Periclinal Cell Divisions Research Articles

Ontogeny and morphology of ovarian and fruit hairs in Kiwifruit

Abstract The initiation and development of ovarian and fruit hairs in Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward was studied using light and scanning electron microscopy. The morphology and distribution of large and small hairs are described. Hairs are initiated from one epidermal cell at an early stage of ovary development at around 21 days after vegetative bud burst. They develop through periclinal and anticlinal cell division into a tapering multiseriate structure, approximately 2.5 mm in length, which terminates in one very long apical cell approximately 1 mm in length. Sub-epidermal tissue contributes to the multiseriate base beginning when four layers of cells have been produced (about 45-60 days from bud burst). These hairs, then, are technically emergences. New hairs continue to form between developing hairs until epidermal cell division ceases at around 107-114 days after bud burst. The small hairs present on mature fruit may be an arrested early stage of development of large hairs. No stomata were observed on the ovary or fruit surface using light or scanning electron microscopy.

The Relationship Between the Distribution of Periclinal Cell Divisions in the Shoot Apex and Leaf Initiation

The Relationship Between the Distribution of Periclinal Cell Divisions in the Shoot Apex and Leaf Initiation

STRUCTURAL CHANGES IN THE APEX OF THE FEMALE STROBILUS AND THE INITIATION OF THE FEMALE REPRODUCTIVE ORGAN (OVULE) IN EPHEDRA DISTACHYA L. AND E. EQUISETINA BGE

SUMMARY Histological changes in the apex of the female strobilus and the initiation of the reproductive organ (ovule) were investigated in two species of Ephedra. In contrast to the vegetative shoot apex, periclinal cell divisions take place frequently in the dermal layer of the apex of the female strobilus and of the ovule. These divisions in the former begin at the summit before the initiation of the ovule, or they begin at both the summit and peripheral region simultaneously with the ovular initiation. Two ovule primordia originate from the axils of the uppermost bracts by mitotic activity in the subdermal region, their outer part becoming two-layered as the result of regular periclinal divisions in the dermal cells. As compared with the ovule primordia, the residual shoot apex between the ovule primordia shows less periclinal cell divisions just before and after it becomes discernible. The occurrence of these divisions in the apex of the female strobilus and in the ovule primordia is compared with that in the male ones.

DEVELOPMENTAL ANATOMY AND HISTOCHEMISTRY OF LIGHT‐INDUCED CALLUS FORMATION BY DIÖON EDULE (ZAMIACEAE) SEEDLING ROOTS IN VITRO

Light exposure caused massive areas of callus to develop from primary roots of aseptically cultured Diöon edule seedlings. Callus initiation and continued growth was due to cortical cell hypertrophy and subsequent periclinal cell division. Callus initiation occurred in the subdermal cortex and developed radially and centripetally from the locus of initiation. Callus formation encompassed virtually all of the cortex, but did not incorporate any of the vascular tissues. With very large calluses, sectors of internal periderm arose between the developing callus and the remaining quiescent cells of the inner cortex. Most of the callus cells were typical, vacuolate parenchyma with cellulose walls, and large, multilobed amyloplasts. Callus also contained idioblasts with globular deposits of polyphenols. Adjacent cortical cells were typical parenchyma with peripheral cytoplasm, but contained small plastids with little starch accumulation.

FLORAL ONTOGENY IN CYCLAMEN PERSICUM ‘F‐1 ROSEMUNDE ROSE’ (PRIMULACEAE)

Floral ontogeny was examined in Cyclamen persicum ‘F‐1 Rosemunde Rose’ using a combination of light and scanning electron microscopy. The leaf plastochron index (LPI), earlier calculated for leaf elongation, was used to determine the length of each stage of floral development. LPI will provide a useful tool for selecting flowers of a given stage from large plant populations or from plants where flowers are small or inaccessible during early ontogenetic stages. Most features of floral development are similar to those previously described for other primulaceous genera. The petal‐stamen relationship, however, is unusual; stamens arise through periclinal cell divisions in the adaxial surface layers of common petal‐stamen primordia. Anatomical evidence suggests that the placenta is formed both by appendicular initials which give rise to the ovules and ventral carpellary bundles, and receptacular cells which form some, if not all, of the central axis.

Tissue origins, cell lineages and patterns of cell division in the developing dermal system of the frut of Vitis vinifera L.

