Periclinal Cell Walls Research Articles

Seed Coat Morphology in Gentianopsis (Gentianaceae)

Seed coat morphology is examined in 16 taxa of Gentianopsis, Pterygocalyx, and Gentianella, including representatives from 14 taxa of Gentianopsis, to resolve inconsistencies in previous reports and make new observations using a low vacuum mode of SEM. Four characters are proposed to describe variation in seed coat morphology of this group: (1) the outer periclinal walls of testa; (2) sculpting of inner periclinal walls; (3) seed shape; and (4) seed length. The distinctive papillate seeds of many species of Gentianopsis are the result of inflated outer periclinal walls of testa cells. In some species, the outer periclinal walls of the testa are collapsed inwards, revealing previously unreported sculpting on the inner periclinal walls. Seeds are irregularly angular-ovate or fusiform in Gentianopsis and discoid in Pterygocalyx. Seed length varies from 0.22 to 1.0 mm. These data provide another line of evidence for phylogenetic relationships of Gentianopsis and Pterygocalyx to other members of Swertiinae, and illuminate the affinities of fossil seeds from New England that have been assigned to Gentianopsis.

Anatomia de espécies anfíbias de Cyperaceae de lagoas do semi-árido, BA, Brasil

Foi estudada a anatomia de raízes, rizomas, folhas e escapos de Cyperus odoratus L., Oxycaryum cubense (Poep. & Kunth) Lye e Pycreus macrostachyos (Lam.) Raynal (Cyperaceae-Poales) de lagoas do semi-árido da Bahia visando caracterizar anatomicamente as espécies e levantar estruturas adaptativas à forma de vida anfíbia. As espécies apresentam raízes com epiderme unisseriada, córtex com exoderme e lacunas de ar. Os rizomas apresentam feixes vasculares anfivasais ou colaterais no cilindro vascular. As folhas apresentam epiderme unisseriada, com células de parede periclinal externa mais espessada que a interna, estômatos somente na face abaxial, parênquima clorofiliano alternado com lacunas de ar e feixes vasculares colaterais. Os escapos apresentam epiderme unisseriada, feixes de fibras distribuídos perifericamente alternados com parênquima clorofiliano, lacunas de ar e feixes vasculares colaterais. Oxycaryum cubense difere de Cyperus odoratus e Pycreus macrostachyos por apresentar raízes com pêlos longos, rizomas e estolões com feixes vasculares colaterais, folhas com bordo agudo, e ausência de estrutura Kranz nas folhas e escapos. Características anatômicas como: lacunas de ar observadas principalmente nas raízes, células buliformes na face adaxial da epiderme foliar, hipoderme, reduzido número de elementos xilemáticos e pouca lignificação nas paredes celulares dos tecidos nos diferentes órgãos estudados são consideradas importantes na adaptação dessas plantas anfíbias às lagoas temporárias do semi-árido da Bahia.

Microtubule involvement in the deposition of radial fibrillar callose arrays in stomata of the fern Asplenium nidus L.

Aniline blue staining and callose immunolabeling revealed the deposition of significant callose quantities, in the form of fibrils, in the periclinal walls of guard cells (GCs) of stomata of the fern Asplenium nidus. The stomata that were at an early stage of differentiation displayed short callose fibrils at the junctions of the periclinal walls with the dorsal ones, which converged on the site of the future stomatal pore. In stomata being at an advanced stage of differentiation, callose fibrils were radially arranged around the stomatal pore, while in mature closed ones they were focused on the margins of the wall thickenings lining the stomatal pore. The pattern of the callose fibril organization resembled that of cellulose microfibrils in the same walls. Like the cellulose microfibrils, callose fibrils appeared coaligned with the underlying radial arrays of cortical microtubules (MTs). Moreover, the stomata treated with cellulose synthesis inhibitors (coumarin or dichlobenil) and those recovering from treatments with callose synthesis inhibitors (2-deoxy-D-glucose or tunicamycin) exhibited distinct radial callose fibril arrays. Cytochalasin B did not affect the organization of the radial callose fibril arrays. In contrast, oryzalin completely disturbed the pattern of callose deposition in the affected GCs. Therefore, the fibrillar callose orientation in the periclinal GC walls is probably controlled by MTs but not by actin filaments. The MTs seem to orient callose synthases in the plasmalemma, thus determining the fibrillar nature of callose deposits and their radial mode of arrangement. The cellulose microfibrils are not involved in the callose fibril alignment.

