Alcuni Aspetti Della Variabilità Del Legno Secondario Di Un Esemplare Di Prunus Persica Stokes

Abstract

Some aspects of the variability in wood structure of a specimen of PRUNUS PERSICA Stokes. — The secondary xylem of a young stem of Prunus persica Stokes has been investigated under three main headings: 1) vessel and fibre length; 2) intrusive fibre growth; 3) relative amount of libriform fibres, fibretracheids and tracheids.

Vessel members and fibres have been reckoned from single rings and from the whole wood body.

The relation between the above mentioned dimensions and the position within the wood body and the width of the growth layers has been calculated.

No remarkable variation has been found along the axis of the stem; on the contrary there is a decrease in both fibres and vessels length along the radius of the stem from inside outwards. Such behaviour having never been recorded before, the possible causes are suggested.

A positive correlation has been found between the width of the growth layers and 1) vessel members and fibres length, 2) fibre intrusive growth, 3) percentage of libriform fibres. In addition a relative correlation between percentage of libriform fibres and age of the cambium has been put in evidence.     

Stem anatomy of Caryophyllaceae

The xylem and phloem of 88 Caryophyllaceae from subtropical and temperate regions mainly in Western Europe and the Canary Islands are described and analysed. They are compared with their taxonomic classification, and assigned to their ecological range. The xylem of different life forms (herbaceous plants, dwarf shrubs and shrubs) consists mainly of parenchyma and small vessels that are 20–50 μm in diameter in earlywood. They have simple perforations and pits are pseudosclariform and scalariform. The axial parenchyma is mostly pervasive or paratracheal, and the ray cells are exclusively upright or square. The anatomy of the subfamily Alsinoideae is homogeneous and characterised by the absence of libriform fibres, large rays, crystal druses and sclereids in the cortex. The subfamily Caryophylloideae is less homogeneous and mainly characterised by the presence of crystal druses on the xylem and phloem, as well as the presence of intra-annual fibre bands. The subfamily Paronychioideae is heterogeneous; included phloem is most characteristic. Ecological trends are clearly expressed by the age of plants and the average annual radial growth rates. Plants tend to grow older and slower at higher altitudes. The presence of intra-annual fibre bands in the xylem is characteristic of Caryophylloideae at lower altitudes. The study suggests that taxonomic and ecological classifications and large-scale ecological trend studies must be based on large and homogeneous datasets and well-defined anatomical features.     

Anatomy and Morphology of Pinnatiramosus,a New Plant from the Middle Silurian (Wenlockian) of China

A new genus and species Pinnatiramosus qianensis is described from the Xiushan Formation of Middle Silurian (Wenlockian)in the north of Guizhou, China. This plant consists of a prostrate axis and erect pinnate branching system. Conductin gbundle is comprised of tubular cells with scalariform or alternate simple pits. Pinnatiramosus gen. nov. Diagnosis: Plant cylindrical, differentiated into erect branches and prostrate axes; erect branches much branched, consisting of regular or irregular pinnate lateral branches; laterals opposite or alternate, with basal parts constricted and acute or blunt apices. Conducting bundle comprised of longitudinally aligned tubes with secondary thickening. Reproductive structures nor seen. Derivation of name: Pinnatus (Latin)=pinnate and ramosus (Latin)=ramose, referred to the external morphology of the plant. Pinnatiramosus qianensis sp. nov. Diagnosis: Characters described as the genus. Prostrate axes at least 400 mm in length and 3–6 mm in diameter, produced erect longer branches and downward shorter branches; erect branches up to 200 mm long and vary from 1.0 to 2.5mm in diameter, branched at least six orders, with lateral branches unequally developed, long laterals scattered among short ones; lateral branches oppositely or alternately arranged on main axis, 1–3 mm: apart; ultimate bran- ches 0.4–0.8 mm in diameter, with acute or blunt apex; borne at angles of 40–70˚ with main axis. Conducting bundle ca. 1/4 of the axis diameter, composed of tubular elements with secondary thickening; tubes range from 15–54μm in diameter, with blunt end wall; secondary wall averages 4.86 μm in thickness, ranging 2.5–6.6 μm, with scalariform and alternate pits. Derivation of name: Qian is the abbreviation for Guizhou province from where the plants are found. In this paper, is made the comparison of this new plant with fossil and living algae as well as early vascular plants on the basis of its external morphology and internal structure According to the comparison, Pinnatiramosus belongs to one of specialized plants with tracheophyte- like conducting tissue. Some interesting opinions are here provided as follows: (i) Silurian is, an important age of plant evolution. During this period certainly coexist not only various algae and undoubted vascular plants but also a group of interesting plants that were just immigrating from aquatic to terrestrial environments. (ii) The transmigration of algae from water to land occurred along several different evolutionary lines. Accompanying changes of these algae on morphology and anatomy were adapted to terrestrial environments. (iii) Pinnatiramosus represents a group of new plants with remarkably nontracheophyte morphology but tracheophyte- like anatomy. (iv) The tracheid-like tubes, macerated out of Silurian rocks, derived more probably from non-vascular plants such as Pinnatiramosus, Prototaxitesor Nematothallus than from vascular plants.     

