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Degradação in vitro de tecidos da lâmina foliar e do colmo de gramíneas forrageiras tropicais, em função do estádio de desenvolvimento

Paciullo, Domingos Sávio Campos; Gomide, José Alberto; Silva, Eldo Antônio Monteiro da; Queiroz, Domingos Sávio; Gomide, Carlos Augusto Miranda
Fonte: Sociedade Brasileira de Zootecnia Publicador: Sociedade Brasileira de Zootecnia
Tipo: Artigo de Revista Científica Formato: 900-907
POR
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O experimento foi realizado com o objetivo de avaliar o efeito da idade sobre o potencial de degradação dos diferentes tecidos da lâmina foliar e do colmo de capim-braquiária (Brachiaria decumbens), capim-gordura (Melinis minutiflora) e capim-tifton 85 (Cynodon sp). Foram amostradas a 7ª (capim-braquiária e capim-gordura) e a 11ª (capim-tifton 85) lâminas foliares, no dia da exposição da lígula e 20 dias após. Por meio de observações ao microscópio foram estimadas a extensão da digestão in vitro dos tecidos da lâmina e do colmo e a redução na espessura da parede de células do esclerênquima do colmo. Lâminas foliares e segmentos de colmos jovens apresentaram maiores áreas digeridas. Permaneceram intactos os tecidos com células de parede espessada e lignificada, a bainha parenquimática dos feixes, o esclerênquima, o xilema e a epiderme do colmo. Tecidos com células de parede delgada, normalmente não-lignificada, o mesofilo, o floema e o parênquima, desapareceram completamente. O avanço na idade reduziu a digestão do mesofilo, em lâminas de capim-braquiária e capim-gordura, e do parênquima em colmos, principalmente de capim-gordura. A epiderme na lâmina foliar foi parcialmente digerida, independentemente da idade e da espécie. Embora aparentemente intactas...

Características anatômicas da lâmina foliar e do colmo de gramíneas forrageiras tropicais, em função do nível de inserção no perfilho, da idade e da estação de crescimento

Paciullo, Domingos Sávio Campos; Gomide, José Alberto; Silva, Eldo Antônio Monteiro da; Queiroz, Domingos Sávio; Gomide, Carlos Augusto Miranda
Fonte: Sociedade Brasileira de Zootecnia Publicador: Sociedade Brasileira de Zootecnia
Tipo: Artigo de Revista Científica Formato: 890-899
POR
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Foram avaliados os efeitos da idade, do nível de inserção da folha no perfilho e da estação de crescimento (verão ou outono), sobre a proporção de tecidos e a espessura da parede celular em lâminas foliares e segmentos de colmo de capim-braquiária (Brachiaria decumbens), capim-gordura (Melinis minutiflora) e capim-tifton 85 (Cynodon sp). Lâminas foliares das posições inferior e superior do perfilho foram colhidas no dia da exposição da lígula e 20 dias após. Foram determinadas as proporções relativas de epiderme, xilema, floema, bainha parenquimática dos feixes, esclerênquima, parênquima no colmo e mesofilo na lâmina foliar. Foram medidas as espessuras das paredes dos vasos de metaxilema e do esclerênquima da lâmina e do colmo. A proporção de tecidos em lâminas foliares não foi alterada pela idade nem pela estação de crescimento, sendo a espessura da parede de células do esclerênquima da lâmina a única característica modificada pela idade. Lâminas do nível de inserção superior apresentaram mais elevadas proporções de esclerênquima, bainha parenquimática dos feixes e xilema e células do esclerênquima e do metaxilema com paredes mais espessas, enquanto as lâminas do nível de inserção inferior se destacaram por apresentar mais elevada proporção de mesofilo e paredes celulares mais delgadas. Enquanto a proporção de parênquima decresceu...

