Epidermal Cell Elongation Research Articles

Radial elongation of the epidermal cells of scutellum during caryopsis germination of wild oats (Avena fatua)

The radial elongation of epidermal cells of the scutellum of wild oat (Avena fatua L.) embryos was studied quantitatively. In the nondormant embryos, the length of these cells, both on the adaxial and abaxial sides of the scutellum, was doubled in 10 days after the beginning of the imbibition of caryopses in water; no such elongation of cells was observed in the dormant embryos. The epidermal cells elongated to form papillae only after the primary root had emerged from the caryopsis. The length of the entire scutellum and that of its epidermal cells increased significantly in the presence of gibberellic acid and glucose or sucrose. It is suggested that the epidermal cell elongation is a postgermination phenomenon involving absorption and transport of the products of starchy endosperm hydrolysis, thus promoting further growth in the germinated embryo of the wild oat.

The Roles of Plant Hormones in the Growth of the Corolla of Gaillardia grandiflora (Asteraceae) Ray Flowers

Corolla elongation and the roles of plant hormones in this process in Gaillardia grandiflora Van Houtte ray flowers were examined. The sterile ray flowers elongated during a 2-day period, and corolla growth was accompanied by fresh and dry weight increases and epidermal cell elongation (greatest near the base of the corolla) but not by cell division. Corollas excised from young ray flowers were measured during treatment in vitro with solutions of plant growth regulators. They elongated in response to gibberellins and fusicoccin but did not respond to auxins, cytokinins, abscisic acid, ethylene, or inhibitors of ethylene biosynthesis. Sequential and simultaneous hormone applications indicated no additive or synergistic effects between hormones, but auxin did reduce gibberellin-promoted growth. Analyses of endogenous auxins showed no significant variation, and ethylene production decreased prior to elongation, while a 20-fold increase in endogenous gibberellin activity was observed just prior to rapid corolla elongation. It appears that corolla growth in Gaillardia is accomplished by an increase in gibberellin activity alone, that multiple hormone interactions are not important in the control of corolla growth, and that part of the mode of action of gibberellin is acid-induced growth.

THE ROLES OF PLANT HORMONES IN THE GROWTH OF THE COROLLA OF GAILLARDIA GRANDIFLORA (ASTERACEAE) RAY FLOWERS

Corolla elongation and the roles of plant hormones in this process in Gaillardia grandiflora Van Houtte ray flowers were examined. The sterile ray flowers elongated during a 2‐day period, and corolla growth was accompanied by fresh and dry weight increases and epidermal cell elongation (greatest near the base of the corolla) but not by cell division. Corollas excised from young ray flowers were measured during treatment in vitro with solutions of plant growth regulators. They elongated in response to gibberellins and fusicoccin but did not respond to auxins, cytokinins, abscisic acid, ethylene, or inhibitors of ethylene biosynthesis. Sequential and simultaneous hormone applications indicated no additive or synergistic effects between hormones, but auxin did reduce gibberellin‐promoted growth. Analyses of endogenous auxins showed no significant variation, and ethylene production decreased prior to elongation, while a 20‐fold increase in endogenous gibberellin activity was observed just prior to rapid corolla elongation. It appears that corolla growth in Gaillardia is accomplished by an increase in gibberellin activity alone, that multiple hormone interactions are not important in the control of corolla growth, and that part of the mode of action of gibberellin is acid‐induced growth.

