Epidermal Hair Research Articles

Phytophthora resistance in cacao (Theobroma cacao): Influence of pod morphological characteristics

Twelve diverse cacao (Theobroma cacao) genotypes were assessed for pod resistance to Phytophthora palmivora at the penetration and post‐penetration stages of infection using two inoculation methods. Correlation analysis between a number of pod characteristics (stomatal frequency, stomatal pore length, surface wax, thickness of exocarp/endocarp, hardness of exocarp/mesocarp, moisture content) and resistance indicated a strong relationship between resistance to lesion establishment (lesion frequency) and the joint effect of stomatal frequency and pore length. The epidermal impressions of the pod surfaces bearing germinating zoospores of P. palmivora provided evidence that penetration occurs through stomata, epidermal hair base, scar and by direct penetration. A poor correlation was obtained between the pod characteristics studied and post‐penetration resistance, suggesting that this resistance, assessed by lesion size, is not governed by morphological or physical characteristics of the pod, but probably by biochemical factors. The importance of these findings in breeding of cacao for resistance to P. palmivora is discussed.

Changes in Epicuticular Flavonoids and Photosynthetic Pigments as a Plant Response to UV-B Radiation

Treatment of Gnaphalium vira-vira plants with UV-B radiation caused changes in plant growth and in plant chemistry. The leaf surface contained two O-methylated flavones, araneol and 7-O-methylaraneol. HPLC analysis showed that 20 days of UV-B radiation increased the synthesis of 7-O-methylaraneol at the expense of araneol. Spectrophotometric analysis of the photosynthetic pigments showed that UV-B radiation also increases the pigment content in treated plants. Another U V alteration is epidermal hair damage, as observed in SEM pictures of treated leaves. This combination of physiological and phytochemical effects may be interpreted as a plant response to UV-B stress

Anatomically preserved Permian Noeggerathiopsis leaves from east Antarctica

Permineralized Noeggerathiopsis leaves from the Permian Bainmedart Coal Measures of eastern Antarctica are characterized by prominent abaxial stomatiferous furrows protected by dense epidermal hairs. The leaves lack fibre bundles characteristic of Euramerian cordaitaleans, but are similar to late Palaeozoic Angaran cordaite leaves of the genus Rufloria. Other leaf morphological characters suggest a possible close relationship between Noeggerathiopsis and glossopterids. The striking similarity between the morphology and anatomy of Angaran and Gondwanan cordaites and several other plant groups suggests that not all of these features are convergent, and that some floristic interchange between these opposing high-latitude provinces may have occurred during the late Palaeozoic. The strong stomatal protection in Noeggerathiopsis leaves preserved in high-latitude, paludal deposits suggests that these structural features are not strictly xeromorphic in function.

The control of trichome spacing and number in Arabidopsis

Arabidopsis trichomes are single-celled epidermal hairs that serve as a useful model for the study of plant cell differentiation. An examination of the distribution of trichomes early in their development revealed that developing trichomes occur adjacent to another trichome much less frequently than would be expected by chance. Clonal analysis of epidermal cell lineages ruled out a role for cell lineage in generating the observed minimum-distance spacing pattern. Taken together, these results are consistent with a role for lateral inhibition in the control of trichome development. We also report the identification of a new locus, Reduced Trichome Number (RTN), which affects the initiation of trichomes. This locus was initially detected by the reduced number of leaf trichomes on Landsberg erecta plants compared to that on Columbia plants. Quantitative Trait Locus mapping revealed that more than 73% of the variation in trichome number was due to a major locus near erecta on chromosome 2. The reduced number of trichomes conditioned by the Landsberg erecta allele of this locus appeared to be due to an early cessation of trichome initiation. The implications of these observations are discussed with regard to previously published models of trichome development.

An analysis of the early floral development of Pittosporum tobira (THUNB.) AITON and some remarks on the systematic position of the family Pittosporaceae

AbstractIn Pittosporum tobira all floral organs are initiated in a strictly acropetal succession. It is striking that sepals and petals show an extremely early hyponastical development. Important floral characters for placing the family Pittosporaceae near the Apiales (Araliaceae and Apiaceae) are the early sympetaly, only gradual differences in the gynoecium development and placentation, and the fact that a nectar secreting area is situated at the base of the dorsal carpel flanks (ovary superior in Pittosporaceae, inferior in Apiales).Viscid latex, which plays an important role in the dispersal of the seeds by exozoochory, is produced by the multicellular epidermal hairs in the septal (placental) region.

