Małgorzata Wierzbicka

The effect of lead on seed imbibition and germination in different plant species

Abstract A study was conducted to determine the extent to which seed coats are a barrier to lead and to what degree germination is affected by this heavy metal. The study was carried out on 25 species of plants from 12 families, represented by different varieties and populations. In all, 34 types of seeds were tested. Comparative observations were conducted on the effect of barium nitrate on seed imbibition and germination. Seeds were treated with solutions of the following salts during imbibition: 100, 1000, and 10 000 mg dm−3 Pb2+ from Pb(NO3)2 and 1000 mg dm−3 Ba2+ from Ba(NO3)2. The histochemical rhodizonate method was used to determine the distribution of lead and barium in the seeds. Water uptake and germination dynamics were also studied. It was found that 28% of the studied plant species had seed coats that were permeable to lead ions, 39% were permeable to barium ions. In both cases these species belonged to three families: Papilionaceae, Crucifereae and Graminae. Lead delayed germination and lowered the ability of seeds to germinate in a dose-dependent manner in the species with highly lead-permeable seed coats. In some other species, germination was delayed only a few hours. In all, a significant effect of lead on germination was found in over half of the studied species. It was shown that lead did not act by inhibiting water uptake during imbibition. It was also shown that seed coat permeability varied during imbibition of seeds with coats highly permeable to lead. Seed coats were impermeable to lead in the first period of imbibition when water uptake is intense. In the final stages of imbibition, when water uptake is reduced, seed coats became more permeable to lead. The lead that penetrated into the embryos in the final stage of imbibition delayed germination. This shows that seed coats are selectively permeable to lead ions.

Lead accumulation and its translocation barriers in roots of Allium cepa L.-autoradiographic and ultrastructural studies

Lead migrating through the tissues of Allium cepa L. was found, by electron microscopy, autoradiography and other methods, to encounter at least three barriers to penetration. The layers of protoderm and hypodermic meristematic cells in the root meristematic zone and the layer of endodermis in the mature root zone were barriers to apoplastic transport. The central zone was a barrier to apoplastic and symplastic transport. It comprises the quiescent centre in the root meristem and the central part of the root cap. The cells of the deepest ground meristematic tissue layers seemed to act as a barrier, which keeps lead away from the procambium. Lead accumulated in roots but it was not uniformly distributed between their various tissues. The largest amount of lead accumulated both in ground meristematic and cortex tissues.

Comparison of lead tolerance in Allium cepa with other plant species

Abstract Our previous studies demonstrated increased lead tolerance of Allium cepa adventitious root tip cells during treatment with lead. We then compared the degree of tolerance to lead of A. cepa and 22 groups of plants (species, varieties, populations). We showed that initially, constitutional tolerance of A. cepa to lead was moderate, then high, similar to inducible tolerance of calamine waste heap plants. It is noteworthy that this high tolerance was characteristic for only A. cepa plants developing from bulbs. Plants developing from seeds demonstrated a lower tolerance to lead (by 7 to 45%). The high constitutional tolerance of A. cepa growing from bulbs was related to the possibility of transporting large amounts of lead (40%) from the roots to the bulb. These results point to the role played by the storage organ (bulb) in raising the tolerance of A. cepa to lead, which is demonstrated for the first time in this study, and which is interpreted as an element of constitutional tolerance to lead. It was found that the constitutional tolerance of crop plants ranged from 78 to 2%, depending on the species, variety, development stage, and duration of treatment with lead. The inducible tolerance of plants from the waste heap ranged from 130 to 10%. In these plants, the increased tolerance resulting from the adaptation to growing on a polluted waste heap averaged 18.5%. The following order of decreasing tolerance to lead was found: I. Species with the highest tolerance, i.e. with inducible tolerance, from the waste heap: Silene vulgaris > Biscutella laevigata > Leontodon hispidus . II. Species with high constitutional tolerance: B. laevigata natural population> A. cepa growing from bulbs> Hordeum vulgare > Zea mays . III. Species with intermediate, most common, constitutional tolerance: A. cepa growing from seeds> Triticum vulgare > Pisum sativum > Cucumis sativus > Lupinus luteus > Raphanus sativus > Secale cereale . IV. Species with low constitutional tolerance: Brassica napus > Soja hispida > Phaseolus vulgaris . The species, varieties and populations differed considerably among each other in terms of lead uptake. Although no relationship was found between the degree of tolerance to lead and the amount of lead in a plants tissues, the pattern of lead distribution was similar in almost all of the plants.