THE ROLES OF PLANT HORMONES IN STYLE AND STIGMA GROWTH IN GAILLARDIA GRANDIFLORA (ASTERACEAE)

Style and stigma elongation and stigma unfolding, and the roles of plant hormones in these processes in Gaillardia grandiflora Van Houtte were investigated. Style and stigma elongation in vivo began just after anthesis, and style elongation was accompanied by epidermal cell elongation (greatest near the stigma) and a fresh weight increase, but not by cell division or a dry weight increase. The stigma unfolded after the style and stigma elongated. Style‐stigma units excised from young disc flowers of this composite were measured as they responded to plant growth regulators applied singly, as well as in sequential and simultaneous combinations, in vitro. Style elongation was promoted by auxin, was inhibited by gibberellins and ethylene, and was unaffected by other growth regulators. Stigma elongation followed a similar pattern of response. Endogenous auxin levels and ethylene production showed parallel variation and endogenous gibberellin levels showed inverse variation with style and stigma elongation. Stigma unfolding was more sensitive to auxin applications and was promoted by applied ethylene. Ethylene production showed parallel variation and endogenous auxin levels showed inverse variation with stigma unfolding. AVG and Co2+ applications decreased auxin‐induced style elongation and fusicoccin promoted all of the growth responses of style‐stigma units in vitro. A gibberellin‐auxin‐ethylene‐acid growth interaction mode of control is proposed for these three growth processes.

Diploidy and chromosome endoreduplication in the development of epidermal cell lines in the first foliage leaf of durum wheat (Triticum durum Desf.)

The development of epidermal cell lines in the first foliage leaf ofTriticum durum was studied with a combined cytological and DNA cytophotometric analysis. It was shown that: (1) At emergence, the distal portion of the leaf is made of the cells pre-existing in the embryonic leaf and the mitotic activity is localized at the base of the leaf lamina (basal meristem). (2) The proliferating protoderm (outermost cell layer of the basal meristem) contains a meristematic cell population and a differentiating cell population. The cells produced by the protoderm differentiate with 2C, 4C, 8C, and 16 C nuclear DNA contents. (3) The endoreduplicated cells (EC) together with 4C cells form prominent cell rows in the leaf epidermis. The interstomatal cells (ISC) are all 2 C and the inter-hairs cells (IHC) are mostly 2 C (rare 4 C cells lie adjacent to the EC). (4) In the fully developed leaf, the frequency distribution of EC (8 C and 16 C) and 4C cells in a given epidermal segment (Fig. 1) corresponds to the frequency established in the epidermis differentiation zone (zone b, segment 1) at the time of development of that segment:e.g., segment 6 developed at 1–2 days after seed germination, segment 5 at 3 days after germination and so on. (5) Epidermal cell elongation starts in segment 1 and reachs its maximum in the older leaf segments, 5 and 6. The rate of cell elongation is independent of nuclear DNA content; chromosome endoreduplication precedes elongation. (6) The possibility of using epidermal cell parameters in studies on first leaf growth inT. durum is discussed.

Thigmomorphogenesis: Changes in Cell Division and Elongation in the Internodes of Mechanically-perturbed or Ethrel-treated Bean Plants*

Examination of first internodes of young Phaseolus vulgaris L. plants which have been subjected to mechanical perturbation shows decreased elongation and increased radial growth. The decreased elongation can be attributed to both reduced cell elongation of epidermal and cortical cells and a reduced number of cells in the vascular and pith tissues. The increased radial enlargement is due to increased cortical cell expansion and increased secondary xylem production resulting from increased cambial activity. All of these responses are observable within a few hours of a single mechanical perturbation. Treatment of plants with ethrel mimics all of these effects of mechanical perturbation.

Growth and Form in Nematodes: Iv. Tail Length and Vulva Position

During post-embryonic growth tail length can increase, remain constant or even decrease. Usually, such changes cannot be explained as populations of the same species may behave differently. The differences in length between males and females is based, I suggest, on the mechanics of mating and on requirements for defaecation. The constant position of the vulva is probably not essential functionally but may arise from the cell-constancy of the nematodes and equal elongation of epidermal cells in front of and behind the vulva. The position of the vulva is usually expressed as a percentage of the entire body length but, in several long tailed tylenchs, it is better to calculate it as a percentage of the distance between the top of the head and the anus.

