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Drought Differently Modifies Tolerance and Metal Uptake in Zn- or Cu-Treated Male and Female Salix × fragilis L.
The aim of this study was to determine the tolerance to metals (Zn, Cu) and drought of male and female Salix × fragilis L. under isolated and combined treatments, and to assess the metal uptake and profiling of metabolic plant responses. The 14-day experiment was performed in a hydroponic system, and metals were applied at 1.5 mM in a Knop’s solution. Drought simulation was achieved by adding sorbitol at a moderate level (200 mM). Isolated Zn treatment enhanced plant growth, more pronouncedly in females. Equimolar Cu treatment caused diverse reactions, and females exhibited significantly higher tolerance. Male specimens were less tolerant to isolated drought and to combined drought and metal presence. The highest contents of Cu and Zn were found in roots, compared to the aboveground tissues (wooden rods and leaves), of both female and male metal-treated plants. Simultaneously applied drought limited Zn accumulation in roots and elevated its translocation to leaves while increasing Cu accumulation, predominantly in females showing higher tolerance. Both isolated and combined drought and metals reduced leaf water content, caused the allocation of mineral nutrients (Ca, Mg, K, and Na), and affected metabolism in a stressor-specific and sex-dependent manner. For males, Cu accumulation in the leaves was significantly correlated with the majority of metabolites, while for both sexes, kaempferol and salicylic acid were strongly correlated, indicating their role in tolerance against the metal. The obtained results are an excellent starting point for the practical use of male and female Salix × fragilis L. in areas heavily polluted with Cu or Zn and exposed to drought, for the purpose of their recultivation.
Seasonality Affects Low-Molecular-Weight Organic Acids and Phenolic Compounds’ Composition in Scots Pine Litterfall
Background and Aims: Secondary plant metabolites, including organic acids and phenolic compounds, have a significant impact on the properties of organic matter in soil, influencing its structure and function. How the production of these compounds in foliage that falls to the forest floor as litterfall varies across tree age and seasonality are of considerable interest for advancing our understanding of organic matter dynamics. Methods: Monthly, we collected fallen needles of Scots pine (Pinus sylvestris L.) across stands of five different age classes (20, 40, 60, 80, and 100 years) for one year and measured the organic acids and phenolic compounds. Results: Seven low-molecular-weight organic acids and thirteen phenolic compounds were detected in the litterfall. No differences were observed across stand age. Significant seasonal differences were detected. Most compounds peaked during litterfall in the growing season. Succinic acid was the most prevalent organic acid in the litterfall, comprising 78% of total organic acids (351.27 ± 34.27 µg g− 1), and was 1.5 to 11.0 times greater in the summer than all other seasons. Sinapic acid was the most prevalent phenolic compound in the litterfall (42.15 µg g− 1), representing 11% of the total phenolic compounds, and was 39.8 times greater in spring and summer compared to autumn and winter. Growing season peaks in needle concentrations were observed for all thirteen phenolic compounds and two organic acids (lactic, succinic). Citric acid exhibited a definitive peak in late winter into early spring. Conclusions: Our results highlight the seasonal dynamics of the composition of secondary plant metabolites in litterfall, which is most different at the onset of the growing season. Fresh inputs of litterfall at this time of emerging biological activity likely have seasonal impacts on soil’s organic matter composition as well.
Copper, lead and zinc interactions during phytoextraction using Acer platanoides L. - a pot trial
AbstractOf the many environmental factors that modulate the phytoextraction of elements, little has been learnt about the role of metal interactions. The study aimed to show how different concentrations of Cu, Pb and Zn in the cultivation medium influenced the biomass, plant development and phytoextraction abilities ofAcer platanoidesL. seedlings. Additionally, the impact on the content and distribution of Ca, K, Mg and Na in plant parts was studied with an analysis of phenols. Plants treated with a mixture of two metals were characterised by lower biomass of leaves and higher major elements content jointly than those grown in the salt of one element. Leaves ofA. platanoidescultivated in Pb5 + Zn1, Pb1 + Zn1and Pb1 + Zn5experimental systems were characterised by specific browning of their edges. The obtained results suggest higher toxicity to leaves of Pb and Zn present simultaneously in Knop solution than Cu and Pb or Cu and Zn, irrespective of the mutual ratio of the concentrations of these elements. Antagonism of Cu and Zn concerning Pb was clearly shown in whole plant biomass when one of these elements was in higher concentration (5 mmol L−1) in solution. In the lowest concentrations (1 mmol L−1), there was a synergism between Cu and Zn in plant roots. Plants exposed to Zn5, Cu1 + Pb5, Pb5 + Zn1and Cu1 + Zn1were characterised by higher total phenolic content than the rest plants. Both the presence and the concentration of other elements in the soil are significant factors that modulate element uptake, total phenolic content, and plant development.Graphical Abstract
