Sclerenchyma Cells Research Articles

Standardization of phaseolus vulgaris valves by macro- and microscopic characteristics

During the last years on the Ukrainian pharmaceutical market a tendency to increase the range of the national herbal remedies is observed. Native flora herbs, having a sufficient resource base, deserve special attention and are characterized by a number of economic benefits for manufacturers. The implementation of herbal remedies in medical practice is accompanied by the necessity to improve the quality control of herbal material and to develop normative documents. Macro- and microscopy analysis becomes important at standardization of herbal material especially cut and powdered.Aim. The aim of our work was to carry out macro- and microscopy research of Phaseolus vulgaris and to determine its diagnostic morphologic and anatomic features.Methods. The conventional research methods in pharmacognosy have been used; photomicrography has been taken by using microscope MC-10 and Samsung PL 50 camera.Results. As a result of research, the microscopic diagnostic characteristics for Phaseolus vulgaris valves have been proposed, e.g.: the valves are elongated, straight, navicular or grooved, twisted to some extent; the external surface is smooth or slightly undulating, mat, pale yellow or yellow; the internal surface is shiny, white or yellowish-white. Sometimes carpophore (stalk) may occur. The microscopic diagnostic features have been determined and offered, e.g.: cells of outer epidermis are pentagonal and hexagonal, with plicated cuticle; stomata are surrounded by 3–4 subsidiary narrow cells, additionally surrounded by 5–6 narrow cells; cover trichomes and glandular trichomes are elongated, pointed and unbranched; xylem vessels and tracheids; non-bundled structure stalk fragments with pericyclic sclerenchyma and secretory cells in the phloem.Conclusion. Research on determination of the macro- and microscopic characteristics of Phaseolus vulgaris valves has been carried out. The diagnostic morphological and anatomic elements in herbal material have been determined for its identification. The data obtained have been used for development of the State Pharmacopoeia of Ukraine draft Monograph «Phaseolus vulgaris valves»

Semi-Rolled Leaf2 modulates rice leaf rolling by regulating abaxial side cell differentiation.

Moderate leaf rolling maintains the erectness of leaves and minimizes the shadowing between leaves which is helpful to establish ideal plant architecture. Here, we describe asrl2(semi-rolled leaf2) rice mutant, which has incurved leaves due to the presence of defective sclerenchymatous cells on the abaxial side of the leaf and displays narrow leaves and reduced plant height. Map-based cloning revealed that SRL2 encodes a novel plant-specific protein of unknown biochemical function.SRL2 was mainly expressed in the vascular bundles of leaf blades, leaf sheaths, and roots, especially in their sclerenchymatous cells. The transcriptional activities of several leaf development-related YABBY genes were significantly altered in the srl2 mutant. Double mutant analysis suggested that SRL2 and SHALLOT-LIKE1(SLL1)/ROLLED LEAF9(RL9) function in distinct pathways that regulate abaxial-side leaf development. Hence, SRL2 plays an important role in regulating leaf development, particularly during sclerenchymatous cell differentiation.

Ultrasound processing to enhance drying of cashew apple bagasse puree: Influence on antioxidant properties and in vitro bioaccessibility of bioactive compounds

The present study has evaluated the effects of power ultrasound pre-treatment on air-drying and bioactive compounds of cashew apple bagasse. The sonication induced the disruption of cashew bagasse parenchyma, which resulted in lower resistance to water diffusion, less hysteresis, and increased rehydration rate. The processing did not affect the lignocellulose fibers or the sclerenchyma cells. For sonicated samples, water activity reached values below 0.4, after 2h of drying, which is appropriate to prevent bacterial and fungi growth. The sorption isotherms of cashew apple bagasse presented sigmoid-shape for all samples and followed the type II according to BET classification. Sonicated cashew apple bagasse showed higher antioxidant activity, higher total phenolic compounds (TPC) and higher vitamin C content when compared to the non-sonicated sample. The increase in TPC and vitamin C contributed to the product antioxidant activity. A slight reduction on Vitamin C bioaccessibility was observed, but the TPC bioaccessibility has increased. Sonication reduced the quality loss of conventional drying treatments improving the quality of the dried product.

