Parenchyma Cells Of Cortex Research Articles

Pharmacognostical Study of Bark of Shimshapa (Dalbergia sissoo Roxb)

Purpose: Pharmacognostical evaluation of bark of Dalbergia sissoo is done for identification in field and differentiates from other species of Dalbergia. Methods: Drug is studied taxonomically and its macroscopic, microscopic features were studied including powder microscopy of bark with suitable instruments. Results: Macroscopic study reveals on drying bark is flat curved inward with presence of cracks color reddish brown outer surface rough warty while inner surface was tough, longitudinally striated whereas microscopic study reveals outline of transverse section (TS) exposed rhytidome covering the upper part of section. It was continue with cork cells followed wide zone of secondarycortex. Concentric rings of fibres were present throughout the secondary phloem. The detailed TS showed dark coloured rhytodome cells followed by multilayered cork cells. Secretory cells containing tannin was present in secondary cortex zone. Presence of calcium oxalate crystals present in rays cells and parenchyma cells of cortex. Starch grains were present throughout the parenchyma cells. Powder was dark red in colour, bitter .taste , fruity odor. Powder microscopy reveals fragments of cork cells, stone cells, septate fibres, Pitted medullary ray cells, Prismatic crystals of calcium oxalate, simple starch grains and fragments of fibres found present. Conclusion: Finding of this study will falicitate pharmacognostic standardization of plant material and become an aid for identification as well as preparation of herbal monographs for the species and to enjoy the Ayuvedic classical claims.

GhAPC8 regulates leaf blade angle by modulating multiple hormones in cotton (Gossypium hirsutum L.)

Leaf angle, including leaf petiole angle (LPA) and leaf blade angle (LBA), is an important trait affecting plant architecture. Anaphase-promoting complex/cyclosome (APC/C) genes play a vital role in plant growth and development, including regulation of leaf angle. Here, we identified and characterized the APC genes in Upland cotton (G. hirsutum L.) with a focus on GhAPC8, a homolog of soybean GmILPA1 involved in regulation of LPA. We showed that independently silencing the At or Dt sub-genome homoeolog of GhAPC8 using virus-induced gene silencing reduced plant height and LBA, and that reduction of LBA could be caused by uneven growth of cortex parenchyma cells on the adaxial and abaxial sides of the junction between leaf blade and leaf petiole. The junction between leaf blade and leaf petiole of the GhAPC8-silenced plants had an elevated level of brassinosteroid (BR) and a decreased levels of auxin and gibberellin. Consistently, comparative transcriptome analysis found that silencing GhAPC8 activated genes of the BR biosynthesis and signaling pathways as well as genes related to ubiquitin-mediated proteolysis. Weighted gene co-expression network analysis (WGCNA) identified gene modules significantly associated with plant height and LBA, and candidate genes bridging GhAPC8, the pathways of BR biosynthesis and signaling and ubiquitin-mediated proteolysis. These results demonstrated a role of GhAPC8 in regulating LBA, likely achieved by modulating the accumulation and signaling of multiple phytohormones.

Morpho-anatomical and physiological characteristics responses of a paried near-isogenic lines of waxy corn to waterlogging

Waterlogging stress is one of the most natural stress, which due to excessive rainfall or low-lying terrain, and limits crop growth and yield. Our objective was to study the morpho-anatomical and physiological characteristics of a paired near-isogenic lines of waxy corn under waterlogging stress. This experiment was implemented in pots with a paired of near-isogenic lines differing in waterlogging tolerance: Zz-R (waterlogging-resistant) and Zz-S (waterlogging-sensitive). Root morphology features, anaerobic respiratory enzyme activity, and tissue anatomical characteristics were measured at 0, 2, 4, 6 and 8d in the control and waterlogging conditions. The result indicated that waterlogging induced a decrease in the root length, volume and surface areas of the two waxy corn inbred lines, the total root length, root volume, and root surface area of the Zz-R showed less reduction than the Zz-S. Waterlogging stress influenced significantly by the parenchyma cells in cortex of root between Zz-R and Zz-S. Zz-R can also maintain a higher level of anaerobic respiratory enzyme activity under waterlogging stress. The different reaction between the paired near-isogenic lines may be responsible for higher tolerance of Zz-R than Zz-S. These results can provide a certain theoretical basis of the resistance evaluation and breeding to the resistant varieties.