不同生境下蓝桉的木材解剖研究

用光镜及扫描电镜对不同生境下的蓝桉（Ｅｕｃａｌｙｐｔｕｓｇｌｏｂｕｌｕｓ Ｌａｂｉｌｌ．）木材结构进行了解剖学观察,描述了木材结构特征。以蓝桉木材的１１ 个主要特征——导管频率、单孔率、导管直径、导管分子长度、管胞长度和直径、纤维管胞长度和直径、纤维长度、射线频率和高度为指标,对生长在不同生境下的蓝桉进行比较发现：随着纬度的增加,生长轮变化不明显;木材中大部分组成分子的数量特征,除导管频率有降低趋势外均与纬度成正相关。评述了年降雨量对蓝桉木材结构的影响     

Studies on Wood Anatomy of Eucalyptus globulus Under Different Habitats

Wood anatomy of Eucalyptus globulus Labill. under different habitats was comparatively studied under light and scanning electron microscope. According to the eleven major quantitative perimeters of wood characteristics of E. globulus viz: vessel frequency, percentage of solitary vessels, vessel diameter, vessel member length; tracheid length and diameter; fibre tracheid length and diameter; libriform fibre length; ray frequency and ray height, the plants under different habitats have been made a comparison. The results showed that growth ring was indistinct, and there was a positive correlation between the quantitative characters of most wood constituent members were positively correlated with the latitude except for some of vessel frequency decreased. The decrease in effects of annual rainfall on the structure of the wood of E. glotrulus were evaluated.     

Influence of Bud Position and Plant Ontogeny on the Morphology of Branch Shoots in Pea (Pisum sativum L. cv. Alaska)

The morphology of axillary shoots of pea plants (Pisum sativumL. cv. Alaska) was analysed as a function of the position ofthe bud on the plant axis and the stage of plant developmentwhen the buds began to grow. Buds from the three most basalnodes were stimulated to develop by decapitating the main shootwhen buds were still growing (4 d plants), shortly after budsbecame dormant (7 d plants) or after the initiation of floweringon the main shoot (post-flowering plants, about 21 d after sowing).Branch shoots were scored for node of floral initiation (NFI),shoot length, and node of multiple leaflets (NML), a measureof leaf complexity. Shoots that developed spontaneously fromupper nodes (nodes 5-9) on intact post-flowering plants werescored for NFI. NFI for basal buds on 4 and 7 d plants variedas a function of nodal position and ranged from 5 to 6·7nodes. NFI on these plants was not influenced by bud size orwhether a bud was growing or dormant when the plant was decapitated.NFI for shoots derived from basal buds on decapitated post-floweringplants and upper nodes on intact post-flowering plants was about4. Reduced NFI on post-flowering plants may be due to depletionof a cotyledon-derived floral inhibitor. Basal axillary shootson 4 d plants were about 20% longer than those on 7 d plantsand about five times longer than those on post-flowering plants.These differences may be due to depletion of gibberellic acidsfrom the cotyledons. NFI and NML for the main shoot and forbasal axillary shoots were similar under some experimental conditionsbut different under other conditions, so it is likely that eachdevelopmental transition is regulated independently.Copyright1995, 1999 Academic Press Apical dominance, bud development, garden pea, initiation of flowering, Pisum sativum L., shoot morphology     