Gibberellins Promote Vegetative Phase Change and Reproductive Maturity in Maize

Postembryonic shoot development in maize (Zea mays L.) is divided into a juvenile vegetative phase, an adult vegetative phase, and a reproductive phase that differ in the expression of many morphological traits. A reduction in the endogenous levels of bioactive gibberellins (GAs) conditioned by any one of the dwarf1, dwarf3, dwarf5, or anther ear1 mutations in maize delays the transition from juvenile vegetative to adult vegetative development and from adult vegetative to reproductive development. Mutant plants cease producing juvenile traits (e.g. epicuticular wax) and begin producing adult traits (e.g. epidermal hairs) later than wild-type plants. They also cease producing leaves and begin producing reproductive structures later than wild-type plants. These mutations greatly enhance most aspects of the phenotype of Teopod1 and Teopod2, suggesting that GAs suppress part but not all of the Teopod phenotype. Application of GA<inf>3</inf> to Teopod2 mutants and Teopod1, dwarf3 double mutants confirms this result. We conclude that GAs act in conjunction with several other factors to promote both vegetative and reproductive maturation but affect different developmental phases unequally. Furthermore, the GAs that regulate vegetative and reproductive maturation, like those responsible for stem elongation, are downstream of GA<inf>20</inf> in the GA biosynthetic pathway.

The use of soft x rays to study the ultrastructure of living biological material

Imaging biological specimens with soft x rays offers several potential benefits over electron microscopy, and these are briefly reviewed. The disadvantages, most notably radiation-induced structural changes, have been investigated and images of irradiated algal cells ( Chlorella ) are presented. In soft x-ray contact microscopy the image is recorded rapidly to avoid both natural and radiation-induced movement and this technique has been used to study the ultrastructural effects of electron microscopy fixatives. In the epidermal hairs of tomato plants there are numerous strands of cytoplasm which, by light microscopy, appear to traverse the vacuole but are rarely seen by electron microscopy. However, by soft x-ray contact microscopy these strands and the organelles within them can be successfully imaged. Moreover, examination by soft x-ray contact microscopy of the cytoplasm in a fixed material shows that these strands are not present in chemically fixed material. This paper also reports the use of soft x-ray contact microscopy to examine the abscission cells found within the protonema of a moss ( Bryum tenuisetum ) and compares the images to those obtained by light and electron microscopy.

Graft chimeras and somatic hybrids for new cultivars

Abstract Three techniques were evaluated as methods for plant improvement: protoplast fusion in vitro for somatic hybrids, protoplast co-culture in vitro for chimeras, and graft manipulation in planta for periclinal chimeras. Methods were developed initially for herbaceous, solanaceous species and then evaluated on two species of woody Actinidia. Protoplasts from tomato (2n = 24) and Bü (a Solanum hybrid obtained by fusing nightshade and dihaploid potato protoplasts, 2n = 96) were fused at laboratories located at Kiel, Germany, and Levin, New Zealand. Identical methods were used at each laboratory, and plants were regenerated from the hybrid callus. At Kiel, only 1.6% of the regenerants were symmetric fusions that contained 120 chromo somes. One chimeric plant remained genomically stable during 3 years of in vitro growth and a further year in the glasshouse. At Levin, 83% of regenerants were asymmetric fusions with additional nightshade or Bii genomes. Some regenerants, however, contained a single nightshade genome. Protoplasts from Actinidia were fused using the methods detailed for the solanaceous plants, but regeneration of plants was not achieved. Chimeric plants were obtained by co-culturing Bü and tomato plants. At Kiel, 2.1% of the regenerants were chimeric. Co-cultures of protoplasts between Actinidia arguta and A. deliciosa, at Levin, did not produce regenerative callus. Periclinal chimeras were sought from in planta grafts between tomato and nightshade. Two chimeric shoots were obtained. On the basis of epidermal hair type, pollen compatibility, seed and fruit set, one chimera had the histogenic LI layer of nightshade over LII and LIII histogenic layers of tomato (NTT), and the other had two layers of nightshade over one layer of tomato (NNT). Chimera NTT was more stable than NNT, but both produced axillary shoots with characteristics of the other chimera. Periclinal chimeras were also sought from graft unions in planta and in vitro between A. arguta and A. deliciosa. From in planta grafts, all adventitious shoots were A. arguta. From in vitro grafts, 75% of the shoots that regenerated were A. deliciosa and none was chimeric. Each of these techniques has the potential to produce new plants. However, the probability of success was low and therefore a large number of regenerants would be required from which to select the desired plants.