The Damage of Root, Leaf and Chloroplast Ultrastructure on Maize Seedlings Caused by Salinity Stress

Salinity is one of major problems in agriculture especially in arid and semiarid area that causes the damage of many aspects in plant growth and development. This study observed root, leaf and chloroplast ultrastructure as well as nutrient uptake in maize plants exposed to salinity stress. Maize seedlings were treated with 0, 1, 2 and 3% NaCl for 5 days and placed in the growth chamber. Root, leaf, and chloroplast ultrastructure were observed by using SEM and TEM. Nutrient uptake was estimated from the content of trace elements of leaves that quantified by using ICP-MS, except chlorine by an atomic absorption flame spectrometer. The results showed that salinity slightly damaged roots anatomy. Epidermis and parenchyma cells of cortex and pith were shrinkage in 2 and 3% NaCl-treated plants. Leaf anatomy observation showed mesophyll and bundle sheath cells slightly suppressed. Chloroplasts content inside those cells were dramatically decreased. Ultrastructure observation showed the damage of chloroplasts inside mesophyll cells. Anatomical and ultrastructural damage of roots, leaves, and chloroplasts was accompanied by altering uptake of some trace elements. The contents of aluminum, calcium, iron, magnesium, sodium, chlorine, in NaCl-treated plants, were higher than control. Otherwise, boron, potassium, and phosphor were lower.

Salinity Stress Alters Nutrient Uptake and Causes the Damage of Root and Leaf Anatomy in Maize

<p class="Els-Abstract-text">Salinity is one of major problems in agriculture especially in arid and semiarid area due to causes the damage of many aspects in plant growth and development. This study observed root and leaf anatomy and nutrient uptake in maize plants exposed to salinity stress. Maize seedlings were placed in the plantation room under same temperature, humidity and light intensity conditions and were treated with 0 %, 1 %, 2 % and 3 % NaCl for 5 d. Anatomy of root and leaf were observed using scanning electron microscopy (SEM). Nutrient uptake was estimated by the content of trace elements of leaves. Trace element were quantified using inductively coupled plasma-mass spectrometry (ICP-MS), but chlorine was determined by an atomic absorption flame spectrometer. The results showed that salinity slightly damaged roots anatomy. Epidermis cells and parenchyma cells of cortex and pith were shrinkage in 2 % and 3 % NaCl-treated plants. Leaf anatomy showed mesophyll and bundle sheath cells which slightly suppressed. Meanwhile, chloroplasts content inside those cells were dramatically decreased. Anatomical damage of roots and leaves was accompanied by altering uptake of some trace elements. The contents of aluminum, calcium, iron, magnesium, sodium, chlorine, in NaCl-treated plants were higher than control. Otherwise, boron, potassium and phosphor were lower in NaCl-reated plants. The rest of trace elements were in comparable concentration.</p><p> </p><p><strong>Keywords:</strong> maize; leaf; nutrient; root; salinity</p><div><p class="Els-keywords"> </p></div>

A study on morphogenesis of roots of Panax stipuleanatus H.T.Tsai et K.M.Feng in vitro and preliminary determination of oleanolic acid in roots

Panax stipuleanatus H.T.Tsai et K.M.Feng which belongs to the genus Panax (Araliaceae family) is an valuable medicinal herbs in Vietnam and China. In the rhizome of Panax stipuleanatus H.T.Tsai et K.M.Feng contains many olean-type triterpenoid saponins, which can improve mental stamina and reduces risks of cancers in humans. Up to now, there is no research on the morphological changes in adventitious root formation from the rhizome of this species. In this study, the callus morphogenesis from the rhizome and the adventitious root morphogenesis from callus were analyzed. The rhizome segments 1-1.5 cm in diameter and 1 cm thick were cultured on MS medium supplemented 30 g/l sucrose, 6 g/l agar and 0.5 mg/l 2.4-D in dark. Callus formed on the surface of the rhizome after four weeks. The first cell divisions occurred in the first two weeks, in secondary cortex parenchyma cells and vascular cambium of the rhizome. 26-week-old callus with slow cell proliferation within the cluster and the long cells outside clusters were transferred to the induced medium supplemented with 0.5 mg/l 2.4-D and 0.1 mg/l TDZ within 6 weeks. The calli were more tight and formed many clusters. The adventitious roots formed 10 weeks after the transfer to MS medium supplemented with 0.5 mg/l NAA. Callus formed spherical structures called embryo-liked but only developed the root pole. Results of the thin layer chromatography using chloroform–methanol (9:1, v/v) showed the presence of oleanolic acid in extracts of adventitious roots fromed from callus-derived rhizomes of Panax stipuleanatus H.T.Tsai et K.M.Feng.