Barley NARROW LEAFED DWARF1 encoding a WUSCHEL-RELATED HOMEOBOX 3 (WOX3) regulates the marginal development of lateral organs.

Barley (Hordeum vulgare L.) is the fourth most-produced cereal in the world and is mainly utilized as animal feed and malts. Recently barley attracts considerable attentions as healthy food rich in dietary fiber. However, limited knowledge is available about developmental aspects of barley leaves. In the present study, we investigated barley narrow leafed dwarf1 (nld1) mutants, which exhibit thin leaves accompanied by short stature. Detailed histological analysis revealed that leaf marginal tissues, such as sawtooth hairs and sclerenchymatous cells, were lacked in nld1, suggesting that narrowed leaf of nld1 was attributable to the defective development of the marginal regions in the leaves. The defective marginal developments were also appeared in internodes and glumes in spikelets. Map-based cloning revealed that NLD1 encodes a WUSCHEL-RELATED HOMEOBOX 3 (WOX3), an ortholog of the maize NARROW SHEATH genes. In situ hybridization showed that NLD1 transcripts were localized in the marginal edges of leaf primordia from the initiating stage. From these results, we concluded that NLD1 plays pivotal role in the increase of organ width and in the development of marginal tissues in lateral organs in barley.

Systematic Importance of Leaf Anatomical Characters in Some Species of <i>Microcos</i> Linn. Section <i>Eumicrocos</i> Burret. in Nigeria

The leaf anatomy of six Microcos L. species belonging to section Eumicrocos in Nigeria was investigated by transverse sectioning of the lamina and examined by light microscope to determine their taxonomic significance in species delimitation and classification. The common anatomical characteristics in all the species are as follows: the uniseriate epidermis; the hypostomatic and bifacial leaves; presence of 2 layers of palisade tissues; presence of bundle sheath extension to both epidermises; presence of glandular and non-glandular trichomes; presence of secretory ducts on abaxial surface; presence of druse crystal in the mesophyll and midrib and; sclerenchyma cells associated with the phloem. Anatomical characters which are significant for species delimitation include: the presence/absence of sclerenchyma cells associated with the xylem in the midrib; presence/absence of starch grains in the mesophyll and midrib; the presence/absence of secretory ducts on the adaxial surface of the midrib; the presence/absence of medullary plates in midrib; the number of secretory ducts in the midrib and the midrib adaxial outline. The section can be separated into two distinct groups based on the number of spongy tissue layers in the mesophyll, number of sclerenchyma cells associated with the phloem and presence/absence of sclerenchyma cells in xylem both groupings correlated with those obtained from foliar epidermal and pollen characters. The importance of these characters is discussed in relation to the taxonomy of the taxon.

Fine mapping of a palea defective 1 (pd1), a locus associated with palea and stamen development in rice.

KEY MESSAGE : pd1, a genetic factor in a 69 kb region between RM11239 and RM11245 on rice chromosome 1, controls stamen number and palea development. Spikelets are important organs that store photosynthetic products in rice. Spikelet development directly affects grain yield and rice quality. Here, we report a palea defective (pd1) mutant identified from selfing progenies of indica cv. 93-11 after (60)Co γ ray treatment. pd1 mutant flowers only had four stamens (wild-type has six), but pollen fertility was not affected. Compared with 93-11 palea, pd1 mutant palea showed smaller and flatter leaf, which caused the lemma to bend excessively inward. pd1 mutants had only 46% seed setting rate and 21.6 g 1000-grain weight, which led to two-thirds loss of grain yield. Scanning electron microscope analysis revealed that pd1 mutants had reduced epidermal cell size and reduced numbers of fibrous sclerenchyma cells in both palea and lemma. To analyze the genetic factors involved, we crossed pd1 mutants with three japonica cultivars and generated F1 and F2 populations. The F1 phenotype and F2 segregation ratio indicated that a recessive gene controlled the mutant traits. Using the F2 population, we found that pd1 mapped between the simple sequence repeat markers RM11236 and RM11280 on rice chromosome 1. From a segregating population of 2836 plants, 77 recombinants were screened by RM11236 and RM11280. High-resolution linkage analysis narrowed the pd1 locus to a 69 kb region between RM11239 and RM11245 that contained 10 open reading frames (ORFs). Sequence alignment and quantitative real-time PCR expression analysis of these ORFs between 93-11 and pd1 mutant plants found no unequivocal evidence to identify the pd1 gene.

