The Position of Cambia Regenerating in Grafts between Stems and Abnormally-oriented Petioles

When petioles are grafted to stems, vascular cambia regeneratein the callus that proliferates between the opposed cut surfaces.Three different patterns of cambial distribution are shown toarise in three types of graft union between stems and dorsiventralpetioles grafted in certain abnormal orientations. Simulations demonstrate that these patterns, as well as thosefound in two types of graft with normally oriented petioles,can be accounted for in terms of the gradient induction hypothesis,which states that the position and orientation of vascular cambiaare controlled by the ratio of concentrations of two diffusiblemorphogens. grafts, vascular cambium, regeneration, callus, morphogen, dorsiventrality, positional control     

Biomechanical Responses of Chamaedorea and Spathiphyllum Petioles to Tissue Dehydration

Data are presented for the mechanical responses to dehydrationof petioles from two monocotyledons (Chamaedorea erumpens andSpathiphyllum Clevelandii). These data were used to test thehypothesis that the mechanical properties (elastic modulus Eand flexural stiffness EI) of petioles from C. erumpens arealtered significantly less by dehydration than those of petiolesfrom Spathiphyllum. Dehydration, resulting from either dryingat room temperature or from submergence in various concentrationsof mannitol solutions, produced significant increases in E anddecreases in EI (due to geometric distortions) in both youngand mature Spathiphyllum petioles. Similar trends were observedfor young petioles of C. erumpens, but significantly less sofor mature petioles of this species. Regardless of petiolarage, E increased allometrically as a linear function of tissuedensity, which in turn correlated with the volume fraction oflignified tissues in petioles; however, the proportional increaseof E as a function of tissue density was significantly greaterfor C. erumpens petioles than for Spathiphyllum. Anatomicalanalyses of petiolar transections indicated that Chamaedoreapetioles had larger volume fractions of lignified tissues thanthose of Spathiphyllum and that these tissues were located tomaximize stiffness. These data (and previously reported allometricrelationships between EI and petiolar length) shed light onthe difficulties in evaluating the ‘costs’ of committingtissues to mechanical support. Petioles, biomechanics, leaf anatomy, monocotyledons     

Identification of the Excitable Cells in the Petiole of Mimosa pudica by Intracellular Injection of Procion Yellow

Excitable cells in the petiole of Mimosa pudica were locatedby microelectrode technique and stained with Procion YellowMx4R which was previously filled in the electrode and injectediontophoretically into the cells. Microscopic observations ofsections of the stained petioles revealed that protoxylem parenchymacells and narrow phloem cells were excitable. The protoxylemlocalized just inside the metaxylem was composed almost entirelyof the parenchyma cells which were 106.3±5.2 µmlong (mean±EM, n=15) and 14.2±0.6 µm indiameter (n =33). The excitable phloem cells were 76.4±4.1µm long (n=7) and 7.0±0.3 pan in diameter (n=37)and were thought to be companion cells or narrow parenchymacells or both. Amplitudes of action potentials recorded fromthe petiolar surface had a linear relation to those from theexcitable cells in the same petiole. From this fact and thearrangement of excitable cells in the petiole, we conclude thatwhen the transmission of action potential takes place in thepetiole all excitable cells in it are activated. ¹ Present address: 1st Department of Physiology, Hamamatsu UniversitySchool of Medicine, Handa-cho 3600, Hamamatsu 431-31, Japan. (Received September 7, 1982; Accepted November 8, 1982)     