Role of monoamine metabolism in wing dimorphism of the aphid Myzus persicae

1. 1. Wing dimorphism of the aphid Myzus persicae which normally is regulated by a number of exogenic factors can be influenced by neuropharmaca. 2. 2. With micro-injections of drugs that are known to act on monoamine metabolism it is possible to direct the course of development towards the alate or apterous morph. 3. 3. Serotonergic activity inhibits elongation of epidermal wing bud cells; this effect is antagonized by adrenergic compounds. 4. 4. The effects of the drugs tested suggest that factors in the “milieu interieur” regulating differentiation of the wing bud are mediated by neurotransmitters.

Effect of gibberellins on growth of pea seedling internode

Elongation of internode segments of dwarf pea seedlings excised 4 mm below the plumular hook was stimulated by GA 3 but not by GA 1 or GA 5. However, all three gibberellins induced cell elongation in the region from which this segment was isolated on application to intact seedlings. It is concluded that GA 1 and GA 5 are converted to a GA 3-like hormone. Measurement of epidermal cell elongation in the epicotyl further indicates that GA 3 or a GA 3-like hormone may be the functional form of the hormone required for cell elongation.

Electron Microscopy of the Developing Cotton Fiber

Cotton fibers are single cells that arise by virtue of elongation of certain cells in the outer epidermal layer of the outer integument of the cottonseed. Guard cells are present in this epidermal layer of the cottonseed, but the majority of the cells are cuboidal in nature (Fig. A). These cuboidal cells either elongate to become lint fibers or fuzz fibers or fail to elongate and simply remain as epidermal cells. Initiation of elongation of epidermal cells that ultimately become lint fibers occurs at anthesis. The mature lint fiber is a single cell having a diameter of some 20 micra and which is frequently over an inch in length.

EMASCULATION EFFECTS ON THE STAMEN FILAMENT OF NIGELLA HTSPANICA AND THEIR PARTIAL REVERSAL BY GIBBERELLIC ACID

Anther removal from stamens whose filaments are 1–3 mm long restricts filament elongation to approximately 60% of the normal length. Removal of one‐third to one‐half of the anthers affects only the antherless filaments and does not appear to inhibit the growth of the other organs of the flower. Filament growth inhibition induced by anther removal involves both an inhibition of epidermal cell elongation along the length of the filament and also an inhibition of cell division. There is no evidence that the inhibition of filament growth is a response to damage caused by anther removal. Rather, it is suggested that anther removal severs a normal hormonal relationship existing between the anther and the developing filament. The application of gibberellic acid (GA3) in lanolin paste stimulated the elongation of the antherless filaments to achieve an average of 87% of the filament length of adjacent intact stamens. The closer a filament is to having attained its final number of cells before anther removal, the closer does its length come to reaching the final length of filaments in intact stamens. The elongation of these antherless filaments with the application of GA3 was accompanied by elongation of the epidermal cells of the filament to normal, or in some cases greater than normal, lengths. There is no evidence that GA3 application affected the inhibition of epidermal cell devision induced by anther removal. The results of this study support the suggestion of Plack that emasculation‐induced inhibition in the growth of floral organs and its reversal by GA3 is a general phenomenon.

Emasculation Effects on the Stamen Filament of Nigella hispanica and Their Partial Reversal by Gibberellic Acid

Anther removal from stamens whose filaments are 1–3 mm long restricts filament elongation to approximately 60% of the normal length. Removal of one-third to one-half of the anthers affects only the antherless filaments and does not appear to inhibit the growth of the other organs of the flower. Filament growth inhibition induced by anther removal involves both an inhibition of epidermal cell elongation along the length of the filament and also an inhibition of cell division. There is no evidence that the inhibition of filament growth is a response to damage caused by anther removal. Rather, it is suggested that anther removal severs a normal hormonal relationship existing between the anther and the developing filament. The application of gibberellic acid (GA3) in lanolin paste stimulated the elongation of the antherless filaments to achieve an average of 87% of the filament length of adjacent intact stamens. The closer a filament is to having attained its final number of cells before anther removal, the closer does its length come to reaching the final length of filaments in intact stamens. The elongation of these antherless filaments with the application of GA3 was accompanied by elongation of the epidermal cells of the filament to normal, or in some cases greater than normal, lengths. There is no evidence that GA3 application affected the inhibition of epidermal cell devision induced by anther removal. The results of this study support the suggestion of Plack that emasculation-induced inhibition in the growth of floral organs and its reversal by GA3 is a general phenomenon.