The Initiation and Development of Secondary Xylem in Axillary Branches of Populus deltoides

The initiation of secondary xylem in elongating axillary branchesof Populus deltoides Bartr. ex Marsh. is independent of thatin the main stem. Although secondary xylem differentiates acropetallyin the main stem, it does not differentiate from the stem intothe axillary branch. Secondary xylem is usually initiated ininternode 4 (occasionally 3) of the axillary branch, and fromthis site it develops both acropetally in the elongating branchand basipetally toward the main stem. Secondary vessel differentiationalways precedes fibre differentiation. Although secondary xylemdifferentiates in internodes that have ceased elongation, itdifferentiates first in traces of the vascular cylinder servingrapidly expanding and maturing foliage leaves. As younger leaveson the branch expand and mature, secondary xylem differentiatesin their traces eventually producing a complete secondary vascularcylinder. Scale leaves do not initiate secondary xylem independentlyin their traces; they are activated by adjacent traces in thevascular cylinder serving foliage leaves. Once established,the primary-secondary vascular transition zone advances acropetallyin a branch just as it does in the main stem. Populus deltoides Bartr. ex Marsh., cottonwood, axillary branches, secondary xylem, plastochron index, post-dormancy development, xylem.     

都支杜鹃茎、叶解剖特征与环境的适应性

利用光学显微解剖技术,对生长于大别山区的都支杜鹃（Rhododendron shanii Fang)的茎、叶进行了解剖学与环境适应性之间的关系研究。结果表明：叶的上表皮具有厚的角质膜、复表皮、气孔缺失;下表皮被毛,气孔分布密集,气孔突出;叶肉中栅栏组织和纤维丰富,且纤维呈束存在,并形成了叶肉中的支撑系统,海绵组织内具有发达的通气组织;茎中木栓宽广,次生韧皮部与次生木质部厚度比是1/5,次生木质部中管孔直径狭窄、管密孔集,绝大多数为管胞,同时木纤维十分丰富。上述结构的特异性均表明茎和叶在诸多方面表现为结构与环境的统一性,是特殊综合生态环境长期作用的结果。复表皮、主脉周韧维管束、次生木质部缺少导管等这些特征均说明都支杜鹃在系统分类中应处于较原始的地位。     

The dynamic pipeline: hydraulic capacitance and xylem hydraulic safety in four tall conifer species

Recent work has suggested that plants differ in their relative reliance on structural avoidance of embolism versus maintenance of the xylem water column through dynamic traits such as capacitance, but we still know little about how and why species differ along this continuum. It is even less clear how or if different parts of a plant vary along this spectrum. Here we examined how traits such as hydraulic conductivity or conductance, xylem vulnerability curves, and capacitance differ in trunks, large‐ and small‐diameter branches, and foliated shoots of four species of co‐occurring conifers. We found striking similarities among species in most traits, but large differences among plant parts. Vulnerability to embolism was high in shoots, low in small‐ and large‐diameter branches, and high again in the trunks. Safety margins, defined as the pressure causing 50% loss of hydraulic conductivity or conductance minus the midday water potential, were large in small‐diameter branches, small in trunks and negative in shoots. Sapwood capacitance increased with stem diameter, and was correlated with stem vulnerability, wood density and latewood proportion. Capacitive release of water is a dynamic aspect of plant hydraulics that is integral to maintenance of long‐distance water transport.     