Transgenic Suppression of Cell Death Limits Penetration Success of the Soybean Rust Fungus Phakopsora pachyrhizi into Epidermal Cells of Barley

The basidiomycete Phakopsora pachyrhizi (P. pachyrhizi) causes Asian soybean rust, one of the most devastating plant diseases on soybean. When inoculated on the nonhost barley P. pachyrhizi caused only very small necrotic spots, typical for an incompatible interaction, which involves a hypersensitive cell death reaction. A microscopic inspection of the interaction of barley with P. pachyrhizi revealed that the fungus germinated on barley and formed functional appressoria on epidermal cells. The fungus attempted to directly penetrate through periclinal cell walls but often failed, arrested in plant cell wall appositions that stained positively for callose. Penetration resistance depends on intact ROR1(REQUIRED FOR mlo-SPECIFIED RESISTANCE 1) and ROR2 genes of barley. If the fungus succeeded in penetration, epidermal cell death took place. Dead epidermal cells did not generally restrict fungal development but allowed for mesophyll invasion, which was followed by mesophyll cell death and fungal arrest. Transient or stable over expression of the barley cell death suppressor BAX inhibitor-1 reduced both epidermal cell death and fungal penetration success. Data suggest that P. pachyrhizi provokes a programmed cell death facilitating fungal entry into epidermal cells of barley.

In situ variation in leaf anatomy and morphology of Andira legalis (Leguminosae) in two neighbouring but contrasting light environments in a Brazilian sandy coastal plain

Andira legalis (Vell.) Toledo is a legume shrub widespread along the sandy plains of the Brazilian coast. It occurs both shaded, in forest habitats, or exposed to full sunlight, in the vegetation islands growing on sand deposits. Previous studies reported a high range of morpho-physiological variation for this species along a geographical gradient. This study compared leaf morphology and anatomy of A. legalis in two distinct but adjacent light environments: a dense forest (shaded) and a scrub of Palmae (exposed). We studied the amplitude of variation for these traits within a small (0.5 ha) geographical area. Leaf anatomy parameters were measured for five leaves collected from five plants in each habitat. The parameters measured were leaf and mesophyll thickness, thickness of the outer periclinal cell wall, thickness of the adaxial and abaxial epidermis and vascular bundle transversal section area, and also common epidermal cells, stomata and trichome density. Leaf morphology parameters were obtained from five leaves of each of 20 plants in each site. Dry and fresh weights were measured to obtain leaf specific mass and succulence. All anatomy and morphology parameters, except trichome density, were significantly higher for the sun-exposed plants. Less expected, however, was the marked qualitative difference between exposed and shaded plants: in the former the mesophyll had a unilateral symmetry (i.e., the whole mesophyll occupied by photosynthetic tissue), whereas in the latter there was a dorsiventral symmetry (i.e., partly palisade and partly spongy parenchyma). Such amplitude of variation shows that even within a small geographic area A. legalis has a broad ecological plasticity.

Ornamentación del antecio superior en Urochloa y géneros vecinos (Poaceae, Panicoideae, Paniceae): su valor sistemático

Salariato, D.; O. Morrone & F. O. Zuloaga. 2008. Ornamentation pattern of the upper anthecium in Uroch- loa and related genera (Poaceae, Panicoideae, Paniceae): its systematic value. Darwiniana 46(2): 335-355. The ornamentation pattern of the upper anthecium in species of Paniceae belonging to the PCK group, in particular of the genus Urochloa, was analyzed. Nineteen different ornamentation patterns were recognized, of which 11 are reported for the first time. Several epidermal elements are described, including simple papillae, compound papillae and ridges in the anticlinal or periclinal cell walls. The ornamentation patterns were useful for infrageneric delimitation in the genus Urochloa but not to deli- mit the genus from related ones; on the contrary, this character provided more evidence to sustain the paraphyly of the genus. Systematic and phylogenetic value of this character in Urochloa and other rela- ted genera are also discussed.

