1. Differences in bark anatomy between stem and branches of Olea europaea L.Jožica Gričar, Klemen Eler, 2025, izvirni znanstveni članek Povzetek: In addition to morphological characteristics, bark anatomy can provide a more detailed picture of the function of different bark tissues. In the current study, we examined and compared the bark anatomy of the stem and branches of 20-year-old Olea europaea L. We hypothesised that there are differences in bark anatomical traits between stem and branches, which reflect their functional differences in a tree. We found that the widths of bark, phloem + cortex, and periderm significantly differed in the stem and branches; all tissues were wider in the stem. The size and area of the sieve tubes and the proportion of sclerenchyma in the oldest part of the phloem + cortex differed in the stem and the branches. At the same time, numerous similarities in the stem and branch bark anatomy were observed: (1) annual phloem increments could not be determined in the youngest phloem adjacent to the cambium; (2) a distinction between non-conducting and conducting phloem was not possible because the collapse of sieve tubes in non-conducting phloem was not prominent enough to be determined visually; (3) dilatation of rays and axial parenchyma was locally clearly visible; (4) the proportion of phloem and cortex changed with distance from the cambium; secondary phloem constituted the entire bark tissue adjacent to the cambium, while cortex prevailed next to the periderm and (5) phelloderm width did not change with bark age. Differences in the bark structure of the stem and branches of olive trees imply functional differences between these two tree parts and point to different ecological contexts. Moreover, branch bark trait values cannot be used to extrapolate to the main stem bark (or vice versa). Differences support previous studies that have reported that different tree parts are exposed to different microenvironments.
Ključne besede: conducting phloem, cortex, increment, non-conducting phloem, phelloderm, periderm, sclerenchyma, sieve tubes
Objavljeno v DiRROS: 14.03.2025; Ogledov: 649; Prenosov: 1603
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2. Phloem : a missing link in understanding tree growth response in a changing environmentJožica Gričar, 2024, izvirni znanstveni članek Povzetek: Although the activities of various tree organs and tissues are under different environmental and internal constraints, they need to be coordinated to ensure whole-tree functioning. Dusart et al. (2024) conducted a heating experiment on branches of Juglans regia saplings during the entire growing season to examine the effect of temperature on primary (bud) and secondary (xylem) growth. They found that primary and secondary meristems responded asynchronously to elevated temperature, which suggests that lack of coordination mechanisms between primary and secondary growth at crown scale could have a potential impact on canopy and tree architecture.
Ključne besede: phloem, wood anatomy, tree growth, angiosperms, bark, meristem, non-structural carbohydrates, primary growth, radial growth, secondary growth, temperature, xylem
Objavljeno v DiRROS: 05.12.2024; Ogledov: 277; Prenosov: 202
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3. Differences in xylem and phloem structure in living stumps of Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.)Jožica Gričar, Miha Drolc, Peter Prislan, Helena Šircelj, 2024, izvirni znanstveni članek Povzetek: Living stumps reported in many tree species were the first, circumstantial evidence of root grafting. Although stump overgrowth has been extensively studied in various tree species, anatomical observations have mainly focused on the xylem part. Here, we investigated the xylem and phloem structure in living stumps of two conifer species: Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.). The mechanism of wound closure was similar in the two species, however, there were differences in the structure of wound tissues in wood and bark. Immediately after the injury, a callus consisting of parenchymal cells was formed, followed by wound-wood with wide increments. In addition, the wood structure and morphology of tracheids were changed. Tracheids lost their typical elongated and tapering structure; instead, numerous crooked and forked tracheids were present. Traumatic resin canals were present in both species but were more abundant in P. abies, which also had normal resin canals. While the structure of the xylem growth rings eventually normalized in both species, the width of the annual xylem increments was diminished. In both species, the typical structure of annual phloem increment was lost in the non-collapsed phloem and sclereids were very abundant in the collapsed phloem. In A. alba, the collapsed phloem was rich in swollen parenchyma cells containing blue-stained contents, while in P. abies, numerous large traumatic resin canals were conspicuous. The study showed that similar patterns of vascular tissue restoration exist in A. alba and P. abies in response to tree felling. However, there are certain species-specific peculiarities in the wood and phloem anatomical response, which might affect long-term stump functioning and survival.
Ključne besede: wood physiology, phloem, xylem, Norway spruce, Picea abies, silver fir, Abies alba
Objavljeno v DiRROS: 03.12.2024; Ogledov: 403; Prenosov: 1533
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4. Temporal and spatial variability of phloem structure in Picea abies and Fagus sylvatica and its link to climateJožica Gričar, Jernej Jevšenak, Kyriaki Giagli, Klemen Eler, Dimitrios Tsalagkas, Vladimir Gryc, Hanuš Vavrčík, Katarina Čufar, Peter Prislan, 2024, izvirni znanstveni članek Povzetek: Using a unique 8-year data set (2010–2017) of phloem data, we studied the effect of temperature and precipitation on the phloem anatomy (conduit area, widths of ring, early and late phloem) and xylem-ring width in two coexisting temperate tree species, Picea abies and Fagus sylvatica, from three contrasting European temperate forest sites. Histometric analyses were performed on microcores taken from tree stems in autumn. We found high interannual variability and sensitivity of phloem anatomy and xylem-ring widths to precipitation and temperature; however, the responses were species- and site-specific. The contrasting response of xylem and phloem-ring widths of the same tree species to weather conditions was found at the two Slovenian sites generally well supplied with precipitation, while at the driest Czech site, the influence of weather factors on xylem and phloem ring widths was synchronised. Since widths of mean annual xylem and phloem increments were narrowest at the Czech site, this site is suggested to be most restrictive for the radial growth of both species. By influencing the seasonal patterns of xylem and phloem development, water availability appears to be the most important determinant of tissue- and species-specific responses to local weather conditions.
Ključne besede: wood anatomy, early phloem, European beech, late phloem, Norway spruce, sieve element area, xylem-ring width
Objavljeno v DiRROS: 19.01.2024; Ogledov: 891; Prenosov: 517
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5. Priorities for bark anatomical research : study venues and open questionsIlana Shtein, Jožica Gričar, Simcha Lev-Yadun, Alexei Oskolski, Marcelo R. Pace, Julieta A. Rosell, Alan Crivellaro, 2023, izvirni znanstveni članek Ključne besede: bark, anatomy, cork, dilatation, periderm, phellogen, phenology, phloem, methods, ecology
Objavljeno v DiRROS: 16.05.2023; Ogledov: 925; Prenosov: 539
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6. Transition dates from earlywood to latewood and early phloem to late phloem in Norway SpruceJožica Gričar, Katarina Čufar, Klemen Eler, Vladimir Gryc, Hanuš Vavrčík, Martin De Luis, Peter Prislan, 2021, izvirni znanstveni članek Povzetek: Climate change will affect radial growth patterns of trees, which will result in different forest productivity, wood properties, and timber quality. While many studies have been published on xylem phenology and anatomy lately, little is known about the phenology of earlywood and latewood formation, also in relation to cambial phenology. Even less information is available for phloem. Here, we examined year-to-year variability of the transition dates from earlywood to latewood and from early phloem to late phloem in Norway spruce (Picea abies) from three temperate sites, two in Slovenia and one in the Czech Republic. Data on xylem and phloem formation were collected during 2009-2011. Sensitivity analysis was performed to determine the specific contribution of growth rate and duration on wood and phloem production, separately for early and late formed parts. We found significant differences in the transition date from earlywood to latewood between the selected sites, but not between growth seasons in trees from the same site. It occurred in the first week of July at PAN and MEN and more than two weeks later at RAJ. The duration of earlywood formation was longer than that of latewood formation; from 31.4 days at PAN to 61.3 days at RAJ. In phloem, we found differences in transition date from early phloem to late phloem also between the analysed growth seasons; from 2.5 weeks at PAN to 4 weeks at RAJ Compared to the transition from earlywood to latewood the transition from early phloem to late phloem occurred 25-64 days earlier. There was no significant relationship between the onset of cambial cell production and the transition dates. The findings are important to better understand the inter-annual variability of these phenological events in spruce from three contrasting temperate sites, and how it is reflected in xylem and phloem anatomy.
Ključne besede: Picea abies, xylem formation, phloem formation, cambium, tracheid, sieve cell, conifer, temperate environment
Objavljeno v DiRROS: 22.03.2021; Ogledov: 1773; Prenosov: 1266
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7. The effect of crown social class on bark thickness and sapwood moisture content in Norway spruceLuka Krajnc, Jožica Gričar, 2020, izvirni znanstveni članek Povzetek: The research study examined the effect of tree properties (crown social class, diameter at breast height (DBH), and tree height) on bark thickness (BT) and sapwood moisture content (SMC) in Norway spruce (Picea abies (L.) H. Karst.). Both examined variables were shown to be positively affected by DBH and tree height. The relationship between DBH and SMC varied among crown social classes, while the relationship between DBH and BT was relatively constant across crown social classes. Crown social class had a relatively small effect on BT and SMC, having a more pronounced effect on SMC than on BT. The relationship between tree height and BT did not vary across crown social classes, while the relationship between SMC and tree height was found to change slightly across crown social classes. Measurements of BT and SMC in the field are affordable, fast, and easy to use. Both variables could potentially be used to improve predictions of bark beetle attacks, as they reflect the physiological state of an individual tree.
Ključne besede: Picea abies, tree diameter, tree height, crown social class, phloem, sapwood
Objavljeno v DiRROS: 14.01.2021; Ogledov: 1815; Prenosov: 1434
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8. Timeline of leaf and cambial phenology in relation to development of initial conduits in xylem and phloem in three coexisting sub-Mediterranean deciduous tree speciesJožica Gričar, Andreja Vedenik, Gregor Skoberne, Polona Hafner, Peter Prislan, 2020, izvirni znanstveni članek Povzetek: It is unclear how the anticipated climate change will affect the timing of phenology of different tree organs/tissues and thus the whole-tree functioning. We examined the timing of leaf phenology and secondary growth in three coexisting deciduous tree species (Quercus pubescens Willd., Fraxinus ornus L. and Ostrya carpinifolia Scop) from a sub-Mediterranean region in 2019. In addition, we investigated the relationship between leaf and cambial phenology and the onset of the potential functioning of initial conduits, as determined by the completed differentiation process (vessels) or final size (sieve tubes). For this purpose, leaf development was monitored and the microcores of cambium and the youngest phloem and xylem increments were repeatedly collected at 7-10-day intervals during the growing season. The results revealed differences in the timing of leaf development and seasonal radial growth patterns in spring among the studied tree species, depending on wood porosity. We found that cambial cell production started in all cases in the first half of March. However, in ring-porous Q. pubescens and F. ornus, radial growth in the stem occurred more than a month before buds were swollen, whereas in diffuse-porous O. carpinifolia, these two events were detected at almost the same time. The end of cambial cell production occurred earliest in F. ornus (mid-July) and two weeks later also in the other two species. The widest initial earlywood vessels and early phloem sieve tubes were found in Q. pubescens, the narrowest initial earlywood vessels in O. carpinifolia and the narrowest early phloem sieve tubes in F. ornus. This indicates differences in the e%ciency of conducting systems among the studied species. This novel approach of studying phloem phenology and anatomy in relation to leaf and xylem development contributes to a better understanding of how different tree species adapt their structure of secondary vascular tissues in response to environmental change.