The spatial pattern of air seeding thresholds in mature sugar maple trees

Air seeding threshold (P_a) of xylem vessels from current year growth rings were measured along the vertical axis of mature sugar maple trees (Acer saccharum Marsh.), with sampling points in primary leaf veins, petioles, 1-, 3-, and 7-year-old branches, large branches, the trunk and roots. The air seeding threshold was taken as the pressure required to force nitrogen gas through intervessel pit membranes. Although all measurements were made on wood produced in the same year, P_a varied between different regions of A. saccharum, with distal organs such as leaves and petioles having lower P_a than basal regions. Mean (SE) P_a ranged from 1.0 (± 0.1) MPa in primary leaf veins to 4.8 (± 0.1) MPa in the main trunk. Roots exhibited a P_a of 2.8 (± 0.2) MPa, lower than all other regions of the tree except leaf veins and petioles. Mean xylem vessel diameter increased basipetally, with the widest vessels occurring in the trunk and roots. Within the shoot, wider vessels had greater air seeding thresholds, contrasting with trends previously reported. However, further experimentation revealed that differences in P_a between regions of the stem were driven by the presence of primary xylem conduits, rather than differences in vessel diameter. In 1-year-old branches, P_a was significantly lower in primary xylem vessels than in adjacent secondary xylem vessels. This explained the lower values of P_a measured in petioles and leaf veins, which possessed a greater ratio of primary xylem to secondary xylem than other regions. The difference in P_a between primary and secondary xylem was attributed to the greater area of primary cell wall (pit membrane) exposed in primary xylem conduits with helical or annular thickening.     

A WOODY LYCOPSID STEM FROM THE NEW ALBANY SHALE (LOWER MISSISSIPPIAN) OF KENTUCKY

A lycopsid axis from the New Albany Shale (Sanderson Formation) of Kentucky is described. The stem, which branches dichotomously, is 45 mm in diameter and is characterized by a relatively narrow parenchymatized protostele, a 3.0 mm-thick cylinder of secondary xylem, a tripartite cortex, and a periderm that is more than 5.0 mm thick. The secondary xylem is composed of uniseriate and biseriate vascular rays and narrow tracheids with scalariform wall thickenings on both radial and tangential walls. The periderm is characterized by elongate, thick-walled cells, some of which broaden tangentially in the outer part of the tissue forming zones that appear wedge-shaped in cross section. Surface features of the axis, including leaf bases, are not preserved. The stem is tentatively regarded as a member of the Lepidodendrales in accordance with the numerous anatomical characters that it shares with more recent representatives of the order. Because the external morphology is not known, however, the possibility exists that the axis corresponds to a protolepidodendralean taxon currently known only from compression and/or impression remains or some other nonlepidodendralean plant that produced secondary xylem. The extremely narrow profile of the secondary xylem tracheids (relative to other arborescent lycopsids) is interpreted as evidence that the plants grew in a habitat that was substantially drier than the Upper Carboniferous coal swamps.     

Structural Study of Secondary Xylem in Bretschneidera sinensis Hemsl.

The anatomical structure of the wood of Bretschneidera sinensis Hemsl. was studied with both light and scanning electron microscopy. The main characters of the secondary xylem are as follows: (1) The wood is diffuse porous with distinct growth ring. (2) Most vessel elements possess simple perforation plates, only a few are with scalariform perforation plates, but both of them have spiral thickenings on their secondary walls. (3) Tracheids, fiber-tracheids and libriform fibers all exist and the libriform fibers may or may not have septa. (4) Wood parenchyma is mainly of terminal distribution type. (5) Wood ray is heterogenous belonging to the Krib′s heterogenous IIB type. (6) Tylosis, resin canal and secretory cell are absent. Based on the present study and other data derived from external morphology, bark anatomy, chromosome study, palynology and embryogenetic study, the systematic position of Bretschneidera sinensis was analysed and discussed. The authors agree that the genus should be elevated to the level of a monotypic family—Bretschneideraceae, belonging to the order of Sapindales; also it is closely related to other primitive families of the same order such as Staphyleaceae, Sabiaceae and Connaraceae.     