Functional Characterization of NAC and MYB Transcription Factors Involved in Regulation of Biomass Production in Switchgrass (Panicum virgatum).

Switchgrass is a promising biofuel feedstock due to its high biomass production and low agronomic input requirements. Because the bulk of switchgrass biomass used for biofuel production is lignocellulosic secondary walls, studies on secondary wall biosynthesis and its transcriptional regulation are imperative for designing strategies for genetic improvement of biomass production in switchgrass. Here, we report the identification and functional characterization of a group of switchgrass transcription factors, including several NACs (PvSWNs) and a MYB (PvMYB46A), for their involvement in regulating secondary wall biosynthesis. PvSWNs and PvMYB46A were found to be highly expressed in stems and their expression was closely associated with sclerenchyma cells. Overexpression of PvSWNs and PvMYB46A in Arabidopsis was shown to result in activation of the biosynthetic genes for cellulose, xylan and lignin and ectopic deposition of secondary walls in normally parenchymatous cells. Transactivation and complementation studies demonstrated that PvSWNs were able to activate the SNBE-driven GUS reporter gene and effectively rescue the secondary wall defects in the Arabidopsis snd1 nst1 double mutant, indicating that they are functional orthologs of Arabidopsis SWNs. Furthermore, we showed that PvMYB46A could activate the SMRE-driven GUS reporter gene and complement the Arabidopsis myb46 myb83 double mutant, suggesting that it is a functional ortholog of Arabidopsis MYB46/MYB83. Together, these results indicate that PvSWNs and PvMYB46A are transcriptional switches involved in regulating secondary wall biosynthesis, which provides molecular tools for genetic manipulation of biomass production in switchgrass.

Characterization and fine mapping of the rice gene OsARVL4 regulating leaf morphology and leaf vein development

Leaf morphology and chlorophyll content are closely related to the photosynthetic efficiency, which would potentially contribute to crop yield. In this study, we isolated an EMS-mutagenized rice mutant displaying abaxial rolling and vein-albino leaves, and thus designated it as Osarvl4. Compared to the wild type ‘Nipponbare’, Osarvl4 mutant had abnormal development of clear cells, parenchyma cells, sclerenchymatous cells, mesophyll cells, bulliform cells and vascular bundles. As a result of the defective leaf development, the chlorophyll content and photosynthetic efficiency were significantly affected in the mutant. Genetic analysis using map-based cloning indicated that the mutation was controlled by a single recessive karyogene localized within a 44 kb region on the long arm of chromosome 4. Sequence analysis and alignment indicated that the three candidate genes in this region showed no difference at the DNA level. However, quantitative real-time PCR analysis showed that the expression of the LOC_Os04g33580 gene in the mutant was significantly lower than that of wild type, while expression of the other two candidate genes (LOC_Os04g33560 and LOC_Os04g33570) exhibited no significant difference. Therefore, we speculate that LOC_Os04g33580 might be the target gene which regulates leaf vein development and leaf morphogenesis in rice and this locus might be subject to epigenetic regulation, such as DNA methylation, Thus, our finding suggests that the OsARVL4 gene is involved in the regulation of chlorophyll content and photosynthetic efficiency in plants, and provides a genetic basis for the future study of genes related to leaf development in rice.