Cell division during development of the dermal system of fruit of the grape cv. Gordo is confined to the first growth period. The epidermis is conserved with anticlinal proliferative cell divisions providing for increase in cell number. The hypodermis is the layer of origin of the collenchymatous dermal system. Six or seven layers are differentiated by periclinal cell divisions early in the first growth period, and later increase in size is obtained by proliferative anticlinal cell divisions. These observations are related to developmental and genetic control of fruit shape and volume.

Early modifications of the internodal anatomy of Glycine max sprayed with 2,4-DB

An aqueous spray of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) induces anatomical changes in young Glycine internodes. Four days after spraying, the first symptoms appear outside the cambium when the interfascicular parenchyma cells and the adjacent cortical parenchyma cells enlarge and divide in several planes. Four days later, the metaphloem parenchyma cells in many of the leaf traces undergo considerable periclinal cell division and extensive radial cell enlargement. The phloem parenchyma cells of the late metaphloem and first secondary phloem enlarge and divide in a less orderly fashion. Fifteen days after treatment, the cortical parenchyma is modified into a band of radially seriate cells above the protophloem fibers. Products of this cambium-like region convert the cortex into a callus-like tissue. The size of starch grains is reduced initially in the phloem and xylem and later in the cortex. It appears that the stimuli produced by 2,4-DB move into the internode via the metaphloem of leaf traces. Despite the rapid obliteration of conducting phloem by the 2,4-DB induced stimulation of phloem parenchyma, an accelerated differentiation of secondary phloem compensates for this loss.

Development and Histochemistry of the Pistil of the Grape, Vitis vinifera

The development of the grape pistil is followed for a period of 9 weeks from flower initiation to anthesis. Three phases of pericarp differentiation are revealed: ring meristem formation; cell proliferation by anticlinal cell divisions; and a maturation phase characterized by periclinal cell division and differentiation. Both the stigma papillae and the transmitting tissue of the style originate by periclinal cell divisions. The receptive stigma is of the wet type and comprises many filamentous papillae, each composed of about 20 cells and covered by a loose cuticle. The stigma exudate shows similar cytochemical properties to the material in the intercellular spaces of the transmitting tissue and is physically continuous with it. After pollination and coincident with withering of the stigma, a single layer of stylar cells becomes suberized, forming a protective layer of cicatrix.

Generic Circumscription in the Family Ectocarpaceae (Phaeophyceae)

The family Ectocarpaceae currently contains the simplest, and probably also the most primitive, members of the Phaeophyceae. The thallus form of every species is a heterotrichous filament with little or no structural modification. Some species may possess quite extensive cortication of axial filaments by adventitious rhizoids but advanced pseudoparenchyma is never formed. Periclinal cell divisions within filaments have also been reported, particularly in the course of sporangium development, but true parenchyma is unknown. Growth of the erect system of filaments is diffuse, for although intercalary sites of relatively active cell division may sometimes be observed, these lack the permanence of position and sustained activity of true intercalary meristems. The growth of the horizontal branch system is probably mainly apical, but is also too diffuse to be considered meristematic. Sporangia and gametangia are formed from vegetative cells and occur either as intercalary structures within filaments or as modified branch apices. Sexual fusion of gametes may be isogamous or anisogamous.

INFLORESCENCE DEVELOPMENT IN BRASSICA CAMPESTRIS L.

Vegetative seedlings of the Ceres strain Brassica campestris L., a quantitative, long‐day plant, were induced to flower by exposure to a 16‐hr, long‐day cycle. Cytohistological and cytohistochemical changes associated with inflorescence development were examined. Developing shoot apices were classified in vegetative, transitional, and reproductive stages. The vegetative apex possessed a biseriate tunica, central zone, peripheral zone and pith‐rib meristem. The transitional stage at 48 hr was marked by an increase in size and by a stratification of the upper cell layers of the shoot apex with a concurrent decrease of apical cytohistochemical zonation. The reproductive stage was initiated at 58 hr by periclinal cell divisions in the 3rd and 4th cell layers of the flank region. Cytohistochemical zonation in the vegetative apical meristem was restored in the floral apex. An “intermediate developmental” phase was not observed between the vegetative and reproductive stage.

Inflorescence Development in Brassica campestris L.

