Plasticity of Plantago lanceolata L. in Adaptation to Extreme Environmental Conditions.

This study aimed at characterizing some adaptive changes in Plantago lanceolata L. exposed to harsh conditions of a desert-like environment generating physiological stress of limited water availability and exposure to strong light. It was clearly shown that the plants were capable of adapting their root system and vascular tissues to enable efficient vegetative performance. Soil analyses, as well as nitrogen isotope discrimination data show that P. lanceolata leaves in a desert-like environment had better access to nitrogen (nitrite/nitrate) and were able to fix it efficiently, as compared to the plants growing in the surrounding forest. The arbuscular mycorrhiza was also shown to be well-developed, and this was accompanied by higher bacterial frequency in the root zone, which might further stimulate plant growth. A closer look at the nitrogen content and leaf veins with a higher number of vessels and a greater vessel diameter made it possible to define the changes developed by the plants populating sandy habitats as compared with the vegetation sites located in the nearby forest. A determination of the photosynthesis parameters indicates that the photochemical apparatus in P. lanceolata inhabiting the desert areas adapted slightly to the desert-like environment and the time of day, with some changes of the reaction center (RC) size (photosystem II, PSII), while the plants' photochemical activity was at a similar level. No differences between the two groups of plants were observed in the dissipation of light energy. The exposure of plants to harsh conditions of a desert-like environment increased the water use efficiency (WUE) value in parallel with possible stimulation of the ß-carboxylation pathway.

Congruence between the prioritisation of conservation problems at the local and national scale: an evaluation by environmental scientists in Poland.

The anthropogenic pressure on the environment depends on the spatial scale. It is crucial to prioritise conservation actions at different spatial scales to be cost-efficient. Using horizon scanning with the Delphi technique, we asked what the most important conservation problems are in Poland at local and national scales. Twenty-six participants, PhD students, individually identified conservation issues important at the local and national scales. Each problem was then scored and classified into broader categories during the round discussions. Text mining, cross-sectional analyses, and frequency tests were used to compare the context, importance scores, and frequency of identified problems between the two scales, respectively. A total of 115 problems were identified at the local scale and 122 at the national scale. Among them, 30 problems were identical for both scales. Importance scores were higher for national than local problems; however, this resulted from different sets of problems identified at the two scales. Problems linked to urbanisation, education, and management were associated with the local scale. Problems related to policy, forestry, and consumerism were more frequent at the national scale. An efficient conservation policy should be built hierarchically (e.g. introducing adaptive governance), implementing solutions at a national scale with the flexibility to adjust for local differences and to address the most pressing issues.

The Common Ice Plant (Mesembryanthemum crystallinum L.)-Phytoremediation Potential for Cadmium and Chromate-Contaminated Soils.

The common ice plant (Mesembryanthemum crystallinum L.) is a widely studied model due to its tolerance to numerous biotic and abiotic stresses. In this study, carried out in model pots, the plants were treated with variant doses of Cd(II) and Cr(VI) and proved resistant to extreme levels of these heavy metals. Initial toxicity symptoms were observed upon final concentrations of 818 mg Cd kg-1 soil d.w., and 1699 mg Cr kg-1 applied as potassium chromate. Biometric analyses revealed that none of the Cr(VI) doses affected dry weight of the plant organs thus maintaining the shoot-to-root ratio. The Cd and Cr hypertolerance strategies were divergent and resulted in different accumulation patterns. For the case of Cd(II), an excluder-like mechanism was developed to prevent the plant from toxicity. For chromate, high accumulation potential together with Cr(VI) root-to-shoot translocation at sublethal concentrations was revealed (up to 6152 mg Cr kg-1 shoot at 4248 mg Cr kg-1 soil). It is concluded that M. crystallinum reveals considerable phytoremediation capabilities due to unique growth potential in contaminated substrates and is suitable for bioreclamation of degraded soils. The plant is especially applicable for efficient phytoextraction of chromate-contamination, whereas for Cd-affected areas it may have a phytostabilizing effect.

Expression of Genes Involved in Heavy Metal Trafficking in Plants Exposed to Salinity Stress and Elevated Cd Concentrations.

Many areas intended for crop production suffer from the concomitant occurrence of heavy metal pollution and elevated salinity; therefore, halophytes seem to represent a promising perspective for the bioremediation of contaminated soils. In this study, the influence of Cd treatment (0.01-10.0 mM) and salinity stress (0.4 M NaCl) on the expression of genes involved in heavy metal uptake (irt2-iron-regulated protein 2, zip4-zinc-induced protein 4), vacuolar sequestration (abcc2-ATP-binding cassette 2, cax4-cation exchanger 2 pcs1-phytochelatin synthase 1) and translocation into aerial organs (hma4-heavy metal ATPase 4) were analyzed in a soil-grown semi-halophyte Mesembryanthemum crystallinum. The upregulation of irt2 expression induced by salinity was additionally enhanced by Cd treatment. Such changes were not observed for zip4. Stressor-induced alterations in abcc2, cax4, hma4 and pcs1 expression were most pronounced in the root tissue, and the expression of cax4, hma4 and pcs1 was upregulated in response to salinity and Cd. However, the cumulative effect of both stressors, similar to the one described for irt2, was observed only in the case of pcs1. The importance of salt stress in the irt2 expression regulation mechanism is proposed. To the best of our knowledge, this study is the first to report the combined effect of salinity and heavy metal stress on genes involved in heavy metal trafficking.

The response of a model C3/CAM intermediate semi-halophyte Mesembryanthemum crystallinum L. to elevated cadmium concentrations.

Many areas exhibiting increased concentrations of soluble salts are simultaneously polluted with heavy metals (HM), and halophytes with extended tolerance to heavy metal toxicity seem to represent a promising tool for their phytoremediation. In this study, the response of the soil-grown C3-CAM (Crassulacean acid metabolism) intermediate halophyte Mesembryanthemum crystallinum (common ice plant) to increased concentrations of Cd (0.01-1 mM) was investigated. None of the tested Cd treatments affected growth parameters or tissue water content of either C3 or CAM-performing plants. Chlorophyll a fluorescence confirmed high tolerance of the photosynthetic apparatus of both metabolic states towards Cd. Plants performing both photosynthesis types accumulated significant Cd amounts only under the highest (1 mM) treatment, and the metal was primarily deposited in the roots, which are features typical of an excluding strategy. Upon the application of 1 mM Cd solution CAM-performing plants, due to the NaCl pre-treatment applied for CAM induction, were exposed to significantly higher amounts of bioavailable Cd in comparison with those of C3-performing plants. As a result, roots of CAM plants accumulated over 4-fold higher Cd amounts when compared with C3 plants. In our opinion, enhanced Cd-accumulating potential observed in CAM-performing plants was the effect of osmotic stress episode and resulting modifications e.g. in the detoxifying capacity of the antioxidative system. Increased antioxidative potential of NaCl pre-treated plants was pronounced with significantly higher activity of CuZnSOD (copper-zinc superoxide dismutase), not achievable in C3 plants subjected to high Cd concentrations. Moreover, the applied Cd doses induced SOD activity in a compartment-dependent manner only in C3 plants. We confirmed that none of the applied Cd concentrations initiated the metabolic shift from C3 to CAM.