Comparative study of Passiflora taxa leaves: I. A morpho-anatomic profile

Determining the authenticity and quality of plant raw materials used in the formulation of herbal medicines, teas and cosmetics is essential to ensure their safety and efficacy for clinical use. Some Passiflora species are officially recognized in the pharmaceutical compendia of various countries and have therapeutic uses, particularly as sedatives and anxiolytics. However, the large number of Passiflora species, coupled with the fact that most species are popularly known as passion fruit, increases the misidentification problem. The purpose of this study is to make a pharmacognostic comparison between various Passiflora species to establish a morpho-anatomical profile that could contribute to the quality control of herbal drug products that contain passion fruit. This was conducted by collecting samples of leaves from twelve Passiflora taxa (ten species and two forms of P. edulis): P. actinia, P. alata, P. amethystina, P. capsularis, P. cincinnata, P. edulis f. flavicarpa, P. edulis f. edulis, P. incarnata, P. morifolia, P. urnifolia, P. coccinea and P. setacea, from different locations and their morpho-anatomical features were analyzed using optical microscopy and scanning electron microscopy. Microscopic analysis allowed to indicate a set of characters that can help to differentiate species. These include midrib and petiole shape, midrib and petiole vascular pattern, medium vein shape, presence of trichomes, presence of blade epidermal papillae and sclerenchymatic cells adjoining the vascular bundles. These characters could be used to assist in the determination of herbal drug quality and authenticity derived from a species of Passiflora.

Brassinosteroid Signaling Regulates Leaf Erectness in Oryza sativa via the Control of a Specific U-Type Cyclin and Cell Proliferation

Leaf erectness is key in determining plant architecture and yield, particularly in cereal crops. Brassinosteroids (BRs) play a unique role in controlling this trait in monocots, but the underlying cellular and molecular mechanisms remain big mysteries. Here we report that the abaxial sclerenchyma cell number of rice lamina joints (LJs) is closely related to leaf erectness, and BR signaling tightly regulates their proliferation. We identified a rice U-type cyclin CYC U4;1 enriched in rice LJs, with its expression accompanying LJ development. Genetic and biochemical studies demonstrated that CYC U4;1 plays a positive role in promoting leaf erectness by controlling the abaxial sclerenchyma cell proliferation. Furthermore, BR signaling inhibits the abaxial sclerenchyma cell division by coordinately regulating CYC U4;1 expression through BES1 and CYC U4;1 protein activity through GSK3 kinases. These results support a key role of the cyclin CYC U4;1 in mediating BR-regulated cell division to control leaf erectness.

Activation of miR165b represses AtHB15 expression and induces pith secondary wall development in Arabidopsis.

Secondary cell-wall thickening takes place in sclerenchyma cells, but not in surrounding parenchyma cells. The molecular mechanism of switching on and off secondary wall synthesis in various cell types is still elusive. Here, we report the identification of a dominant mutant stp-2d showing secondary wall thickening in pith cells (STP). Immunohistochemistry assays confirmed accumulation of secondary cell walls in the pith cells of the stp-2d mutant. Activation of microRNA 165b (miR165b) expression is responsible for the STP phenotype, as demonstrated by transgenic over-expression experiments. The expression of three classIII HD-ZIP transcription factor genes, including AtHB15, was repressed in the stp-2d mutant. Transgenic over-expression of a mutant form of AtHB15 that is resistant to miR165-mediated cleavage reversed the stp-2d mutant phenotype to wild-type, indicating that AtHB15 represses secondary wall development in pith. Characterization of two athb15 mutant alleles further confirmed that functional AtHB15 is necessary for retaining primary walls in parenchyma pith cells. Expression analyses of cell-wall synthetic genes and wall-related transcription factors indicated that a transcriptional pathway is involved in AtHB15 function. These results provide insight into the molecular mechanism of secondary cell-wall development.