The localization of NADPH oxidase and reactive oxygen species in in vitro-cultured Mesembryanthemum crystallinum L. hypocotyls discloses their differing roles in rhizogenesis.

This work demonstrated how reactive oxygen species (ROS) are involved in the regulation of rhizogenesis from hypocotyls of Mesembryanthemum crystallinum L. cultured on a medium containing 1-naphthaleneacetic acid (NAA). The increase of NADPH oxidase activity was correlated with an increase of hydrogen peroxide (H2O2) content and induction of mitotic activity in vascular cylinder cells, leading to root formation from cultured hypocotyls. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, inhibited H2O2 production and blocked rhizogenesis. Ultrastructural studies revealed differences in H2O2 localization between the vascular cylinder cells and cortex parenchyma cells of cultured explants. We suggest that NADPH oxidase is responsible for H2O2 level regulation in vascular cylinder cells, while peroxidase (POD) participates in H2O2 level regulation in cortex cells. Blue formazan (NBT) precipitates indicating superoxide radical (O2 •−) accumulation were localized within the vascular cylinder cells during the early stages of rhizogenesis and at the tip of root primordia, as well as in the distal and middle parts of newly formed organs. 3,3′-diaminobenzidine (DAB) staining of H2O2 was more intense in vascular bundle cells and in cortex cells. In newly formed roots, H2O2 was localized in vascular tissue. Adding DPI to the medium led to a decrease in the intensity of NBT and DAB staining in cultured explants. Accumulation of O2 •− was then limited to epidermis cells, while H2O2 was accumulated only in vascular tissue. These results indicate that O2 •− is engaged in processes of rhizogenesis induction involving division of competent cells, while H2O2 is engaged in developmental processes mainly involving cell growth.

The morphogenesis of lupine root nodules during infection by Rhizobium lupini

The development of root nodules in <em>Lupinus luteus</em> infected by <em>Rhizobium lupini</em> was studied using cytological methods. The results obtained from examination of material sampled 6, 9, 13, 15, 20, 29 and 60 days after infection are given. The successive stages of development are described and the cytological characteristics of the tissue are presented. The mitotic divisions of the root cortex parenchyma cells, which initiated the formation of the nodule primordium, were accompanied by structural changes in the root hairs and divisions in the root pericycle. The development of the nodule was associated with the activity of the lateral meristems, which encompass both the infected cells and cells not containing bacteroids Characteristics of bacteria found in the symplast and apoplast of the bacteroid tissue are given.

Histological examination of horse chestnut infection by Pseudomonas syringae pv. aesculi and non-destructive heat treatment to stop disease progression.

Since its emergence in Northwest Europe as a pathogen that infects trunks and branches of Aesculus spp. (the horse chestnuts) approximately one decade ago, Pseudomonas syringae pv. aesculi has rapidly established itself as major threat to these trees. Infected trees exhibit extensive necrosis of phloem and cambium, which can ultimately lead to dieback. The events after host entry leading to extensive necrosis are not well documented. In this work, the histopathology of this interaction is investigated and heat-treatment is explored as method to eradicate bacteria associated with established infections. The early wound-repair responses of A. hippocastanum, both in absence and presence of P. s. pv. aesculi, included cell wall lignification by a distinct layer of phloem and cortex parenchyma cells. The same cells also deposited suberin lamellae later on, suggesting this layer functions in compartmentalizing healthy from disrupted tissues. However, monitoring bacterial ingress, its construction appeared inadequate to constrain pathogen spread. Microscopic evaluation of bacterial dispersal in situ using immunolabelling and GFP-tagging of P. s. pv. aesculi, revealed two discriminative types of bacterial colonization. The forefront of lesions was found to contain densely packed bacteria, while necrotic areas housed bacterial aggregates with scattered individuals embedded in an extracellular matrix of bacterial origin containing alginate. The endophytic localization and ability of P. s. pv aesculi to create a protective matrix render it poorly accessible for control agents. To circumvent this, a method based on selective bacterial lethality at 39°C was conceived and successfully tested on A. hippocastanum saplings, providing proof of concept for controlling this disease by heat-treatment. This may be applicable for curing other tree cankers, caused by related phytopathogens.