Collenchyma in Panicum maximum (Poaceae): localisation and possible role

Paiva, EAS; Machado, SR
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica Formato: 69-73
ENG
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This work relates the occurrence and distribution of collenchyma in Panicum maximum Jacq. P. maximum leaves were collected at different phases of development and sampled from both the base of the sheath and from the sheath-leaf blade transition area. For the stems, the study was made by using hand-cut sections of the internodal base. In the leaves, analyses of serial sections showed, at the base and sheath-leaf blade transition area, a sudden change of tissue at vascular bundle. The vascular bundles are surrounded by sclerenchyma, both in the sheath and the leaf blade, as well as by fibrous threads that occur on the adaxial side of the central bundles. However, at the base of the sheath and at the sheath-leaf blade transition area, sclerenchyma was substituted for collenchyma. In the stem, the substitution of sclerenchyma associated with vascular bundles for collenchyma occurs at the base of the internode, in the pulvinus region. The analyses from transmission electron microscopy showed the presence of lamellated cell wall and active protoplast in collenchyma cells.

Anatomia de escapos, folhas e brácteas de Syngonanthus sect. Eulepis (Bong. ex Koern.) Ruhland (Eriocaulaceae)

Scatena, Vera Lucia; Vich, Daniele Vital; Parra, Lara Regina
Fonte: Sociedade Botânica do Brasil Publicador: Sociedade Botânica do Brasil
Tipo: Artigo de Revista Científica Formato: 825-837
POR
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Estudou-se a anatomia de escapos, folhas e brácteas de 24 espécimes de Syngonanthus sect. Eulepis, que ocorrem nos campos rupestres do Brasil. Os escapos apresentam número variado de costelas, epiderme unisseriada, com células de paredes totalmente espessadas; córtex com esclerênquima e parênquima clorofiliano alternados; endoderme contínua ou descontínua; periciclo estrelado; feixes vasculares colaterais; medula com células de paredes finas ou espessadas. As folhas e as brácteas apresentam epiderme com células de paredes total ou parcialmente espessadas, estômatos na face abaxial, margem com parênquima clorofiliano ou esclerênquima; mesofilo com hipoderme constituída de esclerênquima ou parênquima aqüífero, feixes vasculares colaterais envolvidos externamente pela endoderme e internamente pelo periciclo. Escapos, folhas e brácteas de Syngonanthus sect. Eulepis apresentam células com paredes espessadas e grande quantidade de esclerênquima, provavelmente como resposta adaptativa dessas plantas ao vento e à radiação excessiva comum nos campos rupestres. Epiderme com células de paredes espessadas, estômatos com câmara subestomática não especializada, presença de hipoderme, esclerênquima, e parênquima clorofiliano compacto...

Anatomia foliar de espécies do gênero Scleria (Cyperaceae)

Hoss, Kátia Arenhart
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Dissertação de Mestrado Formato: 72 p.| il., tabs.
POR
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Biologia Vegetal, Florianópolis, 2013.; O gênero Scleria, pertence à família Cyperaceae e suas espécies caracterizam-se por serem ervas perenes e cespitosas, que ocupam preferencialmente ambientes úmidos, podendo ser encontrados também em outros locais, como campos e matas. A delimitação do gênero Scleria tem sido muito controversa, pois assim como a maioria das espécies de Cyperaceae, a morfologia externa de seus órgãos vegetativos é muito similar, as flores são muito reduzidas e a inflorescência é difícil de interpretar. Em função disso, foi analisada a anatomia foliar de Scleria distans, S. gaertneri, S. latifolia, S. leptostachya, S. panicoides, S. plusiophylla, S. secans, S. sellowiana, S. uleana e S. variegata, coletadas no estado de Santa Catarina, com o objetivo de verificar a ocorrência de características anatômicas que possam distinguir as espécies. E ainda foi analisada a origem dos feixes invertidos que ocorrem nas folhas da espécie de S. plusiophylla. O material coletado foi processado de acordo com técnicas usuais em estudos de anatomia e ontogenia. Os caracteres anatômicos comuns às espécies são: formato de W invertido da lâmina foliar em secção transversal...

