (400 mg/kg) had no marked effect on the parameters analyzed, whereas high concentrations (800 mg/kg) decreased the area of leaves, the content of green pigments in them, and the rate of photosynthesis.