Vegetative seedlings of the Ceres strain Brassica campestris L., a quantitative, long-day plant, were induced to flower by exposure to a 16-hr, long-day cycle. Cytohistological and cytohistochemical changes associated with inflorescence development were examined. Developing shoot apices were classified in vegetative, transitional, and reproductive stages. The vegetative apex possessed a biseriate tunica, central zone, peripheral zone and pith-rib meristem. The transitional stage at 48 hr was marked by an increase in size and by a stratification of the upper cell layers of the shoot apex with a concurrent decrease of apical cytohistochemical zonation. The reproductive stage was initiated at 58 hr by periclinal cell divisions in the 3rd and 4th cell layers of the flank region. Cytohistochemical zonation in the vegetative apical meristem was restored in the floral apex. An “intermediate developmental” phase was not observed between the vegetative and reproductive stage.

Floral development of Aponogeton natans and A. undulatus

The primordia of the floral appendages are initiated in an acropetal succession. Members of the same whorl appear nearly simultaneously. The gynoecial whorl and the two staminal whorls are trimerous, whereas the perianth consists only of two anteriolateral tepals. However, the posterior (adaxial) tepal may be present as an extremely reduced buttress whose growth becomes arrested immediately after its inception. If this somewhat questionable tepal rudiment is included we have a perfectly trimerous and tetracyclic flower with alternation of successive whorls. Subtending bracts of the flowers are completely missing in all developmental stages. While the tepal primordia are dorsiventral from their inception, the stamen and pistil (carpel) primordia originate as hemispherical mounds which become dorsiventral in subsequent stages of development. Each pistil (carpel) primordium becomes horseshoe shaped. As the margins grow up and contact they fuse postgenitally. No cross zone is formed. Placentation is submarginal. In A. natans eight ovules are formed and in A. undulatus only two arise; all ovules are bitegmic. The floral apices have a two-layered tunica up to the stage of pistil formation. The inception of all floral appendages (including the ovules) occurs by periclinal cell division in the second tunica layer. The third layer (corpus) may contribute to the formation of the stamens and pistils. Each appendage primordium receives only one procambial strand which begins to differentiate after the inception of the primordium. The questionable rudimentary tepal buttress lacks a procambial strand. Apparently it does not reach the developmental stage at which procambial induction occurs. From the point of view of floral development, the two species of Aponogeton differ drastically from members of the Alismatales studied so far. Among the Helobiae, the Aponogetonaceae appear to be most closely related to the Scheuchzeriaceae and the Juncaginaceae (Triglochinaceae).

A re-examination of the mucilage duct system ofNereocystis luetkeana (Mertens) postel and ruprecht, (Phaeophyta)

The inception of the mucilage duct system and its structural relationship to the zoosporangial sori of the sporophyte ofNereocystis have been re-examined. Light microscope observations are presented here which demonstrate that both mucilage duct lumen and secretory cell differentiation occur exclusively and simultaneously in the meristoderm layer. Both of these events are associated with a special periclinal division of individual meristoderm cells on either side of the transition zone. Secretory cell differentiation is characterized by a maintenance of secretory and limited meristematic activity. The duct lumen arises schizogenously in the anticlinal walls adjacent to meristoderm cells and the continuance of this results in the potential venting points of maturity. Consequently, inNereocystis the extracellular lumen of the sorus is not confluent with the lumen of the mucilage ducts when undisturbed. In soral regions the potential venting points may be disrupted in a manner similar to that achieved artificially in the laboratory to assist in fluishing zoospores from the sorus surface.

On the Cortex Formation in the Apical Meristems of the Elongating Crown Roots of Rice Plants