丛枝菌根真菌对杨树生长、气孔和木质部微观结构的影响

植物气孔与木质部导管及纤维的功能直接关系着植物的水分利用, 进而影响植物的生长。为研究丛枝菌根真菌(AMF)对杨树抗旱性的影响, 采用温室盆栽的方法, 研究两种水分条件下, 接种根内球囊霉(Rhizophagus irregularis)对速生杨107 Populus × canadensis (P. nigra × P. deltoides) ‘Neva’气孔及木质部微观结构的影响。结果表明: AMF的侵染显著提高了杨树幼苗地上和地下部分生物量, 对叶片气孔长度、茎部导管细胞直径和纤维细胞长度也有促进作用。AMF对生物量和导管细胞直径的增加幅度表现出干旱条件下>正常水分条件下, 而对气孔长度的提高幅度表现出干旱条件下<正常水分条件下。正常水分条件下, AMF增加了杨树叶片的气孔密度, 减小了纤维细胞直径, 对相对水分饱和亏缺无影响; 干旱条件下, AMF增加了纤维细胞直径, 降低了相对水分饱和亏缺, 对气孔密度无影响。综上所述, 干旱条件下, AMF对导管水分传输能力的促进作用明显增加, 而对气孔蒸腾能力的促进作用有所减少, 从而更利于杨树在遭遇干旱时保持水分, 减少干旱对菌根杨树造成的水分亏缺, 提高菌根杨树对干旱的耐受性。     

Drought-Induced Xylem Dysfunction in Petioles,Branches, and Roots of Populus balsamifera L. and Alnus glutinosa (L.) Gaertn

Variation in vulnerability to xylem cavitation was measured within individual organs of Populus balsamifera L. and Alnus glutinosa (L.) Gaertn. Cavitation was quantified by three different techniques: (a) measuring acoustic emissions, (b) measuring loss of hydraulic conductance while air-dehydrating a branch, and (c) measuring loss of hydraulic conductance as a function of positive air pressure injected into the xylem. All of these techniques gave similar results. In Populus, petioles were more resistant than branches, and branches were more resistant than roots. This corresponded to the pattern of vessel width: maximum vessel diameter in 1- to 2-year-old roots was 140 [mu]m, compared to 65 and 45 [mu]m in rapidly growing 1-year-old shoots and petioles, respectively. Cavitation in Populus petioles started at a threshold water potential of -1.1 MPa. The lowest leaf water potential observed was -0.9 MPa. In Alnus, there was no relationship between vessel diameter and the cavitation response of a plant organ. Although conduits were narrower in petioles than in branches, petioles were more vulnerable to cavitation. Cavitation in petioles was detected when water potential fell below -1.2 MPa. This value equaled midday leaf water potential in late June. As in Populus, roots were the most vulnerable organ. The significance of different cavitation thresholds in individual plant organs is discussed.     

Distribution of vessel size,vessel density and xylem conducting efficiency within a crown of silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis>)

Spatial patterns in vessel diameter, vessel density and xylem conducting efficiency within a crown were examined in closed-canopy trees of silver birch (Betula pendula). The variation in anatomical and hydraulic characteristics of branches was considered from three perspectives: vertically within a crown (lower, middle and upper crown), radially along main branches (proximal, middle and distal part), and with respect to branch orders (first-, second- and third-order branches). Hydraulically weighted mean diameter of vessels (D _h) and theoretical specific conductivity of the xylem (k _t) exhibited no vertical trend within the tree crown, whereas leaf-specific conductivity of the xylem (LSC_t) decreased acropetally. Variation in LSC_t was governed by sapwood area to leaf area ratio (Huber value) rather than by changes in xylem anatomy. The acropetal increase in soil-to-leaf conductance (G _T) within the birch canopy is attributable to longer path length within the lower-crown branches and higher hydraulic resistance of the shade leaves. D _h, k _t and LSC_t decreased, while vessel density (VD) and relative area of vessel lumina (VA) increased distally along main branches. A strong negative relationship between vessel diameter and VD implies a trade-off between hydraulic efficiency and mechanical stability of xylem. D _h and VD combined explained 85.4% of the total variation of k _t in the regression model applied to the whole data set. Xylem in fast-growing branches (primary branches) had greater area of vessel lumina per unit cross-sectional area of sapwood, resulting in a positive relationship between branch radial growth rate and k _t. D _h, k _t and LSC_t decreased, whereas VD increased with increasing branch order. This pattern promotes the hydraulic dominance of primary branches over the secondary branches and their dominance over tertiary branches. In this way crown architecture contributes to preferential water flow along the main axes, potentially providing better water supply for the branch apical bud and foliage located in the outer, better-insolated part of the crown.     