Leaf tissues degradation of signalgrass hay pretreated with urea and submitted to in vitro digestion

Gobbi,Kátia Fernanda; Garcia,Rasmo; Ventrella,Marília Contin; Garcez Neto,Américo Fróes; Pereira,Odilon Gomes
Fonte: Sociedade Brasileira de Zootecnia Publicador: Sociedade Brasileira de Zootecnia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2008 EN
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An experiment using signalgrass hay treated with increasing urea levels (0, 20, 40, and 80 g/kg of dry matter), and submitted to in vitro digestion times (0, 6, 12, 24 or 72 hours) was conducted to evaluate the effects of ammoniation rates and digestion times on leaf blade tissue degradation. A completely randomized design with a 4 × 5 factorial treatment arrangement, with three replicates was used. Data were submitted to multivariate analysis. Urea-treated hay presented smaller proportion of remaining tissues measured in leaf blades cross-sections after in vitro digestion. Tissues more affected by urea treatment degradation were parenchyma bundle sheath and sclerenchyma. The hay treated with 80 g urea/kg DM and in vitro digested for 24 or 72 hours showed smallest proportion of tissues with thick and lignified cell walls such as parenchyma bundle sheath and sclerenchyma. The treatment with urea also reduced the time necessary to tissue degradation. The urea-treated hay in vitro digested for 12 hours, showed the same tissue proportion found in untreated hay submitted to 24 or 72 hours of in vitro digestion. The epidermis and lignified vascular tissue showed the smallest degradation following in vitro digestion. Results indicated that treatment of signalgrass hay with urea contributed to cell wall structure disruption...

Leaf anatomy changes related to physiological adaptations to flooding in Amazonian tree species

Herrera,Ana; Escala,Marcia; Rengifo,Elizabeth
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
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In trees of the seasonally flooded forest of the Mapire River in Venezuela, early flooding induces a reversible diminution in leaf conductance and photosynthetic rate. With the aim of finding an anatomical explanation for the observed responses of leaf gas exchange, the characteristics of emerged leaves developed under drainage or after three months of flooding were examined in the tree species Acosmium nitens, Campsiandra laurifolia, Duroia fusifera, Eschweilera tenuifolia, Pouteria orinocoensis and Symmeria paniculata and in leaves developed only under flooding in Inga spuria and Tachigali davidsei. Anatomy was remarkably similar among species and families and consisted of a bi-layered palisade parenchyma, a 5-6-cell-thick spongy parenchyma and large whole-leaf thickness. Anatomy also resembled that of xerophytes or evergreen species by possessing thick cuticles, large epidermal cells, thickened anticlinal epidermal cell walls and an abundance of sclerenchyma. Leaves of flooded v. un-flooded trees were not qualitatively different. Specific leaf area resembled values of deciduous species in tropical dry forests. No quantitative differences were found between leaves developed in un-flooded and flooded trees, with the exception of a reduction in whole-leaf thickness of E. tenuifolia...

Down-Regulation of Caffeic Acid O-Methyltransferase in Maize Revisited Using a Transgenic Approach1

Piquemal, Joel; Chamayou, Simon; Nadaud, Isabelle; Beckert, Michel; Barrière, Yves; Mila, Isabelle; Lapierre, Catherine; Rigau, Joan; Puigdomenech, Pere; Jauneau, Alain; Digonnet, Catherine; Boudet, Alain-Michel; Goffner, Deborah; Pichon, Magalie
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /12/2002 EN
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Transgenic maize (Zea mays) plants were generated with a construct harboring a maize caffeic acid O-methyltransferase (COMT) cDNA in the antisense (AS) orientation under the control of the maize Adh1 (alcohol dehydrogenase) promoter. Adh1-driven β-glucuronidase expression was localized in vascular tissues and lignifying sclerenchyma, indicating its suitability in transgenic experiments aimed at modifying lignin content and composition. One line of AS plants, COMT-AS, displayed a significant reduction in COMT activity (15%–30% residual activity) and barely detectable amounts of COMT protein as determined by western-blot analysis. In this line, transgenes were shown to be stably integrated in the genome and transmitted to the progeny. Biochemical analysis of COMT-AS showed: (a) a strong decrease in Klason lignin content at the flowering stage, (b) a decrease in syringyl units, (c) a lower p-coumaric acid content, and (d) the occurrence of unusual 5-OH guaiacyl units. These results are reminiscent of some characteristics already observed for the maize bm3 (brown-midrib3) mutant, as well as for COMT down-regulated dicots. However, as compared with bm3, COMT down-regulation in the COMT-AS line is less severe in that it is restricted to sclerenchyma cells. To our knowledge...

Mixed fungal populations and lignocellulosic tissue degradation in the bovine rumen.