The adaptation of Silene vulgaris to growth on a calamine waste heap (S. Poland)

Abstract Two populations of Silene vulgaris (Moench) Garcke (= S. inflata Mill.= S. cucubalus (L.) Wib.) were cultivated and compared. One population was from a calamine waste heap in Boleslaw near Olkusz in southern Poland, the other a normal population from the Botanical Gardens in Warsaw. In comparison with the normal population, the plants from the waste heap population were characterized by faster growth, thicker and narrower leaves, and trailing shoots of small diameters. The xeromorphic adaptations of the waste heap population were accompanied by increased water stress resistance (PEG 6000 test). The main life strategy (type r) of the calamine waste heap population, associated with growth under the difficult conditions of the place, is based on accelerated growth and rapid entry into the generative phase. The smaller biomass gain of these plants is compensated for by abundant flowering (by 23%). Moreover, these plants exhibit a very high tolerance to lead. Tests with PbCl 2 showed that lead stimulated root elongation (up to 164% of controls), biomass gain of roots, and formation of root hairs.

Mitotic Disturbances Induced by Low Doses of Inorganic Lead

SUMMARYAdventitious roots of Allium cepa L. have been treated with the sublethal dose of 2.5 mg dm−3 Pb2+ as well as the partly lethal one—3.0 mg dm−3 Pb2+ derived from two lead compounds: PbCl2 and Pb(NO3)2. These compounds induced numerous C-mitoses. This effect coincided with a strong inhibition of the root growth and lowering of the mitotic activity. However, lead effect in this range does not constitute a genetic threat in natural environment, since lead doses with such strong effects do not normally occur in the environment. However the lower lead dose, 1.0 dm−3 Pb2+ from PbCl2 and Pb(NO3)2 resulted in slight but statistically significant clastogenic effects, without disturbing the mitotic activity. It has further been found that lead chloride (the component of car exhaust gas) administered in the low dose (1 mg dm−3) was more clastogenic than lead nitrate. The presented results point to a potentially mutagenic effect of low lead doses.

The adaptation of Dianthus carthusianorum L. (Caryophyllaceae) to growth on a zinc–lead heap in southern Poland

Plants of Dianthus carthusianorum from a calamine (zinc–lead) waste heap and from unpolluted stands were compared in the field and under controlled laboratory conditions. It was found that the waste-heap plants differed significantly from those in the normal population in respect to the following morphological traits: lower weight of aerial parts, shorter and narrower leaves, smaller number of leaves per plant. In combination with shorter, less numerous shoots, these features reduce the transpiration area of the plants. The general habit (predominance of forms with short and trailing shoots) of the waste-heap population points to adaptation to a xeric environment. Under controlled conditions all of the above traits were maintained through three successive generations. They are thus genetically controlled. Root tolerance tests showed that the waste-heap plants had higher tolerance to zinc and lead. These results indicate that strong selection processes have generated a clear ecotypical differentiation for heavy metal tolerance and drought tolerance in a zinc–lead-rich waste-heap population of D. carthusianorum (variety).

Differences in lead tolerance between Allium cepa plants developing from seeds and bulbs

Tolerance to lead of three of Allium cepa L. varieties grown from seeds and bulbs was compared. In all cases plants developing from bulbs were found more tolerant to lead than those developing from seeds. During 10 days of exposure to lead, the difference in the tolerance index between adventitious and seedling roots was 24% on average (7-61% depending on the plant variety and the dose of lead), which was significant. In all cases, the seedlings contained more lead in their tissues than the plants that had developed from bulbs. This observation may explain a difference in lead tolerance between these developmental phases of Allium cepa.