Aleurone Cell Walls of Wheat Grain: High Spatial Resolution Investigation Using Synchrotron Infrared Microspectroscopy

Infrared microspectroscopy and immunolabeling techniques were employed in order to obtain deeper insight into the biochemical nature of aleurone cell walls of wheat grain. The use of a synchrotron source, thanks to its intrinsic brightness, has provided unprecedented information at the level of a few micrometers and has allowed the discrimination of various polysaccharides in cell walls. The high spectral quality obtained in the small analyzed domain has been beneficial in estimating the relative proportions of beta-glucan and arabinoxylan, through the use of principal component analysis (PCA). The highest amount of beta-glucan is found in periclinal cell walls close to the starchy endosperm. The junction regions between aleurone cells are enriched in arabinoxylan. At the early stage of wheat grain development (271 degrees D), the chemical composition along the cell walls is more heterogeneous than at the mature stage. Both synchrotron infrared microspectroscopy and immunolabeling experiments made it possible to reveal the spatial heterogeneity of the various chemical compositions of aleurone cell walls.

Anatomia e ultra-estrutura foliar de Cyperus maritimus Poir. (Cyperaceae): estratégias adaptativas ao ambiente de dunas litorâneas

Foram analisados aspectos anatômicos e ultra-estruturais foliares de Cyperus maritimus Poir. visando identificar caracteres adaptativos ao ambiente de dunas litorâneas. Para isto, indivíduos ocorrentes nas dunas da Praia de Pipa, Rio Grande do Norte, Brasil, tiveram as folhas submetidas a diferentes análises: microscopia de luz, eletrônica de varredura e de transmissão. Em vista frontal, a epiderme possui tricomas unicelulares, corpos de sílica, cutícula estriada e depósitos de cera. Em secção transversal, a epiderme é unisseriada com parede periclinal externa espessa. Os estômatos são paracíticos, podendo o ostíolo estar obstruído por cera. Abaixo da face adaxial observa-se o parênquima aqüífero. Os feixes vasculares ocorrem em múltiplas fileiras, sendo as periféricas compostas por feixes de diâmetro menor que os feixes da fileira central. Foram observados caracteres relacionados à síndrome Kranz do tipo clorociperóide. Aspectos ultra-estruturais, como cloroplastos presentes na bainha do feixe, esses sem grana evidentes, entre outras características, reforçam a possível ocorrência da via C4 nesta espécie. É a primeira citação para o gênero Cyperus de cloroplasto nas celulas do tecido vascular. Neste trabalho foi possível observar vários caracteres importantes para plantas submetidas a estresse hídrico e salino, como: cera, células epidérmicas com parede periclinal externa espessada, parênquima aqüífero e síndrome Kranz.

Surface replicas of normal and vitrified leaves of Datura insignis, Barb Rodr

Vitrification is a morphological and physiological disorder affecting plants during their in vitro vegetative propagation. Vitrified plants have a poor survival rate when transferred from in vitro to greenhouse conditions, a fact mainly due to water loss and dissecation. It has been shown that normal and vitreous leaves of Datura insignis differ in the frequency of normal and abnormal stomata. The purpose of this work was to compare the surface of normal and vitreous leaves of D. insignis, using a modification of the platinum/carbon replica method. Adaxial and abaxial leaf surfaces of normal plantlets have a smooth and homogenous cuticle. A granular aspect, probably due to leaf age, rarely occurs at the periphery of the epidermal cells. Both adaxial and abaxial leaf surfaces of vitrified plantlets show discontinuities in the cuticle, occurring at several regions of the outer periclinal cell walls. However, such discontinuities are most noticeable in the region between adjacent epidermal cells. Fibrils 20-30 nm thick show a random arrangement or an oriented pattern in cuticular discontinuities. In D. insignis vitrified plantlets, adaxial and abaxial leaf cuticle has discontinuities or gaps which may cause an increase in cuticular transpiration contributing to the low survival rate of vitrified plantlets.

Induction of wall ingrowths of transfer cells occurs rapidly and depends upon gene expression in cotyledons of developing Vicia faba seeds

