Development of intraxylary phloem and internal cambium in Ipomoea hederifolia (Convolvulaceae)

V. S. PATIL (Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390002 India), K. S. RAO (BRD School of Bioscieces, S. P. University, Vallabh Vidyanagar, India), and K. S. RAJPUