Xylem Ring Research Articles

Leaf phenology and paleoclimatic and paleoenvironmental insights derived from Yiwupitys elegans of the Yiwu Jurassic Forest, Xinjiang, China

Many permineralized conifer stems and trunks have been documented from the Jurassic strata of the Xinjiang Uygur Autonomous Region (Xinjiang), Northwest China. Xylem anatomical studies have showed that these stems and trunks belonged to a diverse range of plants. However, the leaf phenology and the paleoclimatic and paleoenvironmental significance of these fossil plants have rarely been studied. We quantitatively analyzed the anatomical characteristics of a permineralized conifer stem—Yiwupitys elegans Gou et Feng 2023—from the Middle Jurassic Xishanyao Formation in northeastern Xinjiang, which has distinct and wide growth rings in the secondary xylem. Analyses of the Mean Sensitivity and Ring Markedness Index of the growth rings suggest that a stable paleoclimate with regular seasonal fructifications likely prevailed during the Middle Jurassic in this area. The statistical analyses of cell diameters and anatomical features of leaf traces in six successive growth rings indicate that this fossil plant was deciduous. Our study elucidates the ecophysiological characteristics of a Middle Jurassic conifer plant and provides new insights into the corresponding paleoclimate and paleoenvironment based on quantitative cellular analysis of the fossil stem.

EFFECT OF ORGANIC FERTILIZERS AND NUTRIENTS ON ANATOMICAL TRAITS OF RED BEETROOTS

A field experiment was conducted during fall season 2021-2022 In order to study the effect of soil as an agricultural medium, organic fertilizers (Vermecompost, cow manure) and foliar spraying of silicon and calcium on skin, bark and cambium ring thickness of three beetroot varieties (Red, Dark Red, and Cylindra). Seeds directly sown in the fields of Station A College of Agricultural Engineering Sciences - University of Baghdad - Al-Jadriya campus- Within RCBD a split-plot experiment, where the cultivars were the main unites, organic fertilizer, and foliar spray as the subunits, with three replicates, the number of treatments was 27. The results revealed that the triple interaction treatment of Dark Red, Vermicompost, and silicon spray V2S2F1 was superior in epidermis thickness, cortex thickness, and cambium ring thickness (55.00 μm, 78.90 μm, and 182.07μm) respectively, compared with Cylindra cultivar, soil medium, and spraying with distilled water V3S1F0, which produced the lowest averages (21.77 μm, 31.23 μm, 64.57 μm) respectively. The interaction treatment between Red cultivar, cow manure and spraying with distilled water V1S3F0 excelled in the thickness of the middle xylem ring ( 261.33 μm). Compared with the thinnest middle xylem (143.8 μm) in red cultivar roots treated with soil medium and distilled water.

Lignification in Zinnia (Zinnia elegans Jacq.) Stem Sections of Different Age: Biochemical and Molecular Genetic Traits

Lignification of the stem in zinnia provides its mechanical properties due to xylem formation, which depends on the stage of plant development and is responsible for the transport of water and minerals. The study was aimed at the lignin deposition, anatomical traits, biochemical markers of lignification, as well as the genetic regulation of this process in zinnia stem cross sections of different age during their radial growth. The anatomical traits were assessed on cross sections. The content of lignin (Cysteine-assisted sulfuric method (CASA) and the thioglycolic acid (TGA) methods), the spectrum of phenolics (by thin layer chromatography (TLC)), the total activity and the variety of class III peroxidases were determined. The expression level of genes regulating phenylpropanoids and lignin biosynthesis were assessed. We suggest that time-specific and organ-specific lignification is determined by the metabolism of phenolic compounds and depends on the expression of genes of the phenylpropanoid pathway. It was shown that in the hypocotyl, during xylem ring formation, lignification was associated with increased expression of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) genes responsible for the early stages of the phenylpropanoid pathway, and with the rise of class III peroxidases activity, including cationic isoforms. This caused increased content and diversity of phenolics in mature hypocotyl. In epicotyl, which is younger than the hypocotyl, the proportion of ferulic acid among phenolics increased, which could be considered as a marker of lignification in it. The high expression level of CAD and the activity of peroxidases, including anionic isoforms, led to accumulation of lignin. Thus, the hypocotyl and epicotyl, being characterized by different ages, differed in spectrum of phenolics, isoforms of class III peroxidases, expression of the PAL, cinnamate 4-hydroxylase (C4H), peroxidases III class (PRX), and laccase (LAC) genes, and lignin content.

A Comparative Analysis of the Hydraulic Strategies of Non-Native and Native Perennial Forbs in Arid and Semiarid Areas of China

(1) Background: Water transport systems play an important role in maintaining plant growth and development. The plasticity responses of the xylem anatomical traits of different species to the environment are different. Studies have shown that there are annual growth rings in the secondary root xylem of perennial herbaceous species. Studies on xylem anatomical traits, however, have mainly focused on woody species, with little attention given to herbaceous species. (2) Methods: We set 14 sampling sites along a rainfall gradient in arid and semiarid regions, and collected the main roots of native (Potentilla) and non-native (Medicago) perennial forbs. The xylem anatomical traits of the plant roots were obtained by paraffin section, and the relationships between the xylem traits of forbs were analyzed by a Pearson correlation. (3) Results: In the fixed measurement area (850 μm × 850 μm), the vessel number (NV) of Potentilla species was higher than that of Medicago species, while the hydraulic diameter (Dh) and mean vessel area (MVA) of Potentilla species were lower than those of Medicago species. With the increase in precipitation along the rainfall gradient, the Dh (R2 = 0.403, p = 0.03) and MVA (R2 = 0.489, p = 0.01) of Medicago species increased significantly, and NV (R2 = 0.252, p = 0.09) decreased, while the hydraulic traits of Potentilla species showed no significant trend with regard to the rainfall gradient. (4) Conclusions: The hydraulic efficiency of non-native Medicago forbs was higher than that of native Potentilla forbs, and the hydraulic safety of native Potentilla forbs was higher than that of non-native Medicago forbs. With the decrease in precipitation, the hydraulic strategies of non-native Medicago forbs changed from efficiency to safety, while native Potentilla forbs were not sensitive to variations in precipitation.

Petiole anatomy of some species of Bauhinia L. sensu lato (Leguminosae Juss.) occurring in India

The petiole is a vital part of the leaf that acts as a bridge between the lamina and stem or branch for the transport of photosynthate, minerals, nutrients and provide flexible mechanical support to the lamina. Its anatomy remains unique and species‐specific. Therefore, twelve species of Bauhinia sensu lato were investigated histologically in the present study. The disparities in the petiole outline, structure and composition of secondary xylem and presence of cell inclusions can be wisely employed for species identification. Conducting elements of the xylem and phloem were arranged as irregularly distributed individual vascular bundles in Schnella guianensis. Several vascular bundles joined to form a double ring of the xylem and phloem in Piliostigma foveolatum, P. malabaricum, P. racemosum, two species of Phanera (P. retusa, P. vahlii) and Bauhinia variegata while in the remaining species, it remained as a single ring. Other features of taxonomic importance are xylem ring that can be circular and complete and if incomplete crescent‐shaped or ‘U' shaped, arrangement of cortical bundles and their position, accumulation of tannin etc. Deposition of tannin was observed in the pith, xylem and phloem parenchyma of Piliostigma foveolatum, P. malabaricum, Bauhinia tomentosa and B. variegata and in the pith and phloem parenchyma of Phanera phoenicea, Piliostigma racemosum and Phanera scandens. Tannin was found absent in B. acuminata and B. purpurea. All these features played important role in species recognition. Structural details of the petiole are described in detail for all the investigated species using standard anatomical methods and light microscopy. Findings revealed that anatomical characteristics of the petiole are of taxonomic value for this genus and can be valuable for species identification and classification.

Adaptation of Abies fargesii var. faxoniana (Rehder et E.H. Wilson) Tang S Liu seedlings to high altitude in a subalpine forest in southwestern China with special reference to phloem and xylem traits

Key messageAbies fargesii var. faxoniana (Rehder et E.H. Wilson) Tang S Liu seedlings at high elevations compensate for the low efficiency of their water conducting system and high phloem hydraulic resistance by the enhancement in xylem:leaf area, phloem:leaf area, and phloem:xylem area.ContextMaintenance of xylem and phloem transport is particularly important for the survival and growth of trees at the treeline. How plants modify the allocation to leaf, xylem, and phloem structures to adapt to the treeline environment is an important issue.AimsThe purpose of this study was to estimate how xylem and phloem anatomy and volume as well as leaf functional traits of A. fargesii seedlings vary with elevation.MethodsWe examined elevation-related differences in a variety of phloem and xylem functional areas and hydraulic conduit diameters of A. fargesii seedlings growing at elevations between 2600 and 3200 m in the subalpine conifer forest of southwest China.ResultsXylem area, last xylem ring area, and leaf:sapwood area significantly decreased, while xylem:leaf area, phloem:leaf area, and non-collapsed phloem:xylem area significantly increased with elevation. Principal components analysis showed that xylem area, non-collapsed phloem area, and xylem:phloem area were positively correlated with growth rates.ConclusionOur results showed that A. fargesii tree seedlings at the treeline tend to facilitate growth and maintain functional water and sugar balance between stem and leaves by the enhancement in xylem:leaf area, phloem:leaf area, and phloem:xylem area, but not through differences in vessel lumen diameter.

Vincetoxicum indicum (Burm.f.) Mabb. - a case of transient abnormal secondary thickening in stem

Vincetoxicum indicum (Burm.f.) Mabb. (Syn. Tylophora indica (Burm.f.) Merr., T. asthmatica W. &A.), an important twining medicinal plant of India, was found to show a transient anomalous secondary thickening to facilitate the twisting of stem around a support. The very young stem had a continuous primary xylem cylinder, the protoxylem of which differentiated to two large bundles on the opposing sides and many smaller bundles in between. In the initial stages of maturation, the cambium outside the two large protoxylem groups behaved abnormally in producing more phloem outwards and little or no secondary xylem inwards to produce two wedge shaped phloem groups on opposite sides. The production of crescent shaped secondary xylem on the other two sides which fell at a right-angled plane resulted in bulging of these sides away from the anomalous cambium to create a rectangular stem having two broad sides which were used as the facing sides of stem against a support. As soon as the twisting nature was established, the anomaly was reversed and the anomalous cambial patches started behaving normally to produce a complete ring of secondary xylem. As this abnormal behaviour happened only during the twisting of stem, this is considered as an adaptational anomalous secondary thickening.

Plant growth shapes the effects of elevation on the content and variability of flavonoids in subalpine bilberry stands.

The study of morphological and physiological responses of shrubs to climate is crucial for the understanding of future scenarios regarding climate change. In this light, studying shrub growth and physiological acclimation along an elevation gradient might be insightful. The phenolic metabolic pathway represents a powerful tool to interpret such processes. In the South-Eastern Alps, we investigated the relationships between elevation, plant traits (i.e. age, xylem ring width, annual shoot length), plant-plant interaction (i.e. shrub cover) and flavonoids in Vaccinium myrtillus L. (leaves, berries) in stands above the treeline. The relationships were parsed within causal networks using a confirmatory path analysis. Elevation was the main driver of V. myrtillus growth, having both direct and indirect effects on the leaf flavonoid content, but this was less evident for berries. In particular, the content of foliar flavonoids showed a peak at mid-elevation and where the growth of xylem rings was intermediate, while it decreased in stands with higher shoot length. Flavonoid content variability of both leaves and berries was affected by elevation and shoot length. In berries, flavonoid variability was further related to all growth traits and shrub cover. These findings evidence that flavonoid content is influenced by both elevation and growth traits of V. myrtillus, often showing non-linear relationships. These results suggest a trait-mediated response of this plant to climate conditions as a result of trade-offs between plant growth, plant defence, environmental stress and nutrient/resource availability.

Vitality versus cambium, xylem, and phloem characteristics in Cedrus libani

Abstract In many regions, such as the Mediterranean, anticipated climate change is seen as a serious threat to tree vitality and forest productivity. Recent studies show that wood and bark structure as well as the number of dormant cambial cells bear valuable information about the growth condition and vitality of trees and thus could function as indicators to help manage forests in the future. Microcores and tree cores were sampled from stems of adult Cedrus libani trees growing at different altitudes in SW-Turkey. Trees were divided into two groups based on basal area increments: vital trees (positive growth trend), and trees of diminishing vitality (negative growth trend). Histological cross-sections were investigated for their number of dormant cambial cells as well as their xylem and phloem characteristics. We measured the widths of the conducting phloem, most recent xylem ring, earlywood, and latewood. We further calculated the ratio between the width of xylem ring and conducting phloem (XR:CPH ratio), and earlywood to latewood ratio. Vital trees had a significantly higher number of dormant cambial cells (on average 32%), higher xylem (67%), and conducting phloem (36%) widths, and a higher XR:CPH ratio (47%). The XR:CPH ratio ranged between 1.8:1 and 21.4:1. The number of dormant cambial cells was closely related to xylem and conducting phloem widths and showed a significant decrease with tree age. Altitude showed no direct effect on the measured and calculated parameters. Our results indicate the potential of dormant cambium, xylem, and phloem characteristics to assess the vitality and growth conditions of C. libani trees.

Nitrogen addition to the canopy of Castanopsis chinensis (Sprengel) Hance promoted xylem formation in a subtropical forest in China

Nitrogen addition during 4 years to the canopy of Castanopsis chinensis (Sprengel) Hance promoted xylem formation, mainly by increasing radial growth during the early growth season. Increased atmospheric nitrogen (N) deposition caused by intensive anthropogenic activities resulted in inconsistent effects on the xylem formation of trees, in N-limited boreal and temperate forests. However, the effects of N deposition on xylem formation of trees in subtropical forests are still poorly understood. The aims of the study were to (i) characterize the dynamics of xylem formation in C. chinensis in a subtropical forest in China and (ii) determine the effect on xylem formation of adding N to the canopy. From 2013 to 2016, 50 kg N ha−1 year−1 was applied over the canopy of C. chinensis at the end of each month (April to October) in a subtropical forest in southern China. Then, the dynamics of xylem formation were monitored during 2015 and 2016 using a microcore sampling approach. Xylem formation of C. chinensis lasted from February to December and the growth rate peaked during April–May. Adding N to the canopy promoted xylem width, by 21% in 2015 and 20% in 2016, mainly by increasing the growth rate during the early growth season (February to May in 2015 and February to April in 2016). Our study suggests that in a subtropical forest, canopy N addition could significantly promote the xylem ring width of C. chinensis. However, the response of tree growth to N addition showed significant difference between the early and late growth season. Therefore, further studies are needed to more comprehensively address the effect of N deposition on tree growth under global climate change.

Changes in cambial activity are related to precipitation patterns in four tropical hardwood species grown in Indonesia

Cambial activity in some tropical trees varies intra-annually, with the formation of xylem rings. Identification of the climatic factors that regulate cambial activity is important for understanding the growth of such species. We analyzed the relationship between climatic factors and cambial activity in four tropical hardwoods, Acacia mangium, Tectona grandis, Eucalyptus urophylla, and Neolamarckia cadamba in Yogyakarta, Java Island, Indonesia, which has a rainy season (November-June) and a dry season (July-October). Small blocks containing phloem, cambium, and xylem were collected from main stems in January 2014, October 2015 and October 2016, and examined with light microscopy for cambial cell division, fusiform cambial cells, and expanding xylem cells as evidence of cambial activity. During the rainy season, when precipitation was high, cambium was active. By contrast, during the dry season in 2015, when there was no precipitation, cambium was dormant. However, in October 2016, during the so-called dry season, cambium was active, cell division was conspicuous, and a new xylem ring formation was initiated. The difference in cambial activity appeared to be related to an unusual pattern of precipitation during the typically dry months, from July to October, in 2016. Our results indicate that low or absent precipitation for 3 to 4 months induces cessation of cambial activity and temporal periodicity of wood formation in the four species studied. By contrast, in the event of continuing precipitation, cambial activity in the same trees may continue throughout the year. The frequency pattern of precipitation appears to be an important determinant of wood formation in tropical trees.

Development of successive cambia and formation of secondary xylem in Suaeda nudiflora and S. fruticosa (Amaranthaceae s.l.)

Amaranthaceae s.l. and its allied families like Amaranthaceae s.s., Chenopodiaceae s.s. and Phytolaccaceae s.s. are always debated in the literature about their pattern of secondary growth; when their stem diameter increases by forming successive cambia. In the present study, development of successive cambia and differentiation of its derivatives was investigated in Suaeda fruticosa and S. nudiflora (Amaranthaceae s.l.). After primary growth, the first complete ring of cambium was formed by the successive cambium due to failure in the development of interfascicular cambium between adjacent vascular bundles. The first ring of successive cambium initiated from the parenchymatous cells (pericyclic derivatives) external to the protophloem. This newly formed cambium was functionally bidirectional and produced secondary xylem centripetally and phloem centrifugally. Subsequent renewal of cambium was observed as small segments instead of complete ring. They interconnect with existing cambium and form anastomosing network. Due to the renewal of small sectors, the secondary phloem formed by earlier cambial segments became enclosed within the secondary xylem and conjunctive tissue. Formation of vessels and sieve elements were found confined only to few fusiform cells while rest of the cambial sector exclusively produced conjunctive tissue on either side. The secondary xylem formed in the beginning of successive rings of xylem remained rayless while thick stems showed presence of heterocellular rays with several cells in height and width. Accumulation of starch along with the presence of nuclei in the xylem fibres even after deposition of the secondary wall is consistent feature in both the species.

Increasing plant diversity of experimental grasslands alters the age and growth of Plantago lanceolata from younger and faster to older and slower

The persistence of plant populations depends on the ability of individuals to cope with the conditions provided by the community. So far, it is not known whether differences in the diversity and composition of plant communities affect the age structure of plant populations or the expression of stem anatomical traits reflecting investment into plant growth and storage. We analyzed annual growth rings in the secondary xylem and measured stem anatomical traits in individuals from 18 populations of Plantago lanceolata growing in a 12‐year old grassland biodiversity experiment (Jena Experiment). Plant individuals of P. lanceolata were on average older and reproduced later with increasing species richness. Individuals of P. lanceolata were slightly younger and the age distribution within populations skewed to younger individuals in the presence of grasses. The presence of legumes did not affect mean age, but led to a more even age distribution within populations. The width of growth‐related tissues (xylem, phloem, phellem) decreased with increasing species richness. Plant diversity‐effects on storage‐related tissues (pith, cortex) were less consistent, as pith showed increasing width with species richness, while cortex did not change with plant diversity. Our results imply that plant diversity effects on population age structure and the expression of stem anatomical traits of P. lanceolata reflect a tradeoff: growth and turnover is fast at low diversity (younger age, higher allocation to growth‐related tissue, faster generative reproduction), while it is slow at high diversity (older age, higher allocation to storage‐related tissue, later generative reproduction).

Xylem anatomical and growth responses of the dwarf shrub Vaccinium myrtillus to experimental CO2 enrichment and soil warming at treeline

Plant growth responses to environmental changes may be linked to xylem anatomical adjustments. The study of such links is essential for improving our understanding of plant functioning under global change. We investigated the xylem anatomy and above-ground growth of the dwarf shrub Vaccinium myrtillus in the understorey of Larix decidua and Pinus uncinata at the Swiss treeline after 9 years of free-air CO2 enrichment (+200 ppm) and 6 years of soil warming (+4 °C). We aimed to determine the responses of xylem anatomical traits and growth to these treatments, and to analyse xylem anatomy–growth relationships. We quantified anatomical characteristics of vessels and ray parenchyma and measured xylem ring width (RW), above-ground biomass and shoot elongation as growth parameters. Our results showed strong positive correlations between theoretical hydraulic conductivity (Kh) and shoot increment length or total biomass across all treatments. However, while soil warming stimulated shoot elongation and RW, it reduced vessel size (Dh) by 14%. Elevated CO2 had smaller effects than soil warming: it increased Dh (5%) in the last experimental years and only influenced growth by increasing basal stem size. The abundance of ray parenchyma, representing storage capacity, did not change under any treatment. Our results demonstrate a link between growth and stem Kh in V. myrtillus, but its growth responses to warming were not explained by the observed xylem anatomical changes. Smaller Dh under warming may increase resistance to freezing events frequently occurring at treeline and suggests that hydraulic efficiency is not limiting for V. myrtillus growing on moist soils at treeline. Our findings suggest that future higher atmospheric CO2 concentrations will have smaller effects on V. myrtillus growth and functioning than rising temperatures at high elevations; further, growth stimulation of this species under future warmer conditions may not be synchronized with xylem adjustments favouring hydraulic efficiency.

Changes in structure and physiological functioning due to experimentally enhanced precipitation seasonality in a widespread shrub species

Semi-arid shrub steppe occupies a vast geographic range that is characterized in part by distinct seasonal patterns in precipitation. Few studies have evaluated how variability in both the amount and timing of precipitation affect the structure and physiology of shrubs in these systems. We quantified changes in foliar crown parameters, xylem anatomy, gas exchange, and hydraulic transport capacity in deep-rooted Artemisia tridentata shrubs following 20 years of experimental manipulations in amount and seasonal timing of precipitation. We hypothesized that shrub growth (total leaf area per shrub and cover of shrub community), hydraulic transport efficiency, and gas exchange would increase in shrubs in irrigated plots compared to non-irrigated control plots, especially for irrigation applied in winter rather than summer. We also predicted similar changes in xylem anatomy (ring width, vessel size and frequency). Most treatment responses entailed changes in plant structure, and were generally consistent with our hypotheses: total-shrub leaf area, shrub basal area, canopy cover, and maximum sapwood-specific branch hydraulic conductivity were more than 2× greater in shrubs in winter-irrigated compared to control plots, while summer irrigation had few effects on these variables. Irrigation in either season did not affect xylem vessel size, but did increase xylem ring width by ~ 2 × and decreased xylem vessel frequency by about half. Anatomical, morphological, and stand-level abundance of A. tridentata appeared much more responsive to irrigation than state changes in gas exchange, particularly when the extra water is received during winter. Thus, it appears for sagebrush that seasonal timing is at least as important as the amount of precipitation, and that responses to changes in precipitation timing occur through changes in carbon allocation more so than changes in leaf-level carbon gain.

Growth rings in roots of medicinal perennial dicotyledonous herbs from temperate and subtropical zones in China.

Growth years are closely related to the quality of Chinese medicinal materials, and they can provide a reliable basis for quality evaluation on crude drugs in accordance with the suitable growth years. Herbchronology, the numerical and pattern analysis of annual growth rings in herbaceous perennials, has emerged to be a recognized science that is applied in age determination of perennial forbs. Fifty medicinal species growing in temperate and subtropical zones of China were examined by microstructure observation to determine the presence of growth rings in the secondary root xylem of medicinal perennial dicotyledonous herbs. Nearly half of the surveyed species showed clearly or relatively clearly demarcated growth rings in their roots, and additional anatomical patterns have been observed in different species. Clear variations in growth rings of different genus or species were characterized in this study, and these findings proved the feasibility of applying herbaceous plant growth rings in age identification of traditional Chinese medicine.

Precipitation is not limiting for xylem formation dynamics and vessel development in European beech from two temperate forest sites.

We investigated the dynamics of xylem differentiation processes and vessel characteristics in Fagus sylvatica L. to evaluate the plasticity of xylem structures under different environmental conditions. In 2008-10, analyses were performed on microcores collected weekly from two temperate sites: Menina planina (1200 m above sea level (a.s.l.)) and Panska reka (400 m a.s.l.). The duration between the onset and end of major cell differentiation steps and vessel characteristics (i.e., density, VD; mean diameter, MVD; mean area, MVA; and theoretic conductivity area, TCA) were analysed in the first and last quarters of the xylem rings, also in respect of local weather conditions (precipitation, temperature). Although the onset, duration and end of xylem formation phases differed between the two sites, the time spans between the successive wood formation phases were similar. Significant differences in MVD, MVA and TCA values were found between the first and last quarters of xylem increment, regardless of the site and year. Vessel density, on the other hand, depended on xylem-ring width and differed significantly between the sites, being about 30% higher at the high elevation site, in beech trees with 54% narrower xylem rings. Vessel density in the first quarter of the xylem ring showed a positive correlation with the onset of cell expansion, whereas a negative correlation of VD with the cessation of cell production was found in the last quarter of xylem increment. This may be explained by year-to-year differences in the timing of cambial reactivation and leaf development, which effect hormonal regulation of radial growth. No significant linkage between intra-annual weather conditions and conduit characteristics was found. It can thus be presumed that precipitation is not a limiting factor for xylem growth and cell differentiation in beech at the two temperate study sites and sites across Europe with similar weather conditions.