The Use of Soft X Rays to Study the Ultrastructure of Living Biological Material

Imaging biological specimens with soft x rays offers several potential benefits over electron microscopy, and these are briefly reviewed. The disadvantages, most notably radiation-induced structural changes, have been investigated and images of irradiated algal cells (Chlorella) are presented. In soft x-ray contact microscopy the image is recorded rapidly to avoid both natural and radiation-induced movement and this technique has been used to study the ultrastructural effects of electron microscopy fixatives. In the epidermal hairs of tomato plants there are numerous strands of cytoplasm which, by light microscopy, appear to traverse the vacuole but are rarely seen by electron microscopy. However, by soft x-ray contact microscopy these strands and the organelles within them can be successfully imaged. Moreover, examination by soft x-ray contact microscopy of the cytoplasm in a fixed material shows that these strands are not present in chemically fixed material. This paper also reports the use of soft x-ray contact microscopy to examine the abscission cells found within the protonema of a moss (Bryum tenuisetum) and compares the images to those obtained by light and electron microscopy.

Epidermal Cell Fate Determination in Arabidopsis : Patterns Defined by a Steroid-Inducible Regulator

The Arabidopsis mutant ttg lacks both trichomes (epidermal hairs) and anthocyanin pigments. Trichomes and anthocyanins are restored by the constitutive expression of the maize transcriptional regulator (R). The expression of an R-glucocorticoid receptor chimeric protein results in a steroid hormone-dependent, conditional allele of R that functions in whole Arabidopsis plants. The response of the chimeric protein to pulses of hormone was used to define the pattern and timing of trichome formation on the developing leaf epidermis. Each adaxial epidermal leaf cell appears to have an equal probability of differentiating into a trichome; there is a temporal zone of decision for trichome cell fate that proceeds as a wave from the tip to the base of developing leaves.

Roles of the GLABROUS1 and TRANSPARENT TESTA GLABRA Genes in Arabidopsis Trichome Development.

Arabidopsis trichomes are branched, single-celled epidermal hairs. These specialized cells provide a convenient model for investigating the specification of cell fate in plants. Two key genes regulating the initiation of trichome development are GLABROUS1 (GL1) and TRANSPARENT TESTA GLABRA (TTG). GL1 is a member of the myb gene family. The maize R gene, which can functionally complement the Arabidopsis ttg mutation, encodes a basic helix-loop-helix protein. We used constitutively expressed copies of the GL1 and R genes to test hypotheses about the roles of GL1 and TTG in trichome development. The results support the hypothesis that TTG and GL1 cooperate at the same point in the trichome developmental pathway. Furthermore, the constitutive expression of both GL1 and R in the same plant caused trichomes to develop on all shoot epidermal surfaces. Results were also obtained indicating that TTG plays an additional role in inhibiting neighboring cells from becoming trichomes.

Heterochronic effects of glossy15 mutations on epidermal cell identity in maize.

Vegetative development in maize is divided into a juvenile phase and an adult phase that differ in the expression of a large number of morphological, anatomical, and biochemical traits. Recessive mutations of Glossy15 cause a premature switch in the expression of some of these phase-specific traits. Mutant plants cease producing juvenile traits (e.g. epicuticular wax) and begin to produce adult traits (e.g. epidermal hairs) significantly earlier than their wild-type siblings. In glossy15-1 plants this switch generally occurs at leaf 2 or 3 rather than at the normal position of leaf 6 or 7. An analysis of the effect of glossy15 mutations on a variety of vegetative and reproductive traits revealed that these mutations only affect the character of the epidermis. They have no effect on the overall vegetative morphology of the plant, or on its reproductive development. This phenotype is the opposite of that of the gain-of-function mutations Teopod1, Teopod2 and Teopod3, all of which prolong the expression of a large number of juvenile traits. Double mutants between glossy15 and Teopod1 or Teopod2 indicate that Glossy15 is required for the effect of Teopod1 and Teopod2 on epidermal traits but not for other aspects of the Teopod phenotype. We conclude that Glossy15 initiates or maintains the expression of juvenile epidermal traits and suppresses the expression of adult epidermal traits, and that it acts downstream of the Teopod genes.