Differences between Acer saccharum Leaves from Open and Wind-Protected Sites

Size-correlated variations of sugar maple (Acer saccharum L.)leaf anatomy and mechanical properties were determined for twosaplings (from open and wind protected sites) to examine theeffects of chronic wind-induced mechanical disturbance on leafsize, rigidity and flexibility. Based on a total sample of 78leaves, comparisons indicated that the mean size of the opensite leaves (n =37) was smaller in every measured respect comparedwith that of the closed site leaves (n =41). Open site leaveshad, on average, smaller lamina surface area, shorter and narrowerpetioles with a smaller volume fraction of lignified tissuesthan those from the closed site. Biomechanical comparisons alsoindicated that the petioles of open site leaves were significantlyless rigid and more flexible than the petioles of closed siteleaves. Despite differences in mean leaf size and petiolar rigidityand flexibility, allometric comparisons indicated the size-dependentvariations in leaf properties were continuous across the twosites. Also, the allocation of leaf biomass with respect tostem biomass along the lengths of the two saplings was statisticallyidentical and indistinguishable from an isometric relationship.However, the smaller diametered branches of the open site saplingbore smaller and fewer leaves with less stiff and rigid petiolesthan those of the closed site sapling. The differences betweenopen and closed site leaves are interpreted to be functionallyadaptive and to indicate that chronic mechanical disturbanceof developingAcer saccharum leaves prefigures mature leaf sizeand petiole properties that have the capacity to reduce winddrag. Results from petioles are contrasted with those of mechanicallydisturbed stems. Leaves; Acer saccharum ; biomechanics; wind-drag; allometry     

Photoassimilate translocation in the petiole of Cyclamen and Primula is independent of lateral retrieval

Phloem translocation of photoassimilates between source andsink is considered to be linked with active retrieval of sugarsleaked to the vascular apoplast. This hypothesis was evaluatedby studying photo-assimilate movement in petioles of intactplants of Cyclamen persicum and Primula obconica in the presenceof inhibitors affecting sucrose retrieval (PCMBS, CCCP). Inhibitorsolutions were applied by rinsing locally isolated petiole bundlesor by injection into the petioe parenchyma. PCMBS and CCCP reduced[¹⁴C]sucrose retrieval from the petiole apoplast by the vascularcells and altered the distribution pattern of ¹⁴C-photoassimilateswithin the petiole tissues. However, these treatments did notaffect translocation through the petiole phloem. Evidence isprovided that the reagents were present in the vascular apoplastsurrounding the translocating phloem. It was concluded thatassimilate movement in the petiole of Cyclamen and Primula wasindependent of apoplastic retrieval. Key words: Cyclamen, Primula, phloem, transport, path, sucrose, retrieval     

Changes in Soybean Raceme and Petiole Anatomy Induced by 6-Benzylaminopurine

An enlargement of the peduncle and rachis of the terminal racemeand the petiole of the uppermost mainstem leaf was observedin soybean plants [Glycine max (L.) Merr.] treated with thecytokinin, 6-benzylaminopurine (BAP). Histological studies wereperformed to determine the timing and extent of anatomical changesaccompanying BAP treatment. Swelling of treated ‘Tracy-M’peduncles, rachises, and petioles was observed within 4–6d after treatment initiation. A significant increase in totalcross-sectional tissue area was observed at lower and intermediateinternodes of treated rachises after 11 d. Rachis enlargementwas due to increases in both cell size and cell number, particularlyof the vascular tissue. In treated petioles of IX93-100, procambialcells of vascular bundles were the first to respond to the BAPtreatment. These cells differentiated into a vascular cambiumwhich formed secondary xylem and phloem. Soybean, Glycine max (L.) Merr., anatomy, rachis, BAP.     

Graft establishment between compatible and incompatible Prunus spp

Graft compatibility has been studied in apricot (prunus armeniacaL.) grafted on Prunus cerasifera Ehrh. Two apricot cultivars,one compatible and one incompatible on this rootstock, wereselected for this study. In these species incompatibility isonly manifested by tree breakdown at a late phase of the tree'slife. The process of graft union formation was observed forthe first month following grafting. No differences were foundeither in the process of healing or in its kinetics. Thus, callusproliferation, callus differentiation and vascular connectionsare established in the same way and at the same time in bothcompatible and incompatible grafts. However, clear differencesexist in the level of differentiation of the callus produced.While in compatible grafts, callus quickly differentiates intocambium and vascular tissue, in incompatible grafts this differentiationis not complete and a portion of the tissue evolves into a parenchymatoustissue that coexists with the differentiated vascular tissue. Key words: Graft, Prunus, compatibility     