Intra-annual leaf phenology, radial growth and structure of xylem and phloem in different tree parts of Quercus pubescens

Basic knowledge of the intra-annual timings of leaf development and radial growth (including the phloem part) in different tree parts is generally missing although such rudimentary data are crucial to link the structure and function of vascular tissues at the whole tree level. To understand better the time course of leaf development and radial growth patterns in different tree parts, we studied leaf phenology and intra-annual xylem and phloem formation and structure in the stem and at two locations in branches of sub-Mediterranean Quercus pubescens in 2015. Onset and end dates of cambial cell production were synchronized at the two locations in branches, but were different at the stem base. The period of cell production was thus a month longer in the stem, resulting in 82.8 and 45.1% wider xylem and phloem increments, respectively. In addition, the xylem ring was wider than the phloem ring in all three parts. Thus, phloem ring widths in stem represented 24.8% and in branches 79.4% of the xylem ring width. Earlywood occupied 52.9% (stem) and 74.9% (branches) of the xylem ring, and early phloem 53.7% (stem) and 43.3% (branches) of the phloem ring. Most of the annual radial increment (i.e. xylem and phloem increments) in stem and branches was formed prior to full leaf development. Latewood and late phloem were formed in the period of full leaf unfolding. Our study confirmed that the temporal sequence of leaf development and radial growth are not contemporary in Q. pubescens. Different intra-annual patterns of radial growth in different tree parts result in different structures of xylem and phloem, which is in line with different roles of stem and branches in terms of tree functioning.

ДОСЛІДЖЕННЯ АНАТОМІЧНОЇ БУДОВИ ПІДЗЕМНИХ ОРГАНІВ РОДОВИКА ЛІКАРСЬКОГО (SANGUISORBA OFFICINALIS L. )

Мета роботи. Родовик лікарський (Sanguisorba о№ сіпаіів L.) - багаторічна трав’яниста рослина, підземні органи якої здавна використовують у медицині як в'яжучий і кровоспинний засіб. Офіційною медициною використовуються препарати родовика лікарського з кореневища з коренями. У наукових джерелах недостатньо інформації про фармакогностичне вивчення підземних органів родовика лікарського, тому метою нашої роботи було вивчити анатомічну будову, встановити і зіставити діагностичні ознаки кореневищ і коренів, зібраних восени на першому і другому роках вегетації даного виду.Матеріали і методи. Виготовлення мікропрепаратів проводили за загальноприйнятими методами. Використовували мікроскоп МС 10 (окуляри Х5, Х10, 15, об’єктиви Х10, Х40). Мікрофотографії зроблені фотокамерою Sаmsung PL50.Результати й обговорення. Кореневище. Підземна частина родовика лікарського представлена багаторічним епігеогенним кореневищем з придатковими коренями. Кореневище поступово дерев’яніє, стає пухким, порожнистим у центрі. Анатомічна будова кореневища безпучкова. Молоді однорічні кореневища вкриті темно-бурим, поздовжньо зморшкуватим корком. У особин другого року вегетації клітини корка ущільнюються, починають злущуватись. Первинна кора однорічних кореневищ представлена шарами крупноклітинної паренхіми. Ксилема і флоема паренхіматизовані, пронизані розширеними радіальними серцевинними променями. В клітинах накопичуються прості і складні крохмальні зерна, часто зустрічаються друзи. Помітно виділяється щільне кільце камбію. Провідна система представлена судинами. Механічні волокна розташовані відокремлено, невеликими ділянками поблизу судин або утворюють суцільне кільце поряд з камбієм. Серцевина з міжклітинниками, паренхімні клітини з крохмальними зернами і друзами кальцій оксалату. Корені мають вторинну будову. Корок шаруватий, кільця з коричневим або жовтуватим вмістом чергуються з кільцями світлішими або безбарвними. Зона камбію багатошарова, темніша, добре помітна. Ксилема промениста. Трахеїди пористі. Серцевинних променів багато. У клітинах наявні дрібні прості овальні та округлі крохмальні зерна, друзи та поодинокі призматичні або багатогранні кристали кальцію оксалату. У дворічних коренів зовнішній шар корка товстий, темно-коричневий, з тріщинами; чітко виділяються річні кільця ксилеми, серцевинних променів багато, волокна лубу чисельні, здерев’янілі.Висновки. Досліджено анатомічну будову підземних органів родовика лікарського, зібраних на першому і другому роках вегетації. Виявлено мікроскопічні діагностичні ознаки кореневищ і коренів.

Cover Caption: Special issue: Plant vascular biology (2)

The cover shows secondary vascular bundles, produced by a unique monocot cambium, in which the phloem is centrally‐located, surrounded by a xylem ring (Zinkgraf et al., 436–449). In this issue, first insights into the genetic regulation and evolution of this fascinating meristem are presented in support of the hypothesis that genes regulating this vascular cambia were coopted in the evolution of this novel meristem that is found within some species of the Asparagales.