Cypselar anatomy of five species of the tribe Calenduleae, family Asteraceae

Detailed anatomical features of cypselas of five species (Calendula arvensis L., Calendula maderensis DC., Calendula stellata Cav., Calendula suffruticosa Vahl ssp. suffruticosa and Osteospermum vaillantii (Decne.) Norl.) of the tribe Calenduleae have been studied to observe the variation pattern among them. Among the five cypselas, in case of C. stellata, mesocarpic region is made up of only parenchyma cells, containing pits. In remaining four cypselas, mesocarpic region is made up of both parenchyma and sclerenchyma cells. In the cypsela of O. vaillantii, vallecular cavity is present in mesocarpic region. This cavity is absent in remaining four cypselas. In the cypsela of C. arvensis and C. suffruticosa, secretory duct exists in mesocarpic region, which is absent in remaining three cypselas. In the cypsela of C. arvensis and C. maderensis, six vascular traces are present in mesocarpic region, whereas in O. vaillantii, eight vascular traces; in C. stellata, five vascular traces; in C. suffruticosa, four vascular traces are present in mesocarpic region. Based on the above mentioned anatomical features, an artificial key to the species has been constructed.Journal of Bangladesh Academy of Sciences, Vol. 39, No. 1, 65-71, 2015

WRKY13 acts in stem development in Arabidopsis thaliana

Stems are important for plants to grow erectly. In stems, sclerenchyma cells must develop secondary cell walls to provide plants with physical support. The secondary cell walls are mainly composed of lignin, xylan and cellulose. Deficiency of overall stem development could cause weakened stems. Here we prove that WRKY13 acts in stem development. The wrky13 mutants take on a weaker stem phenotype. The number of sclerenchyma cells, stem diameter and the number of vascular bundles were reduced in wrky13 mutants. Lignin-synthesis-related genes were repressed in wrky13 mutants. Chromatin immunoprecipitation assays proved that WRKY13 could directly bind to the promoter of NST2. Taken together, we proposed that WRKY13 affected the overall development of stem. Identification of the role of WRKY13 may help to resolve agricultural problems caused by weaker stems.

Norway spruce (Picea abies) laccases: characterization of a laccase in a lignin-forming tissue culture.

Secondarily thickened cell walls of water-conducting vessels and tracheids and support-giving sclerenchyma cells contain lignin that makes the cell walls water impermeable and strong. To what extent laccases and peroxidases contribute to lignin biosynthesis in muro is under active evaluation. We performed an in silico study of Norway spruce (Picea abies (L.) Karst.) laccases utilizing available genomic data. As many as 292 laccase encoding sequences (genes, gene fragments, and pseudogenes) were detected in the spruce genome. Out of the 112 genes annotated as laccases, 79 are expressed at some level. We isolated five full-length laccase cDNAs from developing xylem and an extracellular lignin-forming cell culture of spruce. In addition, we purified and biochemically characterized one culture medium laccase from the lignin-forming cell culture. This laccase has an acidic pH optimum (pH 3.8-4.2) for coniferyl alcohol oxidation. It has a high affinity to coniferyl alcohol with an apparent Km value of 3.5 μM; however, the laccase has a lower catalytic efficiency (V(max)/K(m)) for coniferyl alcohol oxidation compared with some purified culture medium peroxidases. The properties are discussed in the context of the information already known about laccases/coniferyl alcohol oxidases of coniferous plants.

Estudo farmacobotânico de partes aéreas vegetativas de aroeira-vermelha (Schinus terebinthifolius Raddi, Anacardiaceae)