Callus Formation and Differentiation at an Exposed Cambial Surface

The origin of callus from the exposed surface of the cambialzone in Trema orientalis Bl. and Julbernardia globiflora (Benth.)Troupin is described and discussed in relation to what has beenobserved in other species. It is suggested that in differentspecies callus may develop from any of the undifferentiatedcentripetal products of the vascular cambium, but that the kindof tissue contributing to callus initiation depends upon thespecies and on the histology of the cambial zone. The establishment of a new vascular cambium and phellogen isalso described. It is found that cambium formation is not dependenton the presence of a preexisting cambium in the surroundingtissues and that the first-formed xylem is abnormal in structure.     

The role of light and growth regulators in the opening of the dentaria petiolar hook

The phenomenon of the etiolated hook is not restricted to the hypocotyl of the dicotyledenous plant (e.g., Phaseolus) but appears to serve a similar, adaptive function in the petioles of certain rhizomatous plants. The commonly employed regulants of hypocotyl hook opening were tested for their effect on the petiolar hook of Dentaria diphylla. The hook was found to require both light (red light promoted, far red inhibited) and the intact leaf for opening. The leaf requirement was fully replaced by gibberellic acid (0.04% in lanolin) but only in light; cobalt chloride (0.1-1.0 mm) promoted a partial opening in dark with or without leaf; and coumarin (1 mm), indoleacetic acid (1-4% in lanolin), and ethylene 10 microliter per liter all inhibited opening of hooks with or without lamina. The absolute requirement for light and leaf tissue and the replacement of proximal tissue by GA₃ alone represent marked differences in the physiology of hypocotyl and petiolar hooks. These differences are believed to indicate the necessity for concomitant leaf maturation in petiolar hook opening.     

COMPARATIVE STUDIES OF THE NODAL AND VASCULAR ANATOMY IN THE NEOTROPICAL CYATHEACEAE. III. NODAL AND PETIOLE PATTERNS; SUMMARY AND CONCLUSIONS

Comparative studies of the nodal and vascular anatomy in the Cyatheaceae are discussed as they relate to the taxonomy and phylogeny of the family. There is in the Cyatheaceae (excluding Metaxya and Lophosoria) a basic nodal pattern consisting of four major phases of leaf trace separations. Abaxial traces arise from the leaf gap margins, and the last abaxial traces from each side of the gap are larger and undergo numerous divisions. Distally adaxial traces separate from the gap margins, and the last adaxial traces are usually larger and undergo multiple divisions. In addition, medullary bundles frequently become petiole strands of the adaxial arc in the petiole. Rarely, cortical bundles form petiole strands in the abaxial arc in the petiole. Leaf gaps of the squamate genera of the Cyatheaceae are fusiform and possess prominent lateral constrictions which result from medullary bundle fusions and the separation of leaf traces. A characteristic petiole pattern is found in all members of the Cyatheaceae. There is an increase in the complexity of the petiole vascular tissue which results in a gradation from the undivided strand in Metaxya, to the three-parted petiole pattern in Lophosoria, and finally to the much-dissected petiole vascular tissue in the advanced genera. Nodal and vascular anatomy data basically support Tryon's phyletic scheme for the family. The Sphaeropteris-Alsophila-Nephelea line shows certain tendencies toward increased complexity of nodal and vascular anatomy, whereas the Trichipteris-Cyathea-Cnemidaria line shows the same anatomical and morphological characters in a direction of increased simplification or reduction.     

