Natalia Kaznina

Effect of lead on the photosynthetic apparatus of annual grasses

The effect of lead (in the form of Pb(CH3COO)2 ⋅ 3H2O at concentrations of 200, 400, and 800 mg/kg substrate) on the photosynthetic apparatus of barley (cv. Dina) and oat (cv. Falensky) 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.

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 substrate had no significant effect on most of the plant growth parameters. However, higher metal concentrations (160 and 320 mg kg substrate) inhibited shoot biomass, leaf area, inflorescence length, and biomass. At the same time, parameters such as the content of chlorophyll (a + b), F 0, Fv, and the Fv/Fm rate were not reduced even in the presence of zinc in the highest concentrations (320 mg kg 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 stage. 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.

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, remained at the level of those in control plants. A high resistance of green foxtail to the effects of cadmium was established, which is provided with different adaptive mechanisms and anatomical and physiological characteristics associated with its affiliation to the group of C4-plants.

The content of HvHMA2 and HvHMA3 transcripts in barley plants treated with cadmium

The content of transcripts of HvHMA2 and HvHMA3 genes in roots and leaves of 3-day-old (the stage of seed germination) and 7-day-old (the seedling stage) barley (Hordeum vulgare L., cv. Zazerskii 85) seedlings in the presence of cadmium ions (100 μM) was studied. Some organ-specific and age-related differences in the level of mRNAs of studied genes were identified. So, after a 4-day exposure of plants to a solution containing cadmium ions, the level of transcripts of HvHMA3 gene increased in the roots of 3-day-old seedlings, contributing to the sequestration of toxic ions in the vacuole. The level of HvHMA2 transcripts increased stronger in 7-day-old seedlings, especially in the leaves, which apparently may lead to an increased inflow of the metal ions in the phloem and to an activation of its translocation from the leaves to the roots. The observed decrease in this gene transcripts in the roots contributed in its turn to a limitation of cadmium transport to the shoots. A conclusion about the possible involvement of HvHMA2 gene in an increase of resistance of 7-day-old barley plants to cadmium was drawn based on the comparison of gene transcripts and the resistance of seedlings of different ages to this metal.

Оценка степени техногенного загрязнения окружающей среды тяжелыми металлами по состоянию растительности

The study of herbaceous vegetation growing in different parts of the City of Petrozavodsk varying in lead-pollution levels was conducted. It was established that the herbaceous communities formed at contaminated sites were characterized by fewer species (genera and families) than those in the relatively clean territories, a higher share of more tolerant species of the family Poaceae , and a decrease in the production of aboveground biomass. At the same time, a decrease in the absolute values of a majority of morphometric characters, among which the most sensitive to soil pollution is “leaf surface area” of the second leaf from the inflorescence, is observed in the dominant grass species ( Dactylis glomerata L. and Phleum pratense L.). The conclusion on the applicability of a number of parameters characterizing the state of vegetation as a whole and individual plant species as criteria for assessing the level of environmental pollution with heavy metals (in particular lead) which, in turn, can be used for early diagnosis of diseases in the population inhabiting the territories, is drawn.