Retinoic Acid and Mouse Skin Morphogenesis. I. Expression Pattern of Retinoic Acid Receptor Genes During Hair Vibrissa Follicle, Plantar, and Nasal Gland Development

The spatial and temporal expression of the nuclear retinoic acid receptors alpha, beta, and gamma (RAR-alpha, beta, and gamma) was compared by in situ hybridization during hair vibrissa follicle and nasal and plantar eccrine gland morphogenesis in mouse embryo. The RAR-alpha and RAR-gamma transcripts are abundant in the dermal papilla cells of the hair vibrissa when these cells elicit epidermal hair placode (12.5-d embryos) and hair follicle (13.5-d embryos) formation. Both these transcripts are also abundant in the dermal cells of the plantar foot pad at the initiation stage (17.5-d embryos) of glandular morphogenesis. In epidermal cells, the distribution of RAR-gamma transcripts increases in parallel with hair vibrissa follicle and sweat gland differentiation, and thus may be part of the epidermal response to the dermal instructions. The RAR-beta signal is barely above control level during both hair vibrissa and plantar gland morphogenesis. By contrast, during nasal gland formation (12.5- to 15.5-d embryos), the RAR-beta signal reaches a high level in mesenchymal cells, whereas the RAR-alpha-transcripts are present in both epithelial and mesenchymal cells. These results suggest a role for RAR-alpha and RAR-gamma in the epidermal-dermal interactions that lead to hair follicle and plantar gland morphogenesis, whereas the nasal gland development implies RAR-alpha and RAR-beta gene expression. This should be correlated with the expression of the RAR-beta gene that was previously shown to be linked to the RA-induced glandular metaplasia of hair vibrissa follicles.

Epidermal studies of some species of family Solanaceae used in traditional medicine in West Africa

AbstractLeaf epidermal structure and developmental pattern of the stomatal complex of 30 species of the family Solanaceae are described. Epidermal cells of almost all the species showed wall sinuousity. However, in Brunfelsia uniflora and some species of the genus Solanum viz. S. aethiopicum, S. dasyphyllum, S. macrocarpon and S. verbascifolium the cells were straight‐walled. Several types of epidermal hairs were observed on both the upper and lower epidermis. They include bicellular eglandular, multicellular stellate and club‐shaped hairs. The leaves of most species were amphistomatic; however, a few species with hypostomatic leaves were also encountered. Mature stomata were either anomocytic or anisocytic with hemimesogeneous developmental pattern. In Schwenkia americana, however, mature stomata were diacytic with eumesogenous developmental pathway. Interspecific variation observed in the distribution, size and frequency of stomata may prove useful in the authentication of the foliar materials of these plants when used as crude drugs.

Sub-cellular distribution of nitrogen compounds inAzolla andAnabaena by ESI and EELS analysis

The sub-cellular localization of some nitrogen compounds within the leaf cavities ofAzolla filiculoides Lam. was obtained by means of electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS). The analyses were performed on ultrathin unstained sections of differentAzolla leaf cavities which contain epidermal hairs,Anabaena azollae Strasb. and bacteria. Net nitrogen distributions were visualized by image analysis, and nitrogen peaks were evidenced in spectra recorded in the same areas. Different distributions of nitrogen compounds were observed within the leaf cavities along the stem, in particular inside the epidermal hairs ofAzolla and the vegetative cells and heterocysts ofA. azollae.

613 (PS 3) SUCROSE SYNTHASE LOCALIZATION DURING SEED AND HAIR DEVELOPMENT: COTTON OVULES AS A MODEL SYSTEM

Immunolocalization of sucrose synthase in cotton ovules was conducted to clarify the relationship between this enzyme and sucrose import during seed and hair development. Although rapidly growing plant organs are known to have high activities of sucrose synthase, information on specific localization has been minimal at the cell level. Cotton ovules were examined in the present work as representatives of developing dicot seeds, and because their expanding hairs would have a locally high demand for cell wall synthesis. Initial analyses focused on ovules immediately before and after anthesis/pollination. Heavy immunolabel was observed solely in the nucellar tissue 1 day before anthesis. Immediately following anthesis/pollination, however, sucrose synthase became evident in cells of the external (but not internal) integument, expanding from the chalazal to micropylar end of this tissue. Little sucrose synthase was directly associated with very young epidermal hairs prior to their most rapid expansion. Immunolabel appeared to be localized in cells associated with the vascular bundle of this external integument. The shift in spatial/temporal localization of sucrose synthase in cotton ovules following pollination indicates a close association between sucrose synthase and probable sites of sucrose import at a cellular level during early seed development.