Abaxial epidermal cells of developing faba bean (Vicia faba) cotyledons are modified to a transfer cell morphology and function. In contrast, the adaxial epidermal cells do not form transfer cells but can be induced to do so when excised cotyledons are cultured on an agar medium. The first fenestrated layer of wall ingrowths is apparent within 24 h of cotyledon exposure to culture medium. The time course of wall ingrowth formation was examined further. By 2 h following cotyledon excision, a 350 nm thick wall was deposited evenly over the outer periclinal walls of adaxial epidermal cells and densities of cytoplasmic vesicles increased. After 3 h in culture, 10% of epidermal cells contained small projections of wall material on their outer periclinal walls. Thereafter, this percentage rose sharply and reached a maximum of 90% by 15 h. Continuous culture of cotyledons on a medium containing 6-methyl purine (an inhibitor of RNA synthesis) completely blocked wall ingrowth formation. In contrast, if exposure to 6-methyl purine was delayed for 1 h at the start of the culture period, the adaxial epidermal cells were found to contain small wall ingrowths. Treating cotyledons for 1 h with 6-methyl purine at 15 h following cotyledon excision halted further wall ingrowth development. We conclude that transfer cell induction is rapid and that signalling and early events leading to wall ingrowth formation depend upon gene expression. In addition, these gene products have a high turnover rate.

Presumable role of plasmodesmata in floral signal transduction in shoot apical meristems of rudbeckia and perilla plants

The number of plasmodesmata was calculated per 1 μm of cell wall length in the central and medullar zones of shoot apical meristems (SAM) in the course of floral transition in a long-day (LD) plant Rudbeckia bicolor Nutt. and a short-day plant Perilla nankinensis Lour. Under the day length unfavorable for flowering (control), the numbers of plasmodesmata differed in the central and medullar zones of SAM, which produce the reproductive organs and stems, respectively. Besides, the numbers of plasmodesmata in the central zone of perilla SAM considerably differed between the anticlinal and periclinal cell walls of the first and second cell layers. Following the photoperiodic induction (PI) with eight LD in rudbeckia and twelve SD in perilla favorable for floral transition, the numbers of plasmodesmata considerably increased in the anticlinal and periclinal cell walls of the first and second cell layers of the central zone; meanwhile in the medullar zone, the numbers of plasmodesmata dropped down following PI. These data show that floral transition presumably involves the activation of cell-to-cell interactions and enhances the signal transduction in SAM.

Seed morphology of some species of Convolvulaceae from Egypt (Identification of species and systematic significance)

AbstractSeed morphology of 31 taxa belong to six genera of Convolvulaceae from Egypt were examined by using light and scanning electron microscopy. Macro‐ and micromorphological characters, including seed shape, colour, size, surface, epidermal cell shape, anticlinal boundaries, outer periclinal cell wall and relief of outer cell walls, are presented. Three types of basic anticlinal cell wall boundaries and three types of relief outer cell walls are recognized and four different shapes of the outer periclinal cell wall are described. A key for the identification of the investigated taxa based on seed characters is provided. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Seed morphology of Cuscuta L. (Convolvulaceae) in Egypt and its systematic significance

AbstractThe seed morphology of eight taxa of Cuscuta from Egypt has been studied using light and scanning electron microscopy, to determine the significance of seed coat features as taxonomic characters. Macro‐ and micromorphological characters, including seed shape, colour, size, epidermal cell shape, anticlinal boundaries, outer periclinal cell wall and relief of outer cell walls are presented. Three types of anticlinal cell wall boundaries are recognized and two different shapes of outer periclinal cell wall are described. The secondary sculpture of the cell wall varies from striate to micro‐reticulate, and smooth to fine folds. A key for the identification of the investigated taxa based on seed characters is provided. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plastid Movement Impaired 2, a New Gene Involved in Normal Blue-Light-Induced Chloroplast Movements in Arabidopsis

Chloroplasts move in a light-dependent manner that can modulate the photosynthetic potential of plant cells. Identification of genes required for light-induced chloroplast movement is beginning to define the molecular machinery that controls these movements. In this work, we describe plastid movement impaired 2 (pmi2), a mutant in Arabidopsis (Arabidopsis thaliana) that displays attenuated chloroplast movements under intermediate and high light intensities while maintaining a normal movement response under low light intensities. In wild-type plants, fluence rates below 20 micromol m(-2) s(-1) of blue light lead to chloroplast accumulation on the periclinal cell walls, whereas light intensities over 20 micromol m(-2) s(-1) caused chloroplasts to move toward the anticlinal cell walls (avoidance response). However, at light intensities below 75 micromol m(-2) s(-1), chloroplasts in pmi2 leaves move to the periclinal walls; 100 micromol m(-2) s(-1) of blue light is required for chloroplasts in pmi2 to move to the anticlinal cell walls, indicating a shift in the light threshold for the avoidance response in the mutant. The pmi2 mutation has been mapped to a gene that encodes a protein of unknown function with a large coiled-coil domain in the N terminus and a putative P loop. PMI2 shares sequence and structural similarity with PMI15, another unknown protein in Arabidopsis that, when mutated, causes a defect in chloroplast avoidance under high-light intensities.