The Synthesis and Storage Sites of Phenolic Compounds in the Root and Rhizome of <i>Echinacea purpurea</i>

Cichoric acid is the main phenolic compound in the root and rhizome of the medicinal part, Echinacea purpurea that is known for possessing immune enhancing characteristics. In this study, we analysis the the synthesis and storage sites of phenolic compound in E. purpurea. We used fluorescent microscopy, transmission electron microscopy, cytochemical and immunocytochemical localization to observe the distribution of phenolic compounds. Our results show that the phenolic compounds were mostly distributed in the cortex parenchyma cells, vascular parenchyma cells and pith parenchyma cells in the root and rhizome, and mainly present in the vacuoles, large intercellular spaces and their surrounding cell walls. No phenolic compounds were observed in the cytoplasm and the organelles. We concluded that the phenolic compounds were synthetized in the cortex parenchyma cells, vascular parenchyma cells and pith parenchyma cells in the root and rhizome, and stored in the vacuoles of parenchyma cells. The above results provided significantly cytological information for further approaching the metabolic regulation and transfer pathways of phenolic compounds in biochemistry and molecular biology.

Cadmium tolerance in Thlaspi caerulescens: II. Localization of cadmium in Thlaspi caerulescens

Tissue and cellular compartmentation of Cd in roots and leaves of the hyperaccumulator Thlaspi caerulescens was investigated, using energy-dispersive X-ray microanalysis. In roots, Cd was determined in cortex parenchyma cells, endodermis, parenchyma cells of the central cylinder and xylem vessels. In leaves, it was found in cells lying on the way of water migration from the vascular cylinder to epidermal cells, which is in line with passive Cd transport by the transpiration stream. The mechanisms of Cd-detoxification in roots seem to be localized both in apoplast (e.g. binding to cell wall compounds) and inside cells since Cd was accumulated in these two compartments. On the other hand, in leaves Cd was found only in electron-dense deposits inside vacuoles, which suggests that vacuoles are the main compartment of its storage and detoxification in these organs.

Cadmium tolerance in Thlaspi caerulescensII. Localization of cadmium in Thlaspi caerulescens

Tissue and cellular compartmentation of Cd in roots and leaves of the hyperaccumulator Thlaspi caerulescens was investigated, using energy-dispersive X-ray microanalysis. In roots, Cd was determined in cortex parenchyma cells, endodermis, parenchyma cells of the central cylinder and xylem vessels. In leaves, it was found in cells lying on the way of water migration from the vascular cylinder to epidermal cells, which is in line with passive Cd transport by the transpiration stream. The mechanisms of Cd-detoxification in roots seem to be localized both in apoplast (e.g. binding to cell wall compounds) and inside cells since Cd was accumulated in these two compartments. On the other hand, in leaves Cd was found only in electron-dense deposits inside vacuoles, which suggests that vacuoles are the main compartment of its storage and detoxification in these organs.

Effect of Chilling on DNA Endoreplication in Root Cortex Cells and Root Hairs of Soybean Seedlings

Relative nuclear DNA contents in cortex parenchyma cells in root segments of 3- and 7-d-old soybean seedlings grown at 25 °C and in plants grown for 3 d at 25 °C, and then for 4 d at 10 °C, were determined with cytophotometry. Measurements revealed that in each variant the cortex cell nuclei with DNA content between 2C and 8C were in all the examined segments and nuclei with 8C – 16C DNA appeared in higher parts of roots. However, in chilled plant cells the number of 8C – 16C DNA nuclei was very low. Therefore, chilling inhibited endoreplication in comparison with plants grown at 25 °C for 7 d, and even reduced endopolyploidy level as compared to the initial seedlings, i.e. 3-d-old plants. DNA contents in root hairs grown at 25 °C (control) and in root hairs emerged at 10 °C were also determined. In controls 4C – 8C DNA nuclei predominated while in chilled plants an additional population of 2C – 4C DNA appeared. Thus a reduction of DNA synthesis was brought about by low temperature. The occurrence of an intermediate DNA contents besides those with full endoreplication cycles suggests the possibility of differential DNA replication. This suggestion seems to be supported by the lack of 3H-thymidine incorporation into root hair nuclei at the examined developmental stage both in control and chilled root hairs. The same number, but larger, chromocentric lumps in polyploid cortex cell nuclei of higher root zones, in comparison to meristematic nuclei, suggests that endoreduplication process occurred.