Ključne besede: Quercus pubescens, Fraxinus ornus, Ostrya carpinifolia, earlywood, early phloem, vessel, sieve tube, radial growth
Objavljeno v DiRROS: 21.10.2020; Ogledov: 1829; Prenosov: 1297
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9. Post-fire effects on development of leaves and secondary vascular tissues in Quercus pubescensJožica Gričar, Polona Hafner, Martina Lavrič, Mitja Ferlan, Nives Ogrinc, Bor Krajnc, Klemen Eler, Dominik Vodnik, 2020, izvirni znanstveni članek Povzetek: An increased frequency of fire events on the Slovenian Karst is in line with future climate-change scenarios for drought-prone environments worldwide. It is therefore of the utmost importance to better understand tree-fire-climate interactions for predicting the impact of changing environment on tree functioning. To this purpose, we studied the post-fire effects on leaf development, leaf carbon isotope composition (%13C), radial growth patterns and the xylem and phloem anatomy in undamaged (H-trees) and fire-damaged trees (F-trees) of Q. pubescens with good re-sprouting ability in spring 2017, the growing season after a rangeland fire in August 2016. We found that the fully developed canopy of F-trees reached only half of the LAI values measured in H-trees. Throughout the season, F-trees were characterised by higher water potential and stomatal conductivity and achieved higher photosynthetic rates compared to unburnt H-trees. The foliage of F-trees had more negative %13C values than those of H-trees. This reflects that F-trees less frequently meet stomatal limitations due to reduced transpirational area and more favourable leaf-to-root ratio. In addition, the growth of leaves in F-trees relied more on the recent photosynthates than on reserves due to the fire disturbed starch accumulation in the previous season. Cambial production stopped 3 weeks later in F-trees, resulting in 60% and 22% wider xylem and phloem increments, respectively. A novel approach by including phloem anatomy in the analyses revealed that fire caused changes in conduit dimensions in the early phloem but not in the earlywood. However, premature formation of the tyloses in the earlywood vessels of the youngest two xylem increments in F-trees implies that xylem hydraulic integrity was also affected by heat. Analyses of secondary tissues showed that although xylem and phloem tissues are interlinked changes in their transport systems due to heat damage are not necessarily coordinated.
Ključne besede: pubescent oak, cambium, radial growth, xylem, phloem, anatomy, sub-Mediterranean
Objavljeno v DiRROS: 19.03.2020; Ogledov: 3251; Prenosov: 1810
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10. Odziv kambija navadne smreke (Picea abies) na ogrevanje in hlajenje deblaJožica Gričar, Martin Zupančič, Katarina Čufar, Primož Oven, 2004, izvirni znanstveni članek Povzetek: Proučili smo vpliv eksperimentalnega ogrevanja in hlajenja dela debla navadne smreke (Picea abies) na kambijevo aktivnost in celično diferenciacijo. Poskusasta potekala 30 dni; ogrevanje od 29.3.2004 do 3.5.2004, hlajenje pa od14.6.2004 do 20.7.2004. Vzorce floema, kambija in ksilema smo iz dreves odvzeli vsakih 10 dni, pripravili prečne prereze tkiv in preparate opazovali ssvetlobnim mikroskopom. Lokalno ogrevanje je po 10 dneh induciralo delitveno aktivnost kambija na floemsko stran, po 20 dneh pa tudi na ksilemsko. Po 30 dneh je pri ogrevanem vzorcu nastalo do 15 celic ranega lesa. V tem času se jeredna delitvena aktivnost kambija pri kontrolnem drevesu šele začela. Odziv kambija na hlajenje debla je bil manj izrazit. Anatomskih razlik med kontrolnim in hlajenim vzorcem po 10 in 20 dneh ni bilo. Po 30 dneh je pri hlajenem vzorcu začel nastajati kasni les, pri kontrolnem drevesu pa šele prehodni rani-kasni les. S poskusom smo demonstrirali, da je mogoče pri smrekiz umetnim ogrevanjem in hlajenjem debla vplivati na ksilo- in floemogenezo.
Ključne besede: navadna smreka, Picea abies, kambij, celična diferenciacija, ksilem, floem, ogrevanje, hlajenje, svetlobna mikroskopija, Norway spruce, cambium, cell differentiation, xylem, phloem, heating, cooling, light microscopy
Objavljeno v DiRROS: 12.07.2017; Ogledov: 5378; Prenosov: 2283
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