The assessment of cadmium nitrate effect on morphological and cytogenetic indices of spring barley (Hordeum vulgare) seedlings

Abstract

The influence of different concentrations of the heavy metal (Cd) − Cd(NO₃)₂ − on seedlings of four cultivars of the spring barley was studied (the length of shoots and roots, the percentage of germinated seeds and strong seedlings were estimated). The topic of this work is investigation of effects of cadmium nitrate doses range on seedlings of several cultivars of spring barley of different geographical origin and searching of the Cd critical dose. For realization of these goals, an analysis of visible changes of the plants morphology and cytogenetical analysis (for searching of the discovered morphological changes causes) are suitable. Cadmium enters plants organism by the root path, and with this, morphological and cytogenetic effects in the seedlings roots have the highest value. Suppression of growth processes was described with an increase in the dose of Cd, and the appearance of morphological anomalies of seedlings was noted. Thus, average shoots length was decreased twice on the Cd²⁺ concentrations range 0.15–0.4 mg mL⁻¹; at the range from 0.4 to 0.7 mg mL⁻¹, this index was maintained on the plateau, and at doses higher than 1 mg mL⁻¹, a total suppression of shoots development was noted. Cytogenetic analysis was performed to clarify the reasons for the formation of these reactions. The increase in the yield of cytogenetic disorders was revealed with increasing cadmium concentration, and the blockage of proliferation in the late stages of mitosis was marked. High frequencies of multipolar mitoses, anomalous dividing of chromosomes, chromosome agglutinations and pathological anaphases have been indicated. At maximum dose, the frequency of cells with cytogenetic anomalies was 19 times higher than at control variant. Doses of Cd, which can be considered as not so harmful for plants, were estimated as 0.1–0.2 mg mL⁻¹. 0.3–0.7 mg mL⁻¹ caused significant inhibition of growth processes, while doses higher than 1 mg mL^-1 can be considered as conditionally lethal ones. It is shown that the barley cultivars have a significant differentiation in their resistance to cadmium, and the probable causes of the formation of observed effects were considered on the basis of literature data. With this, the Cd dose of 0.35 mg mL⁻¹ can be considered as critical and can be used for searching of barley cultivars, which have the high tolerance to Cd influence. In perspective, such cultivars can be used for agricultural production in the territories with the high rates of Cd soil pollution.