Immunohistological localization of chitinase and β-1,3-glucanase in rhizomania-diseased and benzothiadiazole treated sugar beet roots

Accumulation of plant basic β-1,3-glucanase (Glu2) and basic class IV chitinase (Ch4) was examined in rhizomania-diseased sugar beet roots and compared to plants treated with a synthetic inducer of systemic acquired resistance, benzothiadiazole (BTH). Spatial distribution of the enzymes was studied by means of immunohistology in root tissues. It was established that Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania, induced accumulation of Glu2 and Ch4 in cell walls and extracellular spaces. The deposition of the enzymes was found predominantly in endodermis, cortical cells adjacent to endodermis (Glu2 and Ch4), and xylem vessels (Glu2 only). Resting spores and plasmodia of the BNYVV vector, Polymyxa betae, were formed mainly in rhizodermis and cortex parenchyma cells; the direct co-location of P. betae infectious structures with Glu2 and Ch4 was not confirmed. BNYVV was detected unevenly in cortex parenchyma and rarely in the xylem vessels. The results indicate, that the accumulation of the defence proteins Glu2 and Ch4 is most likely connected with BNYVV multiplication or induced in a systemic mode. Similarly to the pathogens, BTH induced the deposition of both Ch4 and Glu2 systemically in cortex and endodermis cells. The extracellular localization of these hydrolases suggests the potential of BTH for protection the sugar beet against soil-borne diseases.

Fibres from semi-retted hemp bundles by steam explosion treatment

Hemp (Cannabis sativa), is an annual plant used in the pulp and paper industry. It consists of two main morphological regions, the fibre cells which are bound by the middle lamellae and arranged in bundles, themselves separated by the cortex parenchyma cells with pectic and hemicellulosic rich cell walls, and the woody core with lignified cells. Any industrial utilisation of hemp requires the separation of the fibres from the rest of the plant, which is traditionally achieved by undertaking a dew retting in the field followed by several mechanical treatments. Our objective was to substitute the slow and difficult to control retting process by a fast and well controlled process, i.e. steam explosion treatment (STEX) of semi-retted decorticated hemp bundles. During the STEX treatment the pectins and hemicelluloses are hydrolysed and rendered water- or alkali-soluble, the fibres being more easily degummed. We optimised the treatment parameters (temperature/pressure, time and pH of impregnation) and found that impregnation in alkali and steaming for 90 s at 200°C (1.5 MPa) were among the best conditions for the degumming and individualisation of the elementary fibres. After washing of the steamed material a carding mechanical treatment is necessary to separate the single fibres. The steam exploded samples were observed by scanning electron microscopy (SEM), and the morphological aspects of the steam exploded hemp fibres are discussed.

Calmodulin binding to glutamate decarboxylase is required for regulation of glutamate and GABA metabolism and normal development in plants.

Glutamate decarboxylase (GAD) catalyzes the decarboxylation of glutamate to CO2 and gamma-aminobutyrate (GABA). GAD is ubiquitous in prokaryotes and eukaryotes, but only plant GAD has been shown to bind calmodulin (CaM). Here, we assess the role of the GAD CaM-binding domain in vivo. Transgenic tobacco plants expressing a mutant petunia GAD lacking the CaM-binding domain (GADdeltaC plants) exhibit severe morphological abnormalities, such as short stems, in which cortex parenchyma cells fail to elongate, associated with extremely high GABA and low glutamate levels. The morphology of transgenic plants expressing the full-length GAD (GAD plants) is indistinguishable from that of wild-type (WT) plants. In WT and GAD plant extracts, GAD activity is inhibited by EGTA and by the CaM antagonist trifluoperazine, and is associated with a CaM-containing protein complex of approximately 500 kDa. In contrast, GADdeltaC plants lack normal GAD complexes, and GAD activity in their extracts is not affected by EGTA and trifluoperazine. We conclude that CaM binding to GAD is essential for the regulation of GABA and glutamate metabolism, and that regulation of GAD activity is necessary for normal plant development. This study is the first to demonstrate an in vivo function for CaM binding to a target protein in plants.

In situ localisation of beet necrotic yellow vein virus (BNYVV) in rootlets of susceptible and resistant beet plants.