Using decellularized grafted leaves as tissue engineering scaffolds for mammalian cells

Inadequate availability of organs and tissues for transplantation is a major problem. While offering an alternative, development of engineered tissue constructs containing a functional vascular network that allows delivery of nutrients and especially O₂ remains a challenge. Using native vasculature, especially microvasculature, of a tissue or an organ offers potential to overcome this shortcoming. Decellularized animal organs retain the extracellular matrix (ECM) scaffold and native vascular networks but are challenging to source. A low cost, more readily available, and consistent source of tissues and organs is required. We investigated a plant scaffold model that would mimic input (arterial)-output (venous) flow by grafting two Aptenia cordifolia leaves together with opposite facing petioles. The abaxial epidermis of the top leaf and the adaxial epidermis of the bottom leaf were removed; wounds were soaked for 20 s in 0.1-mg L⁻¹ naphthaleneacetic acid (NAA) and 1-mg L⁻¹ benzylaminopurine (BAP) before horizontally appressing the wounded side of each leaf together. Leaves were decellularized 2 to 4 wk after grafting, lyophilized, and stored at room temperature. Prior to use, grafts were sterilized by ethylene oxide and rehydrated. Structural connections between the leaves were visualized histologically in thin sections using hematoxylin and eosin (H&E) and toluidine blue stains. Ponceau Red dye and red blood cells were perfused into the grafted leaves through one petiole of one leaf after decellularization to observe flow from input petiole into the first and then the second of the grafted leaves prior to exiting via the output petiole. Grafts were recellularized with the green fluorescent protein (GFP) expressing human breast cancer line MDA-MB231 and cell attachment and morphology observed 7 d post cell seeding. Results suggest that these grafted leaves provided an input-output cell-compatible vascularized scaffold as a possible bioscaffold for engineering tissues for transplantation.

     

Histological responses of isolated leaves to hormones applied across a transverse gradient

The responses of petiolar tissue of isolated leaves of Argyreianervosa to hormones were investigated by maintaining a transversegradient of auxin and auxin antagonist or auxin and gibberellin.The auxin used was ß-indolylbutyric acid (IBA) andthe auxin antagonist applied was maleic hydrazide. Gibberellicacid was also applied simultaneously with IBA. The experimentwas designed in such a way that while the solution of one hormonewas applied internally to the petiole with a capillary tube,the external surface of the petiole came in contact with thesolution of the other hormone. Wounding was caused in the pith by inserting a capillary tube.The division of the parenchymatous cells bordering the woundwas greater and cell dimension was less when auxin was appliedinternally but cell division was restricted and cell dimensionincreased when the auxin antagonist was applied at high concentrations.Root primordia and vascular tissues were formed in the pithwhen the concentration of auxin in the vicinity was greater.But these processes were blocked when the concentration of theauxin antagonist was greater in the neighborhood. The effectof auxin and gibberellin was synergistic in inducing these processes. (Received May 23, 1980; )     

Histological responses of isolated leaves to hormones applied across a transverse gradient

The responses of petiolar tissue of isolated leaves of Argyreianervosa to hormones were investigated by maintaining a transversegradient of auxin and auxin antagonist or auxin and gibberellin.The auxin used was ß-indolylbutyric acid (IBA) andthe auxin antagonist applied was maleic hydrazide. Gibberellicacid was also applied simultaneously with IBA. The experimentwas designed in such a way that while the solution of one hormonewas applied internally to the petiole with a capillary tube,the external surface of the petiole came in contact with thesolution of the other hormone. Wounding was caused in the pith by inserting a capillary tube.The division of the parenchymatous cells bordering the woundwas greater and cell dimension was less when auxin was appliedinternally but cell division was restricted and cell dimensionincreased when the auxin antagonist was applied at high concentrations.Root primordia and vascular tissues were formed in the pithwhen the concentration of auxin in the vicinity was greater.But these processes were blocked when the concentration of theauxin antagonist was greater in the neighborhood. The effectof auxin and gibberellin was synergistic in inducing these processes. (Received May 23, 1980; )     