Herbicide effects on cuticle ultrastructure in Eleusine indica and Portulaca oleracea

Eleusine indica and Portulaca oleracea are two common weeds in peanut crops in southern Córdoba. Two chemicals are frequently used to control them, quizalofop for grasses and lactofen for dicots. The objective is to study the effects of quizalofop and lactofen on cuticle ultrastructure in E. indica and P. oleracea, respectively. In the lab, quizalofop was applied on E. indica and lactofen on P. oleracea. Three plant categories were analyzed in each species: 3, 1-2, and no tiller in E. indica, and 8, 6, and 2 nomophylls in P. oleracea. Leaf samples from both species were collected at 7 and 16 days post-application and were treated for scanning electron microscopy. E. indica cuticle treated with lethal dose shows areas where epicuticular waxes disappear, specially in the youngest individuals. These areas are located predominantly on periclinal walls of typical epidermic cells and subsidiary cells. On the other hand, P. oleracea shows cuticle discontinuities that may be caused by lactofen entry. They are smaller and less frequent in plants having 8 or more nomophylls. The remaining waxes act as a herbicide accumulation compartment and, therefore, would partially prevent the active ingredient entry to epidermic cells.

Apical intrusive growth of cambial fusiform initials along the tangential walls of adjacent fusiform initials: evidence for a new concept

A new study of cambium of Pinus sylvestris L., Tilia cordata Mill. and Wisteria floribunda (Willd.) DC provides fresh clues on the cambial dynamics, rejecting the hitherto held concept that intrusive growth of the fusiform initial occurs between the radial walls of adjacent initials. It demonstrates that intrusion of the elongating initial in fact takes place along tangential walls of adjacent fusiform initials and their immediate derivatives. It also suggests a new mechanism for ‘elimination of initials’. Intrusive growth of the fusiform initial was found to begin with development of characteristic slants, representing a transitional stage of the process of transformation of periclinal walls of fusiform initial cells into radial walls, as observed in transverse sections of active cambium. The gradually progressing event comprised (a) appearance of either a triangular microspace limited by two periclinal walls of a fusiform initial and its derivative and one radial wall of another fusiform initial in the adjacent radial file, or a rhomboidal microspace enclosed by four periclinal walls of two laterally adjacent fusiform initials and their immediate derivatives, (b) intrusion of elongating tip of fusiform initial from neighbouring file into the microspace thus formed, (c) symplastic growth of the cambial cell walls in radial direction, (d) unequal periclinal divisions of fusiform initial cells while growing intrusively, and (e) unequal periclinal divisions of derivative cells not growing intrusively. Intrusive growth between periclinal walls affected rearrangement of the fusiform initials but did not add to the cambial circumference. The existing concepts of (a) intrusion of the fusiform initial between radial walls of neighbouring initials and (b) elimination of fusiform initials from cambial surface have been reassessed and redefined.

Ontogenetic variation in chemical and physical characteristics of adaxial apple leaf surfaces

The reaction of plants to environmental factors often varies with developmental stage. It was hypothesized, that also the cuticle, the outer surface layer of plants is modified during ontogenesis. Apple plantlets, cv. Golden Delicious, were grown under controlled conditions avoiding biotic and abiotic stress factors. The cuticular wax surface of adaxial apple leaves was analyzed for its chemical composition as well as for its micromorphology and hydrophobicity just after unfolding of leaves ending in the seventh leaf insertion. The outer surface of apple leaves was formed by a thin amorphous layer of epicuticular waxes. Epidermal cells of young leaves exhibited a distinctive curvature of the periclinal cell walls resulting in an undulated surface of the cuticle including pronounced lamellae, with the highest density at the centre of cells. As epidermal cells expanded during ontogenesis, the upper surface showed only minor surface sculpturing and a decrease in lamellae. With increasing leaf age the hydrophobicity of adaxial leaf side decreased significantly indicated by a decrease in contact angle. Extracted from plants, the amount of apolar cuticular wax per area unit ranged from only 0.9 μg cm −2 for the oldest studied leaf to 1.5 μg cm −2 for the youngest studied leaf. Differences in the total amount of cuticular waxes per leaf were not significant for older leaves. For young leaves, triterpenes (ursolic acid and oleanolic acid), esters and alcohols were the main wax components. During ontogenesis, the proportion of triterpenes in total mass of apolar waxes decreased from 32% (leaf 1) to 13% (leaf 7); absolute amounts decreased by more than 50%. The proportion of wax alcohols and esters, and alkanes to a lesser degree, increased with leaf age, whereas the proportion of acids decreased. The epicuticular wax layer also contained α-tocopherol described for the first time to be present also in the epicuticular wax. The modifications in the chemical composition of cuticular waxes are discussed in relation to the varying physical characteristics of the cuticle during ontogenesis of apple leaves.