Akin, D E; Rigsby, L L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1987 EN
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Anaerobic fungi in ruminal fluid from cows eating Bermuda grass hay plus a grain and minerals supplement were evaluated for diversity in sporangial morphotypes and colony growth patterns and for the degradation of various lignocelluloses. In selective cultures containing streptomycin and penicillin, an active population of ruminal fungi colonized leaf blades and degraded fiber at rates and extents almost equal to that of the total ruminal population. Three major sporangial morphotypes were consistently observed on leaf blades: oval, globose, and fusiform. Fungal colonies representing three distinct growth types consistently developed in anaerobic roll tubes inoculated with strained ruminal fluid. Sporangial morphotypes could not be matched to colony types due to multiple sporangial forms within a colony. Under identical growth conditions, one type exhibited a monocentric growth pattern, while two types exhibited polycentric growth patterns previously unreported in ruminal fungi. Mixed ruminal fungi in selective cultures or in digesta taken directly from the rumen produced a massive clearing of the sclerenchyma. Quantitation of tissue areas in cross sections by light microscopic techniques showed that fungal incubations resulted in significant (P = 0.05) increases in sclerenchyma degradation compared to whole ruminal fluid incubations. The mestome cell wall was at times penetrated and partially degraded by fungi; the colonization was less frequent and to a lesser degree than with the sclerenchyma. Conversely...

Adhesion of Bacteroides succinogenes in pure culture and in the presence of Ruminococcus flavefaciens to cell walls in leaves of perennial ryegrass (Lolium perenne).

Latham, M J; Brooker, B E; Pettipher, G L; Harris, P J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1978 EN
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Bacteroides succinogenes and Ruminococcus flavefaciens are two of the most important cellulolytic bacteria in the rumen. Adhesion of B. succinogenes in pure culture, and in mixed culture with R. flavefaciens, to the various types of cell walls in sections of perennial ryegrass (Lolium perenne L. cultivar S24) leaves was examined by transmission and scanning electron microscopy. B. succinogenes adhered to the cut edges of most plant cell walls except those of the meta- and protoxylem. It also adhered, though in much smaller numbers, to the uncut surfaces of mesophyll, epidermal, and phloem cell walls. In mixed culture, both species adhered in significant numbers to the cut edges of most types of plant cell wall, but R. flavefaciens predominated on the epidermis, phloem, and sclerenchyma cell walls. B. succinogenes predominated on the cut edges and on the uncut surfaces of the mesophyll cell walls, and its ability to adhere to uncut surfaces of other cell walls was not affected by the presence of the ruminococcus. Both organisms rapidly digested the epidermal, mesophyll, and phloem cell walls. Zones of digestion were observed around bacteria of both species when attached to the lignified cell walls of the sclerenchyma, but not when attached to the lignified xylem vessels.

Evaluation by electron microscopy and anaerobic culture of types of rumen bacteria associated with digestion of forage cell walls.

Akin, D E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1980 EN
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Different morphological types of rumen bacteria which degraded cell walls of forage grasses with various in vitro digestibilities were evaluated with electron microscopy. The majority of these bacteria (i.e., about 70% or more) consisted of two distinct types: (i) encapsulated cocci and (ii) irregularly shaped bacteria, resembling major fiber digesters found in the rumen. Each type was capable of degrading structurally intact cell walls. Differences (P less than or equal to 0.02) in the percent ratio of encapsulated cocci to irregularly shaped bacteria were observed between Bermuda grass and fescue; the ratio of encapsulated cocci to irregularly shaped bacteria between Bermuda grass and orchard grass was similar and variations were high. The proportion of irregularly shaped bacteria usually increased with increased time of digestion. Differences (P greater than 0.1) were not found in the percentage ratio of encapsulated cocci to irregularly shaped bacteria attached to specific tissue types in either Bermuda grass or fescue. However, encapsulated cocci tended to be more prevalent on sclerenchyma than other tissues in Bermuda grass, but less prevalent on sclerenchyma than other tissues in fescue. Transmission electron microscopy of tissue digestion of rapidly degraded orchard grass blades revealed that mesophyll...