The structure of eucalypt mycorrhizas

All Eucalyptus species examined are capable of forming ectotrophic mycorrhizas in association with suitable fungi. The phenomenon is widespread but the intensity of infection varies according to the environment in which they occur, mycorrhizas being most common in leached soils which accumulate organlc materlal in or above the surface layers. The general structure and behaviour of these infected roots is similar to that described for Fagus sylvatica. Eucalypt mycorrhizas are compared with ontogenetically equivalent uninfected rootlets, revealing differences in anatomical structure which are assigned to two categories. These are quantitative differences in which certain aspects of mycorrhizal structure differ from the typical structure found in uninfected roots yet approximate to certain extreme expressions of uninfected root anatomy, and qualitative differences where infected and uninfected roots possess quite distinct characteristics. In the former category, suppression of root hair formation and reduction of meristematic and root cap tissues in mycorrhizal axes appear to be generalized changes of the kind which result from slow growth through an unfavourable environment, so that it is not clear whether the invading fungus induces or merely perpetuates the state found in mycorrhizas. In the latter category, radial elongation of epidermal cells and pronounced thickening of cell walls in the inner cortex are shown to be specific changes induced only by fungal infection. Mycorrhizal morphology may be simulated by uninfected roots treated with high concentrations of naphthaleneacetic acid. Such treatment also induces some generalized anatomical changes similar to those found in mycorrhizas, but fails to bring about the specific changes characteristic of fungal infection. The importance of applying anatomical criteria to studies on morphogenic compounds is discussed.

The Effect of Gibberellin and Phenylboric Acid on Xylem Differentiation and Epidermal Cell Elongation in Bean Roots

The Effect of Gibberellin and Phenylboric Acid on Xylem Differentiation and Epidermal Cell Elongation in Bean Roots

Studies on the Effects of Some Organic Acids on the Root Hair Formation in the Root of Rice Plants.

It was found by the authors that the root hair formation and their growth in rice roots are accelerated when the water percolates vertically in the paddy soils, and was thought that certain substances responsible for regulating the root hair development are derived from the compost under the irrigated condition, and they are probably eliminated from the paddy soils by water-percolation (KAWATA and ISHIHARA, 1961 a). The present experiment was carried on to find the morphogenetical effects of some organic acids (formic, acetic and butyric acid) on the development of the root hairs and epidermal cells of the roots by using the ordinary or aseptic water culture method. The following results were obtained. When the concentration of acetic acid was kept between 2.5 mmol and 5.0 mmol., which is known to be frequently found in the paddy soils, it inhibited the root hair formation and their growth to a great extent, but it did not affect the root and epidermal cell elongation so much. This morphological appearance of epidermis of the root treated with acetic acid was similar to that of the rice plants grown in the non water-percolated soils. Formic acid (2.5 mmol. and 5.0 mmol.) and butyric acid (2.5 mmol. and 0.50 mmol.) retarded not only the root hair formation and their growth, but also the root and epidermal cell elongation. From these results, especially in the case of the acetic acid, our hypothesis mentioned above seems to be true. As reported in the previous paper (KAWATA and ISHIHARA, 1961 b) the ribonucleic acid, the metabolism of which is closely related to the process of the potassium absorption in rice roots, was found to exist in the root hairs for a long time. It is suggested, on the basis of these facts, that the development of the rice plants in the paddy fields is affected because of the accumulation of these organic acids in the soils, which control the absorption of nutrients.