Fibres and Fibre-sclereids in Wild-typeArabidopsis thaliana

Examination of the fibre system in roots and shoots ofArabidopsisthaliana(L.) Heynh. revealed three types of fibres, distinguishedaccording to their site of differentiation: (1) short fibre-sclereidsin the secondary phloem of roots and shoots at the rosette level;(2) long fibres in the secondary xylem of the main root; and(3) very long fibres in the xylem of the inflorescence stems.These three types are in addition to the small number of primaryphloem fibres that are formed even in smallA. thalianaindividuals.These findings provide a basis for the use ofArabidopsis thalianaasa model system to study the processes leading to fibre differentiationin dicotyledons. Arabidopsis thaliana; differentiation; fibre-sclereids; inflorescences; phloem fibres; xylem     

杨树新梢积累营养贮藏蛋白质的细胞学研究

采用光学显微镜和电子显微镜技术,对杨树新梢中的营养贮藏蛋白质进行了细胞学鉴定。在用戊二醛固定的标本中,营养贮藏蛋白质呈颗粒状,积累在中央大液泡里。在新梢伸长生长时期,新梢茎的基部已积累了营养贮藏蛋白质,在伸长生长刚停止,中上部的叶片近成熟时,整个新梢的茎都有营养贮藏蛋白质的积累,其中,以新梢基部的茎最为丰富。营养贮藏蛋白质优先在次生韧皮部的韧皮薄壁细胞和韧皮射线薄壁细胞中积累,在新梢伸长生长停止后,新梢基部茎的木质部中也积累了相当数量的营养贮藏蛋白质,主要分布在初生木质部和内侧次生木质部的各种生活的薄壁细胞中。新梢较早地积累营养贮藏蛋白质是热带树木和温带树木的一个共同特点,对于树木的氮代谢和树木当年的生长发育可能具有重要的调控作用。     

Wood and stem anatomy of woody Amaranthaceae s.s.: ecology, systematics and the problems of defining rays in dicotyledons

Wood and stem anatomy is studied for seven species of six genera (root anatomy also reported for one species) of Amaranthaceae s.s. Quantitative data on vessels correlate closely with relative xeromorphy of respective species, agreeing with values reported for dicotyledons without successive cambia in comparable habitats. Libriform fibre abundance increases and vessel diameter decreases as stems and roots of the annual Amaranthus caudatus mature. Long, thick-walled fibres in Bosea yervamora may be related to the upright nature of elongate semi-climbing stems. Non-bordered or minutely bordered perforation plates characterize Amaranthaceae, as they do most other Caryophyllales. Amaranthaceae have idioblastic cells containing druses, rhomboidal crystals or crystal sand: these forms intergrade and seem closely related. Rays are present in secondary xylem of the Amaranthaceae studied. Cells intermediate between ray cells and libriform fibres occur in Charpentiera elliptica . Degrees of diversity in rays and reports of raylessness in Amaranthaceae induce discussion of definition and identification of rays in dicotyledons; some sources recognize both rays and radial plates of conjunctive tissue in Amaranthaceae. The action of successive cambia is described: lateral meristem periclinal divisions produce secondary cortex externally, conjunctive tissue internally and yield vascular cambia as well. Vascular cambia produce secondary phloem and secondary xylem, in both ray and fascicular zones, as in a dicotyledon with a single cambium. Identification of meristem activity and appreciation of varied ray manifestations are essential in understanding the ontogeny of stems in Amaranthaceae (which have recently been united with Chenopodiaceae).  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 1–19.     

三种植物生长物质对大豆叶茎解剖结构的影响

在大田栽培条件下,大豆‘垦农4号’于开花始期叶面喷施植物生长物质2-N,N-二乙氨基乙基己酸酯（DTA）、氯化胆碱（CC）和SOD模拟物（SODM）,并比较不同植物生长物质影响大豆叶片、叶柄和茎的解剖结构。结果表明,喷施植物生长物质后30d,叶中栅栏组织厚度及栅海比均增加;喷施SODM、DTA的叶中主脉维管束横截面积和木质部导管数目增加,CC对主脉维管柬横截面积和木质部导管数目的影响不明显;喷施3种植物生长物质的叶柄表皮细胞厚度、叶柄维管束横截面积和导管数量增加,茎部薄壁组织、韧皮部和木质部厚度增加,茎的直径也增加。