Schinus terebinthifolius Raddi (Anacardiaceae), conhecida como aroeira-vermelha é uma espécie nativa do Brasil, perenifólia e pioneira, sendo muito utilizada para combater diversas doenças, pois apresenta, entre outras, propriedades anti-inflamatórias e cicatrizantes. O objetivo desta pesquisa foi realizar um estudo morfoanatômico do caule e da folha de S. terebinthifolius, descrevendo a organização dos tecidos e suas possíveis variações. As análises macro e microscópicas foram realizadas com material selecionado de partes vegetativas de um espécime localizado na cidade de Campina Grande - PB. A aroeira-vermelha é um vegetal arbóreo e dióico, que apresenta caule cilíndrico e simpodial, com casca rugosa e estriada. A folha é perene, alterna, coriácea e composta. As análises microscópicas evidenciaram epiderme caulinar e foliar uniestratificadas, exceto na face adaxial da folha, que é bisseriada. No caule e no pecíolo são visualizados muitos tricomas tectores unicelulares, curtos, cônicos e agudos no ápice. Encontram-se canais secretores arredondados e bem desenvolvidos na região do floema em todos os órgãos estudados, bem como cutícula revestindo as células epidérmicas e grande quantidade de drusas de oxalato de cálcio. Os feixes vasculares são circundados por células esclerenquimáticas e apresentam o floema seguido por xilema helicoidal bem desenvolvido. No caule, pecíolo e nervura central da folha, o xilema é interno e o floema, externo. A aroeira-vermelha apresenta alguns aspectos estruturais característicos de plantas xerófilas, como camada múltipla da epiderme da face adaxial foliar, que protegem o mesofilo de excessiva dessecação; presença de cutícula espessa e grande quantidade de pêlos e de estômatos; além de sistema vascular bem desenvolvido, com abundância de esclerênquima, dando sustentação ao feixe.

A new Late Devonian genus with seed plant affinities.

BackgroundMany ovules of Late Devonian (Famennian) seed plants have been well studied. However, because few taxa occur with anatomically preserved stems and/or petioles, the vascular system of these earliest spermatophytes is little understood and available data come mostly from Euramerica. There remains great controversy over the anatomical differentiation of Late Devonian and Carboniferous seed plant groups of Buteoxylonales, Calamopityales and Lyginopteridales. Protostele evolution of these early spermatophytes needs more research.ResultsA new taxon Yiduxylon trilobum gen. et sp. nov. with seed plant affinities has been discovered in the Upper Devonian (Famennian) Tizikou Formation of Hubei Province, China. It is represented by stems, helically arranged and bifurcate fronds with two orders of pinnae and planate pinnules. Both secondary pinnae and pinnules are borne alternately. Stems contain a small protostele with three primary xylem ribs possessing a single peripheral protoxylem strand. Thick secondary xylem displays multiseriate bordered pitting on the tangential and radial walls of the tracheids, and has biseriate to multiseriate and high rays. A narrow cortex consists of inner cortex without sclerotic nests and sparganum-type outer cortex with peripheral bands of vertically aligned sclerenchyma cells. Two leaf traces successively arise tangentially from each primary xylem rib and they divide once to produce four circular-oval traces in the stem cortex. Four vascular bundles occur in two C-shaped groups at each petiole base with ground tissue and peripheral bands of sclerenchyma cells.ConclusionsYiduxylon justifies the assignment to a new genus mainly because of the protostele with protoxylem strands only near the periphery of primary xylem ribs, leaf trace origination and petiolar vascular supply structure. It shares many definitive characters with Calamopityales and Lyginopteridales, further underscoring the anatomical similarities among early seed plants. The primary vascular system, pycnoxylic-manoxylic secondary xylem with bordered pits on both tangential and radial walls of a tracheid and leaf trace divergence of Yiduxylon suggest transitional features between the early spermatophytes and ancestral aneurophyte progymnosperms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0292-6) contains supplementary material, which is available to authorized users.

Structure and biomechanics of culms of Phragmites australis used for reeds of Japanese wind instrument "hichiriki".

Hichiriki is a traditional Japanese double-reed wind instrument used in Japanese ancient imperial court music, gagaku, which has been performed since the 7th century. The best reeds for hichiriki have been made of culms or stems of Phragmites australis (P. australis) that are harvested from only a limited reed bed at Udono near Kyoto. The aim of this study is to elucidate why the stems from Udono are the best materials for hichiriki reeds. Plant anatomy was examined for choice stems of P. australis grown in different reed beds in Japan as well as morphology, and the local indentation hardness and Young's modulus of tissues on the cross-sections of some representatives of hichiriki reeds were measured. It is concluded that the good stems for hichiriki reeds have an outer diameter of about 11 mm, a wall thickness of about 1 mm and comparatively homogeneous structure where harder materials, such as epidermis, hypodermis, sclerenchymatous cells, and vascular bundle sheaths with hard walls, are orderly deployed with softer materials such as parenchyma cells and vascular bundles. This structure has smaller differences of hardness and Young's modulus between the hard and soft materials in the reed, providing the best music performance.

