The general aim of this work was to compare the leaf-level responses of different protective components to water deficit and high temperatures in Quercus cerris L. and Quercus robur L. Several biochemical components of the osmotic adjustment and antioxidant system were investigated together with changes in hormones. Q. cerris and Q. robur seedlings responded to water deficit and high temperatures by: (1) activating a different pattern of osmoregulation and antioxidant mechanisms depending on the species and on the nature of the stress; (2) upregulating the synthesis of a newly-explored osmoprotectant, dimethylsulphoniopropionate (DMSP); (3) trading-off between metabolites; and (4) modulating hormone levels. Under water deficit, Q. cerris had a higher antioxidant capacity compared to Q. robur, which showed a lower investment in the antioxidant system. In both species, exposure to high temperatures induced a strong osmoregulation capacity that appeared largely conferred by DMSP in Q. cerris and by glycine betaine in Q. robur. Collectively, the more stress-responsive compounds in each species were those present at a significant basal level in non-stress conditions. Our results were discussed in terms of pre-adaptation and stress-induced metabolic patterns as related to species-specific stress tolerance features.

Clopyralid and imazamox are successfully used for weed control during the first years of regeneration of pedunculate oak forests. Hence, the question that arises is how these herbicides affect microorganisms, especially the activity of dehydrogenase enzyme, when they reach the soil. Two study sites were selected in regenerated pedunculate oak forests, and the two herbicides were applied in two doses that are used for weed control (clopyralid, 100 g a.i. ha⁻¹ and 120 g a.i. ha⁻¹; imazamox, 40 g a.i. ha⁻¹ and 48 g a.i. ha⁻¹). The effect of the herbicides was evaluated 7, 14, 21, 30, and 60 days after application. A significant reduction in dehydrogenase activity was found on days 7 and 14 at both sites. However, after 14 days there was a recovery of dehydrogenase activity for all treatments such that the values obtained on day 21 did not differ from the control values. The effect of clopyralid and imazamox on dehydrogenase activity was not dose-dependent. Dehydrogenase activity also depended on soil properties, soil sampling time and climatic conditions during the investigation years. The results show that clopyralid and imazamox can reduce soil dehydrogenase activity, but this effect is transient. This can be attributed to the ability of microorganisms to overcome the stress caused by the herbicide by developing the capability to utilize herbicides as a nutrient source and proliferating in such an environment.

Aim of study: In the present paper the nature and level of co-dependence between leaf functional traits and intrinsic water-use efficiency (WUEi) were studied in one-year-old Quercus robur L. seedlings, grown in a common garden experiment under moderate drought conditions. The study was established to identify those traits that might potentially be utilized to improve leaf-level WUEi, and therefore be used in breeding programmes to enhance drought adaptation of Q. robur.Area of study: The study was carried out at the common garden site within the UNESCO Biosphere Reserve Mura-Drava-Danube.Material and methods: The study involved one-year-old seedlings of eight half-sib lines of Q. robur. Eighteen leaf parameters were analyzed; i.e. physiological, biochemical, morphological and anatomical. The data were processed using multivariate statistical methods: a) principal component analysis, b) stepwise regression analysis, and c) path coefficient analysis.Main results: The results showed that leaf stomata traits, particularly stomatal density (SD), and leaf dry mass per unit leaf area (LMA) were the most important traits, closely associated with WUEi. Stomatal density achieved the highest score on PC1 (0.825), in which WUEi had the highest loading (0.920), as well. SD was also included first in stepwise regression model.Research highlights: These results demonstrate that under moderate water stress WUEi in Q. robur half-sib lines were mainly the result of the plants’ structural acclimation to surrounding environmental conditions. Keywords: Quercus robur L.; half-sib line; intrinsic water-use efficiency; leaf functional traits.

In this study, five poplar clones (Populus deltoides cl. PE19/66, cl. S1-8, cl. 135/81, and Populus × euramericana cl. I-214, cl. Pannonia) and two white willow clones (Salix alba cl. 380, cl. 107/65-9) were tested in pot trials. The aim was to evaluate their potential for phytoextraction of nine heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in three substrates, two based on soil from landfills near Belgrade and Novi Sad, and one control treatment based on nursery soil. The shoot content of all analyzed heavy metals was the highest in the BG substrate with the highest content of heavy metals and the lowest in the control substrate. White willow clone 107/65-9 achieved the highest accumulation of Cd, Cr, Fe, Ni and Pb and along with another willow clone 380 is found to act as generalists. Poplar clones performed more as specialists: I-214 and Pannonia for copper, PE 19/66 for manganese and S1-8 for nickel and zinc. Considerable differences among examined clones in heavy metal accumulation and reaction to substrates should be taken into consideration in further pot and field trials as well as in phytoremediation projects on landfills.

Halomorphic soils cover a significant area in the Vojvodina region and represent ecological and economic challenges for agricultural and forestry sectors. In this study, four economically important Serbian poplar clones were compared according to their biochemical and transcriptomic responses towards mild and severe salt stress to select the most tolerant clones for afforestation of halomorphic soils. Three prospective clones of Populus deltoides (Bora-B229, Antonije-182/81 and PE19/66) and one of hybrid genetic background P. nigraxP. deltoides, e.g., P. x euramericana (Pannonia-M1) were hydroponically subjected to NaCl as a salt stress agent in a concentration range from 150 mM to 450 mM. Plant responses were measured at different time periods in the leaves. Biochemical response of poplar clones to salt stress was estimated by tracking several parameters such as different radical scavenging capacities (estimated by DPPH, FRAP and ABTS assays), accumulation of total phenolic content and flavonoids. Furthermore, accumulation of two osmolytes, glycine betaine and proline, were quantified. The genetic difference of those clones has been already shown by single nucleotide polymorphisms (SNPs) but this paper emphasized their differences regarding biochemical and transcriptomic salt stress responses. Five candidate genes, two putative poplar homologues of GRAS family TFs (PtGRAS17 and PtGRAS16), PtDREB2 of DREB family TFs and two abiotic stress-inducible genes (PtP5SC1, PtSOS1), were examined for their expression profiles. Results show that most salt stress-responsive genes were induced in clones M1 and PE19/66, thus showing they can tolerate salt environments with high concentrations and could be efficient in phytoremediation of salt environments. Clone M1 and PE19/66 has ABA-dependent mechanisms expressing the PtP5CS1 gene while clone 182/81 could regulate the expression of the same gene by ABA-independent pathway. To improve salt tolerance in poplar, two putative GRAS/SCL TFs and PtDREB2 gene seem to be promising candidates for genetic engineering of salt-tolerant poplar clones.

Poplars and willows have been cultivated for their environmental benefits for millennia. In the present study, physiological responses were examined in three poplar and three willow clones grown in soil from the landfills near Novi Sad and Belgrade, Serbia. The experiment, conducted under controlled conditions in pots with soil directly from the landfill sites, aimed to identify the most suitable clones based on their physiological performance on examined substrates. Within the process of phyto-recurrent selection, six clones were selected for this experiment: Populus deltoides cl. PE 19/6, PE 4/68, S 1-8, and Salix alba cl. 107/65-9, 79/64-2, 380. Four physiological parameters (net photosynthesis [A], transpiration [E], water use efficiency [WUE], and stomatal conductance [gs]) were measured throughout the research. Analysis of variance revealed that certain clones exhibited superior physiological responses compared to others. The superior performance of poplar clones PE 4/68 and S 1-8 in key physiological parameters underscores their potential for improving growth, resilience, carbon sequestration, and overall ecological and economic benefits, making them valuable candidates for forestry and environmental management programs.