Gravity can induce epinastic bending of isolated leaves

Abstract Isolated leaves of Plectranthus fruticosus were grown in cubic plastic cuvettes, and were supplied via their cut petioles with nutrient solution and indole-3-acetic acid (10^?6m ). Holes bored in the cuvette walls allowed the petioles to be oriented at approximately 60°, 90° or 120° to the vertical. Growth of the leaves initially oriented at angles of 60° and 90°, which simulated the situation in the intact plant, did not result in epinastic bending of the petiole. Inversion of the leaves (adaxial surface of the petiole downwards) and orientation of the adaxial/abaxial surfaces of the horizontal petiole parallel to the gravity vector, however, yielded strong epinastic bending of the petioles. In the latter case, this bending was not in the direction of the gravity vector (evidence for point (iii), below). Furthermore, epinastic bending occurred, when the isolated leaves were rotated on a clinostat (petioles parallel to the rotation axis or inclined to the rotation axis at an angle of 30°; 3 r.p.m.). Since a possible influence of the shoot was excluded, it is concluded that (i) perception and response are restricted to the leaf, (ii) gravity alone is sufficient to induce epinasty, (iii) a gravitropic component of the response can probably be excluded. The clinostat induced epinasty may not have been caused by nullifying the effect of gravity but due to continuous gravistimulation of the leaf.     

油茶芽苗砧嫁接口愈合过程解剖学研究

采用石蜡切片法对油茶（Camellia oleifera）芽苗砧嫁接口的愈合过程进行组织解剖学研究。观察结果表明：（1）在嫁接后的第4天,嫁接口产生隔离层;在嫁接后的第8天,嫁接口的砧木产生愈伤组织;在嫁接后的第16天,嫁接口的接穗产生愈伤组织;在嫁接后的第22天,嫁接口的砧木与接穗连接;在嫁接后的第29天,嫁接口的形成层分化形成;在嫁接后的第35天,嫁接口的愈伤组织维管束形成,接穗连接成功。（2）油茶芽苗砧嫁接部位愈伤组织形成前,芽苗砧木的解剖结构在短时间内加速发育,逐渐与接穗的组织结构相似。（3）嫁接口的形成层和其它薄壁细胞组织均能产生愈伤组织,但形成层是其主要来源。     

Studies on Foliar Penetration: IX. PATTERNS OF PENETRATION OF 2,4-DICHLOROPHENOXYACETIC ACID INTO THE LEAVES OF DIFFERENT SPECIES

The comparative patterns of penetration of 2,4-dichlorophenoxyaceticacid (2,4-D) into the leaves of Phaseolus vulgaris, Zea mays,Pisum sativum, Beta wlgaris, Helianthus annuus and Gossypiumhirsuium have been examined. Save for Zea and Gossypium where there is little change withthe stage of leaf development the rates of penetration intoboth surfaces decrease as the leaf matures. The relative ratesare dependent on the species and the age of the leaf but thereare differences between the surfaces. In Phaseolus the characteristicsof primary leaves differ from those of trifoliate leaves sinceonly in immature trifoliate leaves is penetration into the adaxialsurface greater. In darkness the rates of penetration over 24 h remain constantor fall but slightly for all species. Light consistently promotespenetration but with Beta there is a lag before entry is acceleratedinto the abaxial surface as has previously been reported foryoung primary leaves of Phaseolus. For the remaining speciesthe courses of penetration in both light and darkness into bothsurfaces follow similar patterns. As the light intensity isincreased entry is enhanced but the limit of response variesbetween species, between surfaces within species, and in trifoliateleaves of Phaseolus with age. For the six species the order of the relative rates of entryis closely similar whether comparisons are made in light ordarkness or between abaxial and adaxial surfaces: viz. Zea >Helianthus > Phaseolus (primary) > Phaseolus (trifoliate)> Pisum = Beta = Gossypium. The observed specific differencesare discussed in relation to variations in leaf structure, theproperties and thickness of the cuticle and the physiologicaland metabolic processes which influence transport within theepidermal tissues after it has passed through the cuticle bydiffusion.     