The process of cortex formation in the apical meristems of normally elongating crown roots of rice plants was studied by observing cell arrangement and cell divisions. All longitudinal cell files in cortex of a root branched from the endodermal cell file (Fig.2). The branchings mostly occurred within 200 μm of the meristem tip (intersecting point of root axis with cap boundary). Consequently, the number of cortical cell layers decreased toward the meristem tip. Cortical cells dividing transversely were found as far as about twice the root diameter from the meristem tip (Fig. 7). The frequency of transverse cell divisions decreased gradually toward the meristem tip, from the 150 μm level in roots thicker than 600 μm in diameter and from the l00 μm level in thinner roots (Fig. 8). In thicker roots, no transverse division was seen in parts more distal than 50 μm. Periclinal cell divisions occurred only in endodermal cells near the meristem tip where transverse division frequency and layer number of cortical cells decreased (Fig.11). Most endodermal cells dividing periclinally are those from which cortical cell files are branched in a basal direction (Fig. 9). In thicker roots, periclinal divisions occurred in endodermal cells 50 μm-200 μm distant from the meristem tip; and in thinner roots, in those within 150 μm (Fig. 8). The transverse cell divisions in the most distal part of cortex with less number of cell layers are considered to decrease the number of cortical cell layers by sending this part in the basal direction. Thus, thicker roots with less frequency of transverse cell division in distal part of meristematic cortex tend to maintain their layer numbers in comparison with thinner roots. The periclinal cell divisions in endodermal cells act as if they compensate for the decrease in the number of cortical cell layers.

Developmental Anatomy of Interlocular Cavitation in Snap Beans Phaseofus vufgaris L.1

Abstract Developmental anatomy of interlocular cavitation (IC), defined as the formation of cavities in soft parenchymatous endocarp cells between seed locules4, was studied in pods of several snap bean cultivars grown under various cultural and environmental conditions during the years 1969–1972. IC occurred in pods from the stages of rapid pod elongation (6–10 days after anthesis) until the time of pod senescence. Unbalanced swelling of endocarp tissues combined with decreased periclinal cell division and rapid cell elongation are concluded to be the causes of IC. In the most commonly observed form, IC also includes the separation of fused endodermal cells. Pod malformation is greater in pods with severe IC and such pods exhibited more quality defects after processing. Sequential development of this developmental and physiological disorder is illustrated.

POSTGENITAL CARPEL FUSION IN CATHARANTHUS ROSEUS (APOCYNACEAE). I. LIGHT AND SCANNING ELECTRON MICROSCOPIC STUDY OF GYNOECIAL ONTOGENY

The detailed ontogeny of postgenital fusions within the gynoecium of Catharanthus roseus was investigated. The basal margins of the young carpel primordia infold and fuse together to seal shut the loculi. Independently, the opposing distal tips of the two carpels also unite, with the fusion region subsequently developing into the stigma, style, and a small distal region of the compound ovary. The basal ovary regions of the two opposing carpels remain unfused, thus leaving the tip fusion spatially restricted. In the region of contact, cells with distinctively epidermal features progressively lose their epidermal character after their participation in the fusion. In the fused stigma these former epidermal cells redifferentiate into transmitting and secretory tissues; in the fused style these cells undergo a tremendous expansion in length while forming stylar transmitting tissue; but in the compound ovary region corresponding cells experience little expansion or redifferentiation. It is concluded that the loss of epidermal features or the occurrence of periclinal cell divisions in the epidermis is a definitive indication that cells have fused postgenitally. However, studies with the transmission electron microscope are necessary to detect the first indications of a postgenital fusion. The compound ovary region within the gynoecium of C. roseus is a tissue appropriate for a high resolution ultrastructural study of the cytological events accompanying postgential tissue fusion because the fusion occurs quickly and little subsequent cell expansion takes place within this region.

Postgenital Carpel Fusion in Catharanthus roseus (Apocynaceae). I. Light and Scanning Electron Microscopic Study of Gynoecial Ontogeny

The detailed ontogeny of postgenital fusions within the gynoecium of Catharanthus roseus was investigated. The basal margins of the young carpel primordia infold and fuse together to seal shut the loculi. Independently, the opposing distal tips of the two carpels also unite, with the fusion region subsequently developing into the stigma, style, and a small distal region of the compound ovary. The basal ovary regions of the two opposing carpels remain unfused, thus leaving the tip fusion spatially restricted. In the region of contact, cells with distinctively epidermal features progressively lose their epidermal character after their participation in the fusion. In the fused stigma these former epidermal cells redifferentiate into transmitting and secretory tissues; in the fused style these cells undergo a tremendous expansion in length while forming stylar transmitting tissue; but in the compound ovary region corresponding cells experience little expansion or redifferentiation. It is concluded that the loss of epidermal features or the occurrence of periclinal cell divisions in the epidermis is a definitive indication that cells have fused postgenitally. However, studies with the transmission electron microscope are necessary to detect the first indications of a postgenital fusion. The compound ovary region within the gynoecium of C. roseus is a tissue appropriate for a high resolution ultrastructural study of the cytological events accompanying postgential tissue fusion because the fusion occurs quickly and little subsequent cell expansion takes place within this region.