Study on morphology and anatomy of Akebia trifoliate seeds

Akebia trifoliate has been reported to have many pharmacological activities and the roots, petioles and seeds are used to different symptoms. However, the structure and anatomy of its seeds was almost not reported until now. In the present study, we investigated the morphological characters of the fruit and seed, and the anatomical characters of the testa, micropyle, embryo and endosperm, which could provide evidences for the study on classification, identification and application of A. trifoliate. Our results showed that the testa of A. trifoliate consisted of an epidermic cell layer, the sclerenchyma cells layer, the parenchyma cells layer and an innermost pigment layer. At the micropylar region, the outermost epidermal cells were specialized the white caruncle-like structure and the testa included a lot of lignified tissues. Endosperm comprises two layer cells. Outermost yellowish-brown layer cells contains lots of fat droplets, and innermost white layer cells contains lots of aleurone grains and crystalloids.

Observations on anatomical aspects of the fruit, leaf and stem tissues of four Citrullus spp.

Morphological characteristics of the fruit, stem and leaf tissues of four species of Citrullus (L.) Schrad. were examined using standard histological methods. Plant materials included the cultivated watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) and three of its related species (Citrullus colocynthis (L.) Schrad., Citrullus ecirrhosus Cogn. and Citrullus rehmii de Winter). Variation among the species was observed in the thickness of the subepidermal layer(s) of the fruit, this layer being thicker in fruits of C. ecirrhosus (~ 200 uM) than in fruits of C. lanatus (~100 uM), C. colocynthis (~100 uM) or C. rehmii.(~100 µM). Variation was also observed in the extent and organization of the subtending sclerenchymatous cells which were up to 10 layers thick in fruits of C. colocynthis, 1 or 2 cell layers thick in the fruits of C. lanatus., and an intermediate number of layers (3 to 6) in fruits of C. ecirrhosus and C. rehmii. A greater degree of lignifications was observed in the stem tissue of C. colocynthis and C. ecirrhosus, in comparison with that of C. lanatus and C. rehmii. Leaf thickness (~250 µM) was similar among three of the four species examined, but was reduced in C. rehmii (~150 µM). Further study is required to assess the possible contribution of these, and other, morphological attributes to drought tolerance in members the genus Citrullus. Key words: Watermelon, Citrullus lantatus, Citrullus colocynthis, Citrullus rehmii, Citrullus ecirrhosus, histology, anatomy, structure, drought tolerance, caudex, pollen viability.

Glycoside Hydrolase Activities in Cell Walls of Sclerenchyma Cells in the Inflorescence Stems of Arabidopsis thaliana Visualized in Situ.

Techniques for in situ localization of gene products provide indispensable information for understanding biological function. In the case of enzymes, biological function is directly related to activity, and therefore, knowledge of activity patterns is central to understanding the molecular controls of plant development. We have previously developed a novel type of fluorogenic substrate for revealing glycoside hydrolase activity in planta, based on resorufin β-glycosides Here, we explore a wider range of such substrates to visualize glycoside hydrolase activities in Arabidopsis inflorescence stems in real time, especially highlighting distinct distribution patterns of these activities in the secondary cell walls of sclerenchyma cells. The results demonstrate that β-1,4-glucosidase, β-1,4-glucanase and β-1,4-galactosidase activities accompany secondary wall deposition. In contrast, xyloglucanase activity follows a different pattern, with the highest signal observed in mature cells, concentrated in the middle lamella. These data further the understanding of the process of cell wall deposition and function in sclerenchymatic tissues of plants.