Ontogenic Changes in Epicuticular Wax and Chloroplast Integrity of a Cotton (Gossypium hirsutum L.) Leaf

The progressive decline in cotton leaf photosynthesis with season could be accounted for by gaining an insight into ontogenic changes in chloroplast integrity and epicuticular wax ultrastructure. Therefore, the sequence of ultrastructural changes in chloroplast and epicuticular wax morphology were probed in 10-, 20-, 40-, and 60-d-old cotton (Gossypium hirsutum L.) leaves using electron microscopy. Scanning electron microscopy illustrated that the epicuticular wax on the periclinal walls of the convex epidermal cells occurred as striations and persisted as such during the course of leaf aging. The degree of wax spread, however, increased as the leaf progressed towards senescence. Transmission electron microscopy revealed that a 20-d-old photosynthetically active leaf possessed healthy chloroplasts (6.8 μm long and an area of 9.7 μm2) with absolute membrane integrity depicted by large appressed grana stacks of thylakoids interconnected by non-appressed stroma lamellae. The thylakoid membrane network was oriented parallel to the long axis of the chloroplast and a few small plastoglobuli (1.85 μm2) scattered in the stroma. Conversely, membrane integrity was lost with leaf age after 20 d as evidenced by disruption of the grana and stroma lamellae. Concurrent with the membrane damage, extensive occlusion of chloroplast by several large spherical plastoglobuli (5.68 μm2) occurred, the rate of occlusion increased with leafage distending the chloroplast as evidenced by proliferation of its cross-sectional area (12.8 μm2). Of particular interest was the finding that the plastoglobuli ensued through the chloroplast envelope into the cytoplasm. The progressive loss of chloroplast membrane integrity coupled with increased leaf waxiness may have limited photosynthetic activities of cotton leaves during senescence.

Anatomy of salt excretory structures in certain halophytes in Egypt with a special reference to their re- naming and classification

The anatomy of salt excretory structures was studied in 22 dicotyledonous and monocotyledonous halophytic species; 13 of which were not previously investigated. The material was selected to represent obligate and facultative, and succulent and non- succulent halophytes. Structural variations led to their re- naming and classification. For more precise naming it was believed that one should differentiate between ‘glands’ that have no ontogenic relation to the epidermis and the epidermal appendages, and convinced by this, the excretory structures were classified into three types and two sub-types. It was also concluded that the presence of such structures in facultative halophytes, where the concerned stress factor (salinity) is absent, makes it a hereditary character resulting in an adaptive capacity for salt tolerance. Ectodesmata were recorded in the outer periclinal walls of the epidermal cells in some species and were considered to be another mechanism for salt excretion.

Intensive change of inclination of cambial initials in Picea abies (L.) Karst. tumours

Changes in the inclination of cambial fusiform cells producing wavy grain wood in spruce trunk tumours were investigated. The rate of changes of cell inclination depends on events such as intrusive growth between periclinal walls of cells of neighbouring files and unequal periclinal divisions. Intrusive growth of initial cell ends between radial walls does not affect the change in cell inclination. The only reason for such change is the intrusive growth of initial cell ends between periclinal cell walls of neighbouring files. Initial cells do not form a continuous, integral layer. After periclinal division of initial cells the status of the initial is defined by the initial surface. After periclinal divisions of mother cells packets of cells are produced. In cambium, which does not rearrange, packets of cells originating from the same initial cell are located in one file. Cells in these packets do not usually grow intrusively and do not change their position. In tumorous cambium, packets are dislocated in periclinal planes. In the tangential surface a very large and rapid change in inclination of fusiform cells was observed. In spite of this change, which causes heterogeneous files, the order (arrangement) of the files was not disturbed.