Attack on Lignified Grass Cell Walls by a Facultatively Anaerobic Bacterium

Akin, Danny E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1980 EN
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A filamentous, facultatively anaerobic microorganism that attacked lignified tissue in forage grasses was isolated from rumen fluid with a Bermuda grass-containing anaerobic medium in roll tubes. The microbe, designated 7-1, demonstrated various colony and cellular morphologies under different growth conditions. Scanning electron microscopy revealed that 7-1 attacked lignified cell walls in aerobic and anaerobic culture. 7-1 predominately degraded tissues reacting positively for lignin with the chlorine-sulfite stain (i.e., sclerenchyma in leaf blades and parenchyma in stems) rather than the more resistant acid phloroglucinol-positive tissues (i.e., lignified vascular tissue and sclerenchyma ring in stems), although the latter tissues were occasionally attacked. Turbidimetric tests showed that 7-1 in anaerobic culture grew optimally at 39°C at a pH of 7.4 to 8.0. Tests for growth on plant cell wall carbohydrates showed that 7-1 grew on xylan and pectin slowly in aerobic cultures but not with pectin and only slightly with xylan in anaerobic culture. 7-1 was noncellulolytic as shown by filter paper tests. The microbe used the phenolic acids sinapic, ferulic, and p-coumaric acids as substrates for growth; the more highly methoxylated acids were used more effectively.

Culm Strength of Barley 1: Correlation Among Maximum Bending Stress, Cell Wall Dimensions, and Cellulose Content

Kokubo, Akira; Kuraishi, Susumu; Sakurai, Naoki
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1989 EN
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17.21%
Grass culms are known to differ in breaking strength, but there is little physicochemical data to explain the response. The fourth internode of four brittle and two nonbrittle barley (Hordeum vulgare L.) strains were used for physical and chemical studies of culm strength. Inner and outer culm diameters of brittle strains (3.6 ± 0.2 and 5.0 ± 0.1 millimeters) were not significantly different from those of nonbrittle strains (3.9 ± 0.2 and 5.2 ± 0.2 millimeters). Maximum bending stress, at which the culm was broken, was 192 ± 34 g/mm2 for brittle and 490 ± 38 g/mm2 for nonbrittle strains. Wall thickness and cell dimensions of epidermal, sclerenchyma, and parenchyma cells were measured in culm cross sections. The area of cell wall per unit cell area for each tissue was significantly correlated with the maximum bending stress (r = 0.93 for epidermis, 0.90 for sclerenchyma, and 0.84 for parenchyma). Cell walls of brittle culms had 6 to 64% as much cellulose content as those of nonbrittle culms. Maximum bending stress correlated significantly with cellulose content of the cell walls (r = 0.93), but not with the contents of noncellulosic compounds. The lower cellulose content of the brittle culm was significantly correlated with brittleness.

Fractionation of cell-wall preparations from grass leaves by centrifuging in non-aqueous density gradients.

Gordon, A H; Bacon, J S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/03/1981 EN
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1. Dried preparations of cell walls from perennial-ryegrass (Lolium perenne) and Italian-ryegrass (L. multiflorum) leaves were suspended in mixtures of carbon tetrachloride with light-petroleum (b.p. 45--50 degrees C) or alcohols and layered on density gradients formed from the same solvents. 2. On centrifugation, the cell walls become distributed throughout a suitably chosen gradient. Fractions corresponding to various regions of the gradient were separated, examined under the microscope and analysed. 3. Cell-wall preparations made from leaf material ground in liquid N2, or in a triple roll mill, showed considerable heterogeneity in particle size, and their behaviour in the density gradient was variable, although there was a general indication that walls derived from vascular bundles were less dense than those from sclerenchyma. 4 Treatment in a vibratory ball mill decreased the size of the particles and produced a more uniform material, but made it impossible to distinguish the origins of the particles. This material behaved more reproducibly in the density gradient. 5. Some fractionations were also made by successive centrifugation in media of increasing relative density. 6. Analyses of the fractions obtained by each method indicated that the less dense had a greater proportion of xylose in the polysaccharide components...