Mechanisms of resistance to beet necrotic yellow vein virus (BNYVV) were studied by comparing the multiplication and distribution of BNYVV in root tissue of some beet accessions. Seedlings were infected either by soil containing resting spores of Polymyxa betae with BNYVV, or by a viruliferous zoospore suspension. With both inoculation methods high virus concentrations were obtained in rootlets of the susceptible cultivar 'Regina'. Using infested soil, low virus concentrations were found in the partially resistant cultivar 'Rima' and in the resistant accessions Holly and WB42. When a zoospore suspension was used, similar virus concentrations occurred in 'Rima' and Holly as in 'Regina', while a low virus concentration was found in WB42. By in situ localisation studies, using immunogold-silver labelling, virus was detected in 'Regina' after infection by soil or a zoospore suspension, but it could only be detected in the resistant accessions after infection by a zoospore suspension. In rootlets of 'Regina', 'Rima' and Holly, virus was found in the epidermis, cortex parenchyma, endodermis, and interstitial parenchyma, but in general not inside the vascular tissue. In WB42 the virus, occurring in small aggregates, seemed to be restricted to the epidermis and some cortex parenchyma cells. Comparing both the multiplication and distribution of BNYVV in rootlets of the accessions studied, it is concluded that the virus resistance mechanism in 'Rima' and Holly is different from that in WB42.

Regulation of the Osmotin Gene Promoter.

By introducing a chimeric gene fusion of the osmotin promoter and [beta]-glucuronidase into tobacco by Agrobacterium-mediated transformation, we have demonstrated a very specific pattern of temporal and spatial regulation of the osmotin promoter during normal plant development and after adaptation to NaCl. We have found that the osmotin promoter has a very high natural level of activity in mature pollen grains during anther dehiscence and in pericarp tissue at the final, desiccating stages of fruit development. GUS activity was rapidly lost after pollen germination. The osmotin promoter thus appears to be unique among active pollen promoters described to date in that it is active only in dehydrated pollen. The osmotin promoter was also active in corolla tissue at the onset of senescence. Adaptation of plants to NaCl highly stimulated osmotin promoter activity in epidermal and cortex parenchyma cells in the root elongation zone; in epidermis and xylem parenchyma cells in stem internodes; and in epidermis, mesophyll, and xylem parenchyma cells in developed leaves. The spatial and temporal expression pattern of the osmotin gene appears consistent with both osmotic and pathogen defense functions of the gene.

Morphologisch-anatomische Untersuchungen zur Ablegerbildung und sproßbürtigen Bewurzelung der Fichte (Picea abies (L.) Karst.)

Summary It was the aim of this study, to extend the knowledge on the formation of ground-layers with Norway spruce ( Picea abies (L.) K arst .), with special consideration of root formation on shoots. For this purpose natural layers and the formation of experimentally induced, newly formed roots on stems and twigs were investigated morphologically and anatomically. “Adventitious” roots on stems and twigs were mostly situated above terminal bud scars (whorls or whorl remnants). Like dormant buds the roots have continuous and broad trace connections through cortex and xylem up to the pith of the shoot. They are also very often located in close vicinity of dormant buds or within branch bark ridges (chinese beards) and find their origin in a group of meristematic cells at the basis of dormant buds in the cortex. Because of the preventitious origin of these meristems, the term “adventitious” sensu stricto [after T h . H artig ’s (1851) and R. H artig ’s (1891) definition; see also F ink (1980)] does not apply to these growths. But in single cases true adventitious roots without trace connections to the pith were found on uninjured segments of branches, which originate from shoot cambium or cortex parenchyma cells. On wounded parts the development of adventitious roots from callus tissue were noted. With the further enlargement and development of the newly formed shoot-borne root system, branch diameter and conductivity cross-section of layers were reduced in the branch segment between clonal mother tree and the site of root initiation and development, whereas the distal portions (from the well-rooted site to the top) of the layered branches increased in diameter and conductivity cross-section. Before the initiation of roots, anatomical alterations in stems and bark were determined after covering with earth. Early-wood cells of covered cuttings showed greater inner cell circumference and lower tangential cell wall thickness than untreated plants. Covered shoot bark was similar in appearance to root bark and showed lightbrown discolouring.

Localization of polyphenol oxidase activity in the lamellae and membrane-bound inclusions of etiolated soybean hypocotyl chloroplasts

Localization for polyphenol oxidase was carried out on 6-day-old etiolated soybean (Glycine max (L.) Merr.) tissue. Light and electron microscope observations of tissues exposed to the substrate L-dihydroxyphenylalanine after chemical fixation revealed that polyphenol oxidase activity was present in the lamellae and membrane-bound inclusions of chloroplasts. Inhibitors of polyphenol oxidase, diethyldithiocarbamate and phenylhydrazine, prevented formation of the reaction product. Only plastids in epidermal and associated cortex collenchyma cell layers contained inclusions and enzyme activity. Most guard cells and all cortex parenchyma cells were devoid of both. Homogenates of epidermal strips were shown to contain 95–99% of the total polyphenol oxidase activity present in hypocotyls.