Species of the Cretaceous Tree Fern Tempskya from Utah

Nine species of the permineralized stems of Tempskya were investigated from the upper Lower Cretaceous Cedar Mountain and Burro Canyon Formations, and the lower Upper Cretaceous Dakota Formation in central and southeastern Utah. Tempskya jonesii, T. stichkae, and T. readii are new and are differentiated on the basis of the radial orientation of their dorsiventral stems, their internodal lengths, the lack of sclerenchyma in the inner cortex of T. jonesii, the three nearly continuous zones of sclerenchyma in the inner cortex of T. stichkae, and the completely sclerotic inner cortex of T. readii. Specimens of T. jonesii and T. minor were collected in growth position near Castle Dale, Utah, which is the first time Tempskya has been collected in this position in North America. Thin leaves were also observed for the first time in Tempskya in specimens of T. wyomingense. Tunnels containing three sizes of fecal pellets are common in tissues of stems, roots, petioles, and epidermal hairs of the false trunks of Tem...

Purification of 4S-limonene synthase, a monoterpene cyclase from the glandular trichomes of peppermint (Mentha x piperita) and spearmint (Mentha spicata).

The p-menthane monoterpenes of the Mentha species are biosynthesized from geranyl pyrophosphate via the monocyclic olefin 4S-limonene. A monoterpene cyclase was isolated from both Mentha x piperita (peppermint) and Mentha spicata (spearmint) that catalyzes the cyclization of geranyl pyrophosphate to 4S-limonene. This enzyme, 4S-limonene synthase, was purified to apparent homogeneity by dye ligand, anion exchange, and hydrophobic interaction chromatography. Since the monoterpenes of Mentha are synthesized and secreted in modified epidermal hairs called glandular trichomes, an extract of isolated glandular trichome cells was used as the source of this enzyme. A combination of gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that purified 4S-limonene synthase had a native molecular weight of 56,000 and was monomeric. The principal product of the enzyme was enantiomerically pure (-)-4S-limonene, and a catalytic constant of 0.3/s was determined. The basic properties of 4S-limonene synthase from both M. x piperita and M. spicata are identical and, in general, are similar to those of other monoterpene, sesquiterpene, and diterpene cyclases isolated from microorganisms and higher plants.

Some leaf structures related to salt regulation in kallar grass[Leptochloa fusca(L.) kunth

Abstract The Kallar grass leaf is linear with spiny surfaces. On its margins were found spines with a broad base, and on the upper and the lower surface, vesicles or swollen epidermal hairs with pointed, capped ends. On cellulose‐acetate film moistened with acetone and pressed against the leaf surface, the vesicles appeared as bladder‐like structures located above the epidermis. More vesicles were found on the upper than on the lower surface. In young field plants, the vesicles of the sheath were less developed and fewer in number than those of the blade. Vesicles in the leaf sheath were found largely on the lower (outer) surface. Using a pressure probe, he vesicles were found to contain sap and a turgor pressure of about 0.3 MPa which decreased with 100 mM NaCl and 10 mM PEG 6000. The sheath cells which were chlorophyllous, larger and rectangular, had a turgor pressure of about 0.1 MPa, which was either little affected or was increased when the leaf sheath was exposed to 100 mM NaCl or PEG 6000. The impo...

Two new fossil matoniaceous stem genera from Tasmania, Australia

Two new genera, Tasmanopteris and Heweria, from Tasmania are the first definite permineralized rhizomes assignable to the Matoniaceae. Tasmanopteris richmondii sp. nov., of mide-Mesozoic age, is from the Lune River site in southwestern Tasmania and is composed of four or more annular solenostelos separated by cortices with an inner mesarch xylem ring and outer exarch xylem rings. Secretory canals occur in the cortices between the protoxylem clusters of its outer xylem rings. The specimen of Heweria kempii sp. nov., which is very similar to extant Matonia, was collected from a Lower Tertiary conglomerate in central Tasmania but was reworked from older sediments. Anatomically, the rhizomes of Heweria consist of 3–6 annular solenosteles with the inner and middle xylem rings being mesarch, whereas the outer ring is exarch. Roots arise opposite the protoxylem clusters of the outermost ring. Epidermal hairs on the stems of this genus are like those of living Matonia in being attenuate, uniseriate, and multicellular. Associated venation pattern of partially preserved leaves, isolated sporangia, annuli, and spores in this specimen provide additional support for the relationships of this fossil to modern Matonia.