QUAESTORA AMPLECTA GEN. ET SP. N., A STRUCTURALLY SIMPLE MEDULLOSAN STEM FROM THE UPPER MISSISSIPPIAN OF ARKANSAS

A well preserved, permineralized seed fern stem is described from the Upper Mississippian Fayetteville Formation of north central Arkansas. Quaestora amplecta gen. et sp. n. is 41.6 cm long and exhibits six pairs of decussate, highly decurrent petiole bases. The stem has a cruciform, exarch protostele with prominent secondary xylem, vascular cambium and secondary phloem. Leaf traces are terete and occur as an outer ring with a small number of internal strands. The cauline vasculature, leaf-trace production, petiolar anatomy and several other features indicate that this specimen represents the most structurally simple and geologically ancient medullosan stem presently recognized.     

STUDIES OF PALEOZOIC FERNS: THE FROND OF ANKYROPTERIS GLABRA

Eggert , Donald A. (Southern Illinois U., Carbondale.) Studies of Palerzoic ferns: The frond of Ankyropteris glabra. Amer. Jour. Bot. 50(4): 379–387. Illus. 1963—The major features of the frond of A. glabra are described on the basis of preserved parts found in Middle Pennsylvanian coal ball material from Illinois. The frond is planated and has well-developed foliar laminae. Primary pinnae arise from the petiole in 2 alternating series, and secondary pinnae arise in a similar fashion from the primary pinnae. Foliar laminae occur on the secondary pinnae and have dichotomous venation. The xylem of the petiole has a diupsilon configuration in the lower part of the axis, while higher in the petiole the xylem forms a strand resembling that of the European species A. westfaliensis. The xylem strands of the primary pinnae arise from the adaxial antennae of the petiolar vascular strand as somewhat C-shapcd bodies and develop antennae and become H-shaped at higher levels. A gap occurs in the antenna of the petiole vascular system above the level of departure of the primary pinna trace. Terete vascular strands occur in the secondary pinna axes which arise from the adaxial antennae of the xylem of the primary pinnae. The foliar laminae are relatively thin, have an irregular outline, and their histology is like that found in many living ferns. The frond of A. glabra illustrates that leaf evolution had progressed in at least one species of the coenopterid family Zygopteridaceae to the extent that an essentially 2-dimensional frond of modern aspect, and with well-developed foliar laminae, was present by Middle Pennsylvanian time.     

中国广义当归属及其相关类群的叶柄结构研究

对中国38种广义当归属及其相关类群植物的叶柄进行了比较解剖学研究,考察了其横切面形状、髓腔的有无、周缘变化、厚角组织的形状和数目,以及维管束的数目和排列等基本特征,为该类群的分类鉴定和系统进化研究提供解剖学依据。结果表明:上述特征呈现出丰富的多样性和良好的种内稳定性,说明叶柄解剖学特征具有重要的分类学意义。综合上述特征,将广义当归属植物及其相关类群的叶柄划分为4个类型:中空环状类型(Ⅰ)、Φ形维管束型(Ⅱ)、U/V形维管束型(Ⅲ)、同心圆形维管束型(Ⅳ)。依据各类型的结构特点,认为该类群叶柄结构可能的演化关系为:实心叶柄是次生类型,中空环形叶柄(单轮环形维管束)相对原始,Φ形维管束型叶柄是过渡类型,而U/V形维管束型和同心圆形维管束型叶柄是相对高级的演化类型。     

Carbohydrate translocation in sugar beet petioles in relation to petiolar respiration and adenosine 5'-triphosphate

Earlier studies have shown that the retarding effect of low petiolar temperatures on sucrose transport through sugar beet (Beta vulgaris L.) petioles is markedly time-dependent. Although the initial effect of chilling the petiole to near 0 C is severely inhibitory, translocation rates soon recover (usually within about 2 hours) to values at or near the control rate. In the present studies, selected metabolic parameters were measured simultaneously with translocation. No stoichiometric relationships among petiolar sucrose transport, petiolar respiration (CO₂ production), and calculated petiolar ATP turnover rates were evident. It appears that the major sources of energy input energizing carbohydrate transport in sieve tubes function mainly at either loading or unloading sites and not at the level of individual sieve-tube elements.