The Influence of Water Conditions on Heavy Metal Tolerance Mechanisms in Hybrid Poplar (Populus nigra × Populus maximowiczii) in the Light of Sustainable Development Goals
Sustainable management of soils degraded by heavy metals is a major environmental challenge. The aim of this study was to evaluate the acclimatization ability of the hybrid Populus nigra L. × Populus maximowiczii under variable soil moisture conditions. In a greenhouse experiment, it was shown that both soil moisture level and the presence of metals significantly affected plant growth and metabolism. The hybrid showed high nickel (Ni) accumulation at low and medium soil moisture content (LMC, MMC) (BCF 4.56 and 4.99), while copper (Cu) accumulation was highest at MMC (BCF 5.53). Nickel translocation to aerial parts increased after exposure (TF up to 0.63), while Cu translocation was limited (TF below 0.94). Increased humidity promoted the biosynthesis of low molecular weight organic acids (LMWOAs) in roots, with the highest total content recorded in the Cu treatment under high soil moisture content (HMC) (230 μg g−1 FW). In the stems, the highest levels of sum LMWOAs were found under HMC conditions (6764 μg g−1 FW in the control sample), while among the phenolic acids, the highest content of chlorogenic acid (~144 μg g−1 FW) was determined under LMC conditions under Ni stress, which indicates a strong defense response of the plant. The obtained results emphasize the importance of selecting appropriate water conditions in remediation strategies and indicate that the tested poplar hybrid may be a promising tool in improving the quality of degraded soils.
Wpływ deficytu wody na zdolności fitoremediacyjne oraz poziomy stresu oksydacyjnego topoli energetycznej (Populus Maximowiczii x nigra) w świetle postępujących zmian klimatycznych
Early Response of the Populus nigra L. × P. maximowiczii Hybrid to Soil Enrichment with Metals
This study aimed to investigate the response of Populus nigra L. × Populus maximowiczii to the addition of selected metals in soil. Rooted cuttings were planted in pots containing soil enriched with equimolar concentrations of Pb, Zn, Al, Ni, and Cu (500 mL of 4 mM solutions of single metal salts: (Pb(NO3)2; Zn(NO3)2 × 6H2O; Al(NO3)3 × 9H2O; Ni(NO3)2 × 6H2O; or Cu(NO3)2 × 3H2O). Growth parameters, metal accumulation, and physiological and biochemical parameters were assessed after four weeks of cultivation, simulating early response conditions. The results showed diverse metal accumulation in poplar organs, along with an increase in biomass and minor changes in gas exchange parameters or chlorophyll fluorescence. Among low-molecular-weight organic acids, citric and succinic acids were dominant in the rhizosphere, and roots with malonic acid were also present in the shoots. Only p-coumaric acid was found in the phenolic profile of the roots. The shoots contained both phenolic acids and flavonoids, and their profile was diversely modified by particular metals. Sucrose and fructose content increased in shoots that underwent metal treatments, with glucose increasing only in Cu and Al treatments. Principal component analysis (PCA) revealed variations induced by metal treatments across all parameters. Responses to Pb and Zn were partially similar, while Cu, Ni, or Al triggered distinct reactions. The results indicate the adaptation of P. nigra L. × P. maximowiczii to soil containing elevated levels of metals, along with potential for soil remediation and metal removal. However, further studies are needed to evaluate the effect of differences in early responses to particular metals on plant conditions from a long-term perspective.
Phenolic Compounds and Organic Acid Composition of Syringa vulgaris L. Flowers and Infusions
The study aimed to determine the content of phenolic compounds (phenolic acids and flavonoids) and organic acids in dried flowers and water infusions of non-oxidised and oxidised flowers from four lilac cultivars. The diversity in the total phenolic and flavonoid content was in the flowers (18.35–67.14 and 2.03–2.65 mg g−1 DW, respectively) and infusions (14.72–47.78 and 0.20–1.84 mg per 100 mL infusion, respectively) depending the flower colour and form (oxidised and non-oxidised). Phenolic compounds and organic acids were susceptible to oxidation. Compared to infusions, flowers had more phenolic compounds and organic acids. The highest content of most phenolic compounds was confirmed for non-oxidised purple flowers (up to 7825.9 µg g−1 DW for chlorogenic acid) while in infusions for non-oxidised white flowers (up to 667.1 µg per 100 mL infusions for vanillic acid). The phenolic profile of the infusions was less diverse than that of flowers. The scavenging ability ranged from 52 to 87%. The highest organic acid content in flowers was for oxidised blue and purple flowers (2528.1 and 2479.0 µg g−1 DW, respectively) while in infusions the highest organic acid content was for oxidised purple flowers (550.1 µg per 100 mL infusions).