Rice BRITTLE CULM 5 (BRITTLE NODE) is Involved in Secondary Cell Wall Formation in the Sclerenchyma Tissue of Nodes

Aohara, Tsutomu; Kotake, Toshihisa; Kaneko, Yasuko; Takatsuji, Hiroshi; Tsumuraya, Yoichi; Kawasaki, Shinji
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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Several brittle culm (bc) mutants known in grasses are considered excellent materials to study the process of secondary cell wall formation. The brittle phenotype of the rice bc5 (brittle node) mutant appears exclusively in the developed nodes, which is distinct from other bc mutants (bc1, 2, 3, 4, 6 and 7) that show the brittle phenotype in culms and leaves. To address the defects of the rice bc5 mutant in node-specific cell wall formation, we analyzed tissue morphology and cell wall composition. The bc5 mutation was found to affect the cell wall deposition of node sclerenchyma tissues at 1 week after heading, the stage at which the cell wall sugar content is reduced, in the bc5 nodes, compared with wild-type nodes. Moreover, decreased accumulation of lignin and thickness of cell walls in the sclerenchyma tissues were also observed in the bc5 nodes. The amounts of cellulose and hemicellulose were reduced to 53 and 65% of those in the wild-type plants, respectively. Sugar composition and glycosidic linkage analyses of the hemicellulose showed that the accumulation of glucuronosyl arabinoxylan in bc5 nodes was perturbed by the mutation. The bc5 locus was narrowed to an approximately 3.1 Mb region of chromosome 2, where none of the other bc genes is located. The bc5 mutation appeared to reduce the expression levels of the OsCesA genes in the nodes after heading. The results indicate that the BC5 gene regulates the development of secondary cell walls of node sclerenchyma tissues.

Silicon enhances suberization and lignification in roots of rice (Oryza sativa)

Fleck, Alexander T.; Nye, Thandar; Repenning, Cornelia; Stahl, Frank; Zahn, Marc; Schenk, Manfred K.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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The beneficial element silicon (Si) may affect radial oxygen loss (ROL) of rice roots depending on suberization of the exodermis and lignification of sclerenchyma. Thus, the effect of Si nutrition on the oxidation power of rice roots, suberization and lignification was examined. In addition, Si-induced alterations of the transcript levels of 265 genes related to suberin and lignin synthesis were studied by custom-made microarray and quantitative Real Time-PCR. Without Si supply, the oxidation zone of 12 cm long adventitious roots extended along the entire root length but with Si supply the oxidation zone was restricted to 5 cm behind the root tip. This pattern coincided with enhanced suberization of the exodermis and lignification of sclerenchyma by Si supply. Suberization of the exodermis started, with and without Si supply, at 4–5 cm and 8–9 cm distance from the root tip (drt), respectively. Si significantly increased transcript abundance of 12 genes, while two genes had a reduced transcript level. A gene coding for a leucine-rich repeat protein exhibited a 25-fold higher transcript level with Si nutrition. Physiological, histochemical, and molecular-biological data showing that Si has an active impact on rice root anatomy and gene transcription is presented here.

Hydrogen peroxide is involved in the acclimation of the Mediterranean shrub, Cistus albidus L., to summer drought

Jubany-Marí, Tana; Munné-Bosch, Sergi; López-Carbonell, Marta; Alegre, Leonor
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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This study evaluated the possible role of hydrogen peroxide (H2O2) in the acclimation of a Mediterranean shrub, Cistus albidus L., to summer drought growing under Mediterranean field conditions. For this purpose, changes in H2O2 concentrations and localization throughout a year were analysed. H2O2 changes in response to environmental conditions in parallel with changes in abscisic acid (ABA) and oxidative stress markers, together with lignin accumulation, xylem and sclerenchyma differentiation, and leaf area were also investigated. During the summer drought, leaf H2O2 concentrations increased 11-fold, reaching values of 10 μmol g−1 dry weight (DW). This increase occurred mainly in mesophyll cell walls, xylem vessels, and sclerenchyma cells in the differentiation stage. An increase in ABA levels preceded that of H2O2, but both peaked at the same time in conditions of prolonged stress. C. albidus plants tolerated high concentrations of H2O2 because of its localization in the apoplast of mesophyll cells, xylem vessels, and in differentiating sclerenchyma cells. The increase in ABA, and consequently of H2O2, in plants subjected to drought stress might induce a 3.5-fold increase in ascorbic acid (AA), which maintained and even decreased its oxidative status...