Biological and chemical investigation of Allium cepa L. response to selenium inorganic compounds

AbstractThe aim of this study was to evaluate the biological and chemical response of Allium cepa L. exposed to inorganic selenium compounds. Besides the investigation of the total content of selenium as well as its chemical speciation, the Allium test was used to evaluate the growth of onion roots and mitotic activity in the roots’ meristem. The total content of selenium was determined by inductively coupled plasma mass spectrometry (ICP MS). High-performance liquid chromatography (HPLC), coupled to ICP MS, was used for the selenium chemical speciation. Results indicated that A. cepa plants are able to biotransform inorganic selenium compounds into their organic derivatives, e.g., Se-methylselenocysteine from the Se(IV) inorganic precursor. Although the differences in the biotransformation of selenium are due mainly to the oxidation state of selenium, the experiment has also shown a fine effect of counter ions (H+, Na+, NH4+) on the response of plants and on the specific metabolism of selenium. Figureᅟ

Multidimensional evaluation of soil pollution from railway tracks

Railway transport is a source of pollution to soils and living organisms by e.g. PAHs, PCBs, oil-derived products, pesticides and heavy metals. Soil toxicity evaluation requires chemical analyses, indicating the type and content of particular pollutants, as well as biological analyses, which allow assessing the reaction of organisms to these pollutants. This paper is focused on a multi-aspect evaluation of the degree of toxicity and pollution of soil in selected railway areas from north-eastern Poland by application of numerous biotests and chemical analyses. The soils were sampled on railway tracks from the following railway stations: Białystok Fabryczny, Siemianówka, Hajnówka, Iława Główna and Waliły. The most toxic soils occur on the railway tracks at Białystok Fabryczny and Siemianówka. They had a significant toxic effect on test organisms from various trophic levels. The contents of PAHs, PCBs, heavy metals, oil-derived hydrocarbons and pesticide residues were determined in the examined soils. In all cases the detected pollutants did not exceed the admissible levels. The highest content of oil-derived substances was noted in soils from Białystok Fabryczny and concentrations were moderate in soils from Siemianówka. Although the pollutants determined in soils from railway tracks did not exceed the admissible values, they had a toxic effect on numerous test organisms from different trophic levels. This suggests a synergistic effect of low concentrations (within the admissible levels) of several pollutants together, which resulted in a toxic effect on the organisms. Thus, there is a strong need of not only chemical, but also ecotoxicological analyses during the evaluation of environmental conditions. Based on data obtained from biological and chemical analyses, we concluded that railway transport may pose a hazard to the natural environment to a larger extent that hitherto expected.

Antimitotic effect of Selol and sodium selenate (IV) on Allium test cells

Selol is a mixture of selenitetriglycerides, obtained by esterification of pre-oxidated triglycerides from sunflower oil with selenous acid. Investigations have been carried out on the anticancer use of Selol and its antimitotic properties. The aim of our work was to compare the effect of two compounds (an organic and an inorganic one) containing selenium with oxidation number at +4: Selol and sodium selenate (IV), on plant cells of Allium test. Structural changes in cells, their mitotic activity and proportions of mitotic phases were subject to experimental analysis. Incubation in both selenium compounds led to changes in structure of chromosomes, consisting in their strong condensation and contraction (cc chromosomes), accompanied by gradual reduction or complete inhibition of cell division. High concentrations of Selol led to strong condensation of chromatin in interphase cells, while cells treated with high concentrations of sodium selenate (IV) displayed typical “pseudoapoptotic” bodies and totally fragmented nuclei. Both compounds caused inhibition of cell division; however, sodium selenate (IV) was more effective, while low concentrations of Selol stimulated division. Use of Selol resulted in changes in chromosome structure, condensation and contraction, which made it impossible to pass to further phases of cell division. The effect of sodium selenate (IV) consisted in raised prophase index, and high concentrations led to inhibition of divisions and arrest of cells at different stages of mitosis. The results obtained show markedly lower toxicity of Selol in comparison with sodium selenate, which makes it advisable to further investigate that compound as a potential safe anticancer drug.