LEAF DEVELOPMENT IN DOXANTHA UNGUIS‐CATI (BIGNONIACEAE)

Leaf structure in Doxantha unguis‐cati is polymorphic. The usual mature compound leaf is composed of two lanceolate leaflets and a terminal tripartite spine‐tendril. Leaf primordia are initiated simultaneously in pairs on opposite flanks of the shoot apical meristem by periclinal cell divisions in the third subsurface layer of the peripheral flank meristem. Two leaflet primordia are the first lateral appendages of the compound leaf. Initiation of these leaflet primordia occurs on the adaxial side of a compound leaf primordium 63–70 μm long. Lamina formation is initiated at the base of a leaflet primordium 70–90 μm long and continues acropetally. Mesophyll differentiation occurs in later stages of development of leaflets. The second pair of lateral appendages of the leaf primordium differentiate as prongs of the tendril. Initiation of the second pair of lateral appendages occurs on the adaxial side of a primordium approximately 168 μm long. Acropetal procambialization and vacuolation of cells extend to the apex of tendrils about 112 μm long, restricting the tendril meristem to the adaxial side of the primordium and resulting in curvature of the tendril. The tendril meristem is gradually limited to a more basipetal position as elongation of apical cells continues. Initiatory divisions and early ontogenetic stages of leaflets and tendrils are similar. Their ontogeny differs when the lateral primordia are approximately 70 μm long. Marginal and submarginal initials differentiate within leaflets but not in tendrils. Apical growth of tendrils ceases very early in ontogeny as compared with leaflets.

INTEGUMENTARY STUDIES IN THE POLYCARPICAE

SUMMARY The histogenetic development of the integuments of two representatives of the Magnoliaceae, Magnolia stellata and M. virginiana, was studied. The mode of development is the same in these two species. The two integuments have a different form of initiation: The inner integument (i.i.) is wholly of dermal derivation, whereas the primordium of the outer integument (o.i.) is formed as the result of cell divisions in the first subdermal cell layer. There is no apical initial or apical growth in either integument. The initials of the i.i. form rows of cells by repeated periclinal cell divisions, which rows develop independently in mutual juxtaposition to form a ring-shaped wall, the whole structure remaining meristematic. The i.i. is mainly three-layered, the o.i. is (in the younger stages at least) four-layered. The micropyle is formed by both integuments. The i.i. only becomes thicker by “secondary” cell divisions in the micropylar region. After fertilization appreciable changes take place in the o.i., the innermost cell layer forming the sclerotesta and the outer layers the vascularized sarcotesta.

On the First Lateral Root Primordium Formation Closer to Crown Root Apex of Rice Plants

In a crown root of rice plants (fig. 24), protophloem elements (PP) were the first of all vascular elements to show maturation usually at about 1 mm from the apex, and secondary wall layer starts covering protoxylem elements (PX) at a distance of 4-5 mm region from the apex. At about 7-8 mm from the apex, nuclei and cytoplasm in the protoxylem elements have degenerated and successively the secondary thickening ends. A first lateral primordium (I) of the crown root seems to originate in pericyclic cells between two protoxylems in which nuclei are degenerating and secondary thickening is going on. While covering by secondary wall in early metaxylem elements (MXI), anticlinal divisions of the first lateral root primordium (II) in the pericyclic cells begin to take place. Before and after periclinal division of the pericyclic cells of the first lateral root primordium, a certain grains (fig. 17 and 18, G) gather near the end wall as well as along protoplasmic membrane of metaphloem elements (fig. 24, MP) and a rounded shape of nucleolus in the metaphloem has changed to a chestnut-in-burs like shape (fig, 19) and the nucleolus is found near the sieve plate of the mature metaphloem as an extruded nucleolus. At a half-way penetration of the cortex (fig. 24, IV), secondary thickening of the early metaxylem completes and maturation of the metaphloem takes place. Before the first lateral root emerges on the surface of crown roots (V), late metaxylem elements (MXII) begin to be covered by secondary wall and all vascular elements except the late metaxylem have matured. A certain causal relation between the first lateral root primordium formation and the development of the vascular element, especially the protoxylem, may be estimated generally in any roots of rice plants.