Differences in Stylet Sheath Occurrence and the Fibrous Ring (Sclerenchyma) between xCitroncirus Plants Relatively Resistant or Susceptible to Adults of the Asian Citrus Psyllid Diaphorina citri (Hemiptera: Liviidae)

Ammar, El-Desouky; Richardson, Matthew L.; Abdo, Zaid; Hall, David G.; Shatters, Robert G.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 24/10/2014 EN
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27.21%
The Asian citrus psyllid (ACP, Diaphorina citri, Hemiptera: Liviidae), is the principal vector of the phloem-limited bacteria strongly associated with huanglongbing (HLB), the world’s most serious disease of citrus. Host plant resistance may provide an environmentally safe and sustainable method of controlling ACP and/or HLB. Two xCitroncirus accessions (hybrids of Poncirus trifoliata and Citrus spp.), that are relatively resistant (UN-3881) or relatively susceptible (Troyer-1459) to ACP adults with regard to adult longevity, were compared in relation to ACP feeding behavior and some structural features of the leaf midrib. The settling (putative feeding/probing) sites of ACP adults on various parts of the leaf were not influenced primarily by plant accession. However, fewer ACP stylet sheaths were found in the midrib and fewer stylet sheath termini reached the vascular bundle (phloem and/or xylem) in UN-3881 compared to Troyer-1459 plants. Furthermore, in midribs of UN-3881 leaves the fibrous ring (sclerenchyma) around the phloem was significantly wider (thicker) compared to that in midribs of Troyer-1459 leaves. Our data indicate that feeding and/or probing by ACP adults into the vascular bundle is less frequent in the more resistant (UN-3881) than in the more susceptible (Troyer-1459) accessions. Our results also suggest that the thickness of the fibrous ring may be a barrier to stylet penetration into the vascular bundle...

Leaf tissues proportion and chemical composition of Axonopus jesuiticus x A. scoparius as a function of pig slurry application

Lajús,Cristiano Reschke; Miranda,Mário; Basso,Simone Meredith Scheffer; Carneiro,Cercí Maria; Escosteguy,Pedro Alexandre Varella
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2014 EN
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This study aimed to evaluate the chemical and anatomical attributes of leaves of giant missionary grass to application of 0, 62, 124, 186, 248 and 310m³ ha-1 of pig slurry. At 83 days after the last application of fertilizer, the leaf blades were collected, fixed in FAA 70%, sectioned, stained, photographed and digitalized. The transversal section of leaf blades were evaluated for proportion of epidermis, lignified vascular tissue + sclerenchyma, non-lignified vascular tissue and parenchyma with an image-processing system calibrated to 1mm pixel-1. Leaf samples were analyzed for crude protein, acid detergent fiber, neutral detergent fiber and hemicellulose content by near infrared reflectance spectroscopy. The pig slurry application up to 310m³ ha-1 significantly increased the percentage of crude protein, parenchyma, epidermis, non-lignified vascular tissue and hemicellulose, while decreasing the percentage of acid detergent fiber and lignified vascular tissue + sclerenchyma. The Pearson's correlation was positive between crude protein and non-lignified vascular tissue, and between acid detergent fiber and lignified vascular tissue + sclerenchyma. The percentage of hemicellulose was positively correlated with epidermis, parenchyma and non-lignified vascular tissue. A negative correlation between acid detergent fiber and epidermis...

Micro-morphology and anatomy of Turbinicarpus (Cactaceae) spines

Mosco,Alessandro
Fonte: Instituto de Biología Publicador: Instituto de Biología
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2009 EN
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Spines are a striking feature of cacti and display wide variation in size, number, shape, and texture. This study showed that Turbinicarpus species exhibit not only a high variability in the gross morphology of the spines, but also in their micro-morphology. Their surface can be smooth or ornamented with projections that can be low, conical, pinnate, or long trichomes. The epidermis can be continuous, broken up into single cell elements or transversely fissured, the fissures extending deeply into the underlying sclerenchyma. The mechanical properties of the spines are related to their anatomy, here documented for the first time. The woody rigid spines being made up of fibers with thick walls (> 3 µm), while papery or corky spines have a sclerenchyma made up of fibers with thin walls (< 2 µm). Alternatively, spine anatomy can be dimorphic with the outermost layers made up of thin-walled fibers and an inner core made up of thick-walled fibers. Turbinicarpus taxonomy mostly relies on spine features and the newly collected data can contribute to a better understanding of the interspecific relationships. The epidermal features like long trichomes or the lack of ornamentation as well as the modified anatomy of corky spines may be apomorphic characters within the genus.