Evaluating Populus tremula L.

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

provided the original author(s) and the effects (height increase up to 27%, total chlorophyll increase up to 67%) and
demonstrated strong phytostabilization capacity for Pb (up to 0.54% of Pb in root
and Zn, with Zn increase up to 639% in Cd-treated S. caprea (50 µM). These
between 2005 and 2022: Pb emissions decreased by 44%, and Cd by
39% across the EU-27 Member States (De Vries et al., 2022).
Cd concentrations exceeding 1 mg/kg (Ballabio et al., 2024) while a
total of at least 10% (depending on the imposed limits, 19 or even
36%) of all tested agricultural soil samples exceeded the limits for the
notable gap in researching early seedling establishment and response needed with half-strength (50%) Hoagland’s nutrient medium.
Additionally, the study seeks to determine whether either species was contaminated with HMs – As (AsH15Na2O11, 98% purity;
functions as a hyperaccumulator of these metals, thereby Thermo Fisher, Germany), Pb (Pb(NO3)2, 99% purity; VWR
contributing to the development of more efﬁcient and sustainable International GmbH, Austria) and Cd (CdSO4, 99% purity;
HCl and NaOH) and grown in modiﬁed full-strength (100%) analyses. For the biochemical analyses, 6 fresh samples of 0.1 g were
of two metal beads. Next, 1.5 mL of 80% ethanol (v/v in water, MV
minutes. Subsequently, 10% Na2CO3 was added, and the mixture
Absorbance of the extract was measured at 470, 648, and 664 K-phosphate buffer (pH 7) and 30% H2O2. Absorbance was
The formulas and further details for the analysis were described H2O2, and 48% HF in a volume ratio of 8:3:1. The digestion process
samples darkened relative to the control. Absorbance was then solution (5 mg/L) was analyzed every 20 samples. Calibration was
measured at 550 nm to determine SOD activity. The formulas and repeated whenever the measured value deviated by more than 10%
phosphate buffer (pH 6.5), and 30% H2O2. Absorbance at 430 nm Pure Standards were used. The accuracy of elemental analysis was
and 30% H2O2. Absorbance at 290 nm was recorded at regular
using Dunn’s post hoc test (p<0.05). A 95% conﬁdence level was
1. (Sigma Aldrich), EDTA, and NADPH (Carl Roth). After adding uptake data were expressed as a mean from 3 pooled samples due
samples were then digested with a mixture of 65% HNO3, 30% μM of As resulted in complete shoot growth inhibition and severe
groups due to lack of biomass. To assess the seedlings’ ability to treated Populus seedlings, leaf concentrations ranged from 9 to 17
the TI (tolerance index) exceeded 100%, ranging from 113% to 23% to 81% across all tested concentrations (5, 25, and 50 μM),
127% (Table 1, Figure 2), indicating enhanced growth under indicating poor seedling health. TFs were relatively high, ranging
ranged from 0.01 to 0.06 (Table 1). Under Pb exposure, the BCF leaves and 317.66 to 326.14 in the roots. Similarly, P. tremula
(bioconcentration factor) for P. tremula shoots remained below 1 showed low tolerance to As (100 μM), with a TI of 69% (Figure 1,
(Table 1). The precise HM concentrations in leaves and roots for 279.9. In both cases this suggests limited As and Cd translocation
all experimental groups are presented in Table 1. Notably, all HM but signiﬁcant root accumulation (Table 1).
HMs. Cd levels in leaves ranged from 59 to 538 μg/g DW, while root analysis reveals that As exposure (100 μM) reduced shoot height
TABLE 1 Bioconcentration factor (BCF), tolerance index (TI), translocation factor (TF) and heavy metal (HM) concentrations in the leaves and roots of
and root length by 31% and 23%, respectively. In the same group, be interpreted holistically, as they can both mean enhanced stress
total chlorophyll concentration decreased by 52% (Figure 3), while and tolerance.
MDA (indicator for lipid peroxidation and thus cellular damage) The data for Cd exposure show similar trends (Table 2).
whereas antioxidant enzyme activity generally increased, except for and root lengths decreasing by 77% and 31%, respectively, at 50 μM.
34% (Table 2). Overall, the interpretation of secondary metabolite, chlorophyll content decreased at 5 μM but exhibited a hormesis
TABLE 2 Biochemical marker (total chlorophyll, carotenoid (CAR), total phenol (TPC) and total ﬂavonoid (TFC) content, malondialdehyde (MDA), soluble sugar, (SS), antioxidant enzyme (catalase (CAT),
concentrations increased, as can be noted from the TIs (Tables 1, decreases in essential elements such as Fe, Mn, and Cu, but large
33% at 100 μM Pb, while remaining steady at 50 and 200 μM Overall, Pb has a more positive effect on element uptake in both
levels were slightly elevated at 100 μM (37%) and exhibited a interactions in the leaves, yet with continued increased metal

Methods (brief)

Kingdom was analyzed using 21,682 soil samples from the LUCAS
soil module, collected in 2009. Among these samples, 5.5% contained
36%) of all tested agricultural soil samples exceeded the limits for the
Populus tremula L. and Salix caprea L. seeds were collected in measured accurately without disrupting growth. Tolerance index
when roots emerged the seedlings were transferred to moist The aboveground and root biomass of the seedlings were collected
HCl and NaOH) and grown in modiﬁed full-strength (100%) analyses. For the biochemical analyses, 6 fresh samples of 0.1 g were
Ca(NO3)2×4H2O, 1.86 mM MgSO4×7H2O, 1 mM NH4H2PO4, 46 experimental group. Each sample was comprised of smaller
mM H3BO3, 9 mM MnCl2×4H2O, 8.99 mM C12H12Fe2O18, 0.76 mM samples taken from the biomass of the whole group. The samples
XP2003S DR, Switzerland). Three samples of ~0.2-0.4 g were taken in detail previously (Beniušytė et al., 2023). Total chlorophyll
Offenburg, Germany) with 96-well microplates. A detailed list of Soluble sugars were quantiﬁed by mixing the sample with
For each experimental group, three 0.1 g samples were
For enzyme activity assays, three 0.1 g samples of fresh biomass
collected and used for the analysis of total chlorophyll, CAR,
preserve sample integrity. The formulas and further details for the
The formulas and further details for the analysis were described H2O2, and 48% HF in a volume ratio of 8:3:1. The digestion process
SOD activity was assessed by mixing the crude extract with a root samples were determined using inductively coupled plasma
reaction buffer containing K-phosphate buffer (pH 7.8), methionine optical emission spectrometry (ICP-OES, Optima 8000,
was exposed to white light (irradiance 30 mmol m-² s-¹) until the of Reference (BCR). To monitor ICP-OES signal drift, a control

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Verification notes

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised