Abstract
Reactivation of axial water flow in ring-porous species is a complex process related to stem water content and developmental stage of both earlywood-vessel and leaf formation. Yet empirical ...evidence with non-destructive methods on the dynamics of water flow resumption in relation to these mechanisms is lacking. Here we combined in vivo magnetic resonance imaging and wood-anatomical observations to monitor the dynamic changes in stem water content and flow during spring reactivation in 4-year-old pedunculate oaks (Quercus robur L.) saplings. We found that previous year latewood vessels and current year developing earlywood vessels form a functional unit for water flow during growth resumption. During spring reactivation, water flow shifted from latewood towards the new earlywood, paralleling the formation of earlywood vessels and leaves. At leaves' full expansion, volumetric water content of previous rings drastically decreased due to the near-absence of water in fibre tissue. We conclude (i) that in ring-porous oak, latewood vessels play an important hydraulic role for bridging the transition between old and new water-conducting vessels and (ii) that fibre and parenchyma provides a place for water storage.
Oak bark has been used since ancient times in Europaen ethnomedicine because of its adstringent, antimicrobial and hemostatic features, e.g. as a remedy for the treatment of wounds and skin diseases.
...Oak bark tannins are considered as bioactive natural products, interacting with surface proteins of mucous membranes and might be beneficial for the treatment of allergic diseases. This study investigated the effect of an oak bark decoction (OBD) and isolated tannin fractions on the degranulation capacity and cytokine/chemokine release from rat basophilic cells and human mast cells in vitro, which are essential for the initiation of early- and late-phase allergic reactions.
By chromatographic separation on Sephadex® LH-20 high- and low-molecular weight tannins were separated from OBD and the tannin composition analyzed by HPLC(DAD)-MSn. Then, the OBD and its fractions were tested in degranulation (β-hexosaminidase activity) of allergen-specific-activated basophilic cells in a photometric assay.
The OBD and the high-molecular tannin fraction showed a dose-dependent inhibition of cell degranulation. Furthermore, the OBD and particularly its high molecular weight tannin fraction exhibited an inhibitory activity on the IL-8-, IL-6- and TNF-α-secretion from stimulated human mast cells, detected and quantified by ELISA.
The OBD and its high-molecular weight tannins revealed an impact on allergic mediator release of basophilic cells and human mast cells and thereby provide a rationale for the topical treatment with OBD preparations.
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We analyze interannual to multi-decadal growth variations of 555 oak trees from Central-West Germany. A network of 13 pedunculate oak (Quercus robur L.) and 33 sessile oak (Quercus petraea (Matt.) ...Liebl.) site chronologies is compared with gridded temperature, precipitation, cloud-cover, vapor pressure and drought (i.e., Palmer Drought Severity Index, PDSI) fluctuations. A hierarchic cluster analysis identifies three groups for each oak species differentiated by ecologic settings. When high precipitation is primarily a characteristic for one Q. robur and one Q. petraea cluster, the other clusters are more differentiated by prevailing temperature conditions. Correlation analysis with precipitation and vapor pressure reveals statistically significant (P ≤ 0.05) correlations for June (r = 0.51) and annual (r = 0.43) means. Growth of both species at dry sites correlates strongly with PDSI (r = 0.39, P ≤ 0.05), and weakly with temperature and cloud-cover. In natural stands, Q. robur responds more strongly to water depletion than Q. petraea. Twenty-one-year moving correlations show positive significant growth response to both PDSI and precipitation throughout the 20th century, except for the 1940s - an anomalously warm decade during which all oak sites are characterized by an increased growth and an enhanced association with vapor pressure and temperature. We suggest that the wider oak rings that are exhibited during this period may be indicative of a nonlinear or threshold-induced growth response to drought and vapor pressure, and run counter to the general response of oak to drought and precipitation that normally would result in suppressed growth in a warmer and drier environment. As the wide rings are formed during the severe drought period of the 20th century, a complex model seems to be required to fully explain the widespread oak growth. Our results indicate uncertainty in estimates of future growth trends of Central European oak forests in a warming and drying world.
Key message
Efflux-based estimates of stem respiration in oak trees during the dormant season were biased by axial diffusion of locally respired CO
2
. Light-induced axial CO
2
diffusion along the ...stem due to woody tissue photosynthesis may lead to equivocal estimates of stem respiratory coefficients during the dormant season, which are generally used to estimate maintenance respiration throughout the year.
Context
Stem CO
2
efflux (E
A
) does not reflect respiratory rates of underlying tissues. Recent research has focused on the significance of CO
2
transport via the transpiration stream. However, no studies have yet addressed the potential role of light-induced axial CO
2
diffusion on E
A
during the dormant season when there is no transpiration.
Aims
This study investigated to which extent woody tissue photosynthesis and axial diffusion of respired CO
2
affect E
A
during the dormant season.
Methods
E
A
was measured in a stem cuvette on dormant oak trees in a growth chamber at constant temperature. Different rates of axial CO
2
diffusion were induced by woody tissue photosynthesis by means of illuminating stem sections at varying distances from the stem cuvette, while light was excluded from the remainder of the tree.
Results
Axial diffusion of respired CO
2
led to reductions in E
A
of up to 22% when the stem section closest to the cuvette was exposed to light.
Conclusion
Dormant-season efflux-based estimates of stem respiration might be biased by axial diffusion of respired CO
2
, particularly in open forest stands with sufficient light penetration. Consequently, this may lead to ambiguous estimates of dormant season E
A
coefficients (Q
10
and E
A_0
) generally used to estimate maintenance respiration throughout the year.
In trees, stem diameter variations are related to changes in stem water content, because internally stored water is depleted and replenished over a day. To confirm this relationship, non-invasive ...magnetic resonance imaging (MRI) was combined with point dendrometer measurements in three actively transpiring oak (Quercus roburL.) trees. Two of these oak trees were girdled to study the stem increment above the girdling zone. MRI images and micrographs of stem cross-sections revealed a close link between the water distribution and the anatomical features of the stem. Stem tissues with the highest amount of water were physiologically the most active ones, being the youngest differentiating xylem cells, the cambium and the youngest differentiating and conductive phloem cells. Daily changes in stem diameter corresponded well with the simultaneously MRI-measured amount of water, confirming their strong interdependence. MRI images also revealed that the amount of water in the elastic bark tissues, excluding cambium and the youngest phloem, contributed most to the daily stem diameter changes. After bark removal, an additional increase in stem diameter was measured above the girdle. This increase was attributed not only to the cambial production of new cells, but also to swelling of existing bark cells. In conclusion, the comparison of MRI and dendrometer measurements confirmed previous interpretations and applications of dendrometers and illustrates the additional and complementary information MRI can reveal regarding water relations in plants.
The objective was to examine the effects of optimal leaf nitrogen levels > 2.0% and suboptimal levels ˂ 2.0%, nitrogen nutrition on net photosynthetic rate, stem diameter increment, height growth ...increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought stress. According to the results, moderate drought stress significantly reduced net photosynthetic rate, stem diameter increment and height growth increment, while acorn mass was not affected. Suboptimal nitrogen nutrition significantly reduced the net photosynthetic rate and stem diameter increment only in the wet year, acorn mass in both wet and dry years, while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either year. The results indicate that optimal nitrogen levels can stimulate photosynthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought stress. Moreover, the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition, while for acorn development, it is the more dominant stressor.
U testu provenijencija hrasta lužnjaka (
Quercus robur
L.) u Bosni i Hercegovini koji je osnovan 2009. godine istraživana je varijabilnost visina biljaka i promjera vrata korijena na biljkama iz 27 ...provenijencija. Osim toga, analizirane su i korelacije između visina stabala i promjera vrata korijena s morfološkim svojstvima listova iz prirodnih populacija. Sjeme za osnivanje testova provenijencija, kao i listovi koji su korišteni u morfometrijskoj analizi, sakupljeni su u istim populacijama. Provedenim istraživanjima utvrđene su statistički značajne razlike za svojstvo visine i promjera vrata korijena. Varijabilnost je potvrđena i Duncan-ovim testom, i to na način da su biljke s obzirom na svojstvo visina grupirane u 11 skupina te s obzirom na svojstvo promjer vrata korijena u četiri skupine. Klasterskom analizom nije utvrđeno grupiranje populacija s obzirom na geografske i ekološke udaljenosti populacija. Korelacijskom analizom potvrđena je statistički značajna povezanost između visine biljaka i promjera vrata korijena te između morfoloških svojstava listova i visine biljaka i promjera vrata korijena. Dobiveni rezultati upućuju na to da se na temelju određenih morfoloških svojstava može provoditi selekcija provenijencija u mlađim fazama razvoja.
Pedunculate oak (
Quercus robur
L., Fagaceae) is an economically and ecologically valuable species that has almost completely disappeared from the territory of Bosnia and Herzegovina due to over-exploitation, and through reintroduction and breeding activities it should be returned and protected in areas optimal for its growth. This study aimed to determine whether there is a correlation between the
morphological traits of pedunculate oak leaves in populations where the seed for establishing provenance test was collected with the root collar diameter and height of plants growing in the provenance test.
In the first part of this study, leaves from 27 natural populations of pedunculate oak throughout Bosnia and Herzegovina were measured (Table 1). Ten leaves per tree were measured from ten trees per population. The following traits were measured (Figure 1): K1 - leaf blade length in mm, K2 - leaf petiole length in mm, K3 - the distance of the widest part of the blade from the blade base (on the right side) in mm, K4 - width of the right half-blade at the height from K3 in mm, K5 - (maximum) width of the left half-blade in mm, K6 - incision of the leaf from the central nerve in mm, K7 - incision of the blade base. The second part of the research includes the measurement of heights and root collar diameters of pedunculate oak plants in the provenance test in Žepče in the spring of 2020. The provenance test was established in 2009 from seeds from the same populations and from the same trees from which the leaf material was collected for morphometric analysis. Data were processed in the statistical program SPSS 26.0. Descriptive analysis, analysis of variance, multiple Duncan test, and cluster analysis using the Average Linkage Method for the traits of the height and root collar diameter of plants in the provenance test were performed. A correlation analysis between the morphological traits of the leaves in the populations and the growth of provenances in the provenance test using the Pearson coefficient was also performed. Mutual correlations of leaf traits, correlations between height and root collar diameter of plants in the provenance test, and correlations between leaf traits and height and root collar diameter of plants in the provenance test were calculated.
Analysis of variance for the height and root collar diameter showed statistically significant differences among the investigated provenances, which was confirmed by Duncan’s test (Table 2, 3 and 4). The highest average value of plant height for 2020 had provenance Drvar (445.8 cm), followed by Jelah and Vinac, while the lowest average value had provenance Visoko - Muhašinovići (262.3 cm) (Figure 2). Overflow of provenances was registered for the height. The highest average value of root collar diameter had provenance Živinice (Figure 3), followed by the provenances Jelah and Drvar (10.7 cm), while the lowest value had provenance Nević polje (7.4 cm). The results of the conducted descriptive statistical analysis for morphological leaf traits are shown in Table 5. There was no clear pattern in the formation of groups (Figure 4), which is a consequence of the earlier historical negative effect of man on the pedunculate oak population. A significant positive correlation between height and root collar diameter was recorded at the 0.01 level (Table 6). A positive significant correlation was also registered between the height and leaf traits, except for the petiole length which did not show a significant correlation. A positive correlation was registered between the root collar diameter and all investigated leaf traits except for the petiole length and the incision of the leaf blade base of the leaf blade.
Given the obtained variability among the studied provenances, as well as significant correlations of height and root collar diameter of plants in provenance test with leaf traits, the obtained results should be used in the selection of seed trees and stands, i.e., planning measures for conservation and reintroduction of pedunculate oak in Bosnia and Herzegovina.
•Oil yield in the oak acorns of Q. rubra reached 20.1–24.0% vs 3.1–6.3% in Q. robur.•Q. rubra and Q. robur acorn oils are rich in oleic and linoleic acids.•The β and γ-tocopherol are predominated ...forms in Q. rubra and Q. robur, respectively.•β-Sitosterol constituted over 60% of total phytosterols in acorn oil of both species.•PCA analysis may help to distinguish the acorn oils recovered from different species.
The acorns (fruits) of the oak species Quercus rubra L. and Quercus robur L., grown over the world mainly in forests and parks, are usually not collected or utilised, therefore represent a potentially cheap/free source of plant material with potential applications in the processing industry. In the present study, oil recovery and composition from acorns collected from Q. rubra (n=6) and Q. robur (n=7) individuals was evaluated. Oil yields from Q. robur and Q. rubra acorns ranged from 3.1 to 6.3% and 20.1–24.0%, respectively. In the oils of both species C18:1 (28.4–65.7%), C18:2 (24.1–48.0%) and C16:0 (7.5–17.9%) were the main fatty acids with some differences in proportions between species. On average, β-sitosterol constituted 64.3% and 68.1% of total sterol concentration, which amounted to 244.9 and 271.4mg/100g oil in Q. robur and Q. rubra, respectively. Q. rubra acorn oil was rich in β-tocopherol (93%), while Q. robur in γ-tocopherol (96%). A nearly six-fold higher level of total tocopherol content was recorded for Q. robur relative to Q. rubra. Principal component analysis of chemical composition data confirmed their ability to distinguish between Q. robur and Q. rubra samples. The unique and high concentration of lipophilic compounds in both species, and the availability (cheap/free) of acorns, make oak fruits an interesting source of plant material for industrial applications.
Glycosyltransferase gene family 1, also known as uridine diphosphate glycosyltransferase (UGT), is the largest glycosyltransferase family in plants, playing a vital role in their growth and ...development. In this study, 244
UGT
genes with conserved PSPG motifs were identified in the genome of
Quercus robur
L. The collinearity analysis results showed that tandem repeat was the main way of
UGT
genes expansion in
Q. robur
, with 21 groups of 55 tandem repeat genes.
UGT
genes were divided into 15 subgroups A–P; group K was lost, and the gene structure and conserved domain of the same subgroup were basically the same. Cis-element analysis showed that upstream 2,000 bp promoter sequence of
UGT
genes contained light response elements, plant hormone response elements, and stress-related cis-elements, which indicated that
UGT
genes of
Q. robur
might be regulated by various metabolic pathways. In particular, some
UGT
s in group L of
Q. robur
contained a conserved promoter structure. The expression pattern analysis results demonstrated that
UGT
genes of groups B, D, E, and I were differentially expressed under
Tortrix viridana
L. stress. The expression of
UGT
s in group E decreased under stress, the expression of group L increased, and that of genes in groups D and B were different. The functions of
UGT
genes in E and L groups are relatively conservative, and their functions may also conserve among species. The study results have a particular reference value for further research on the function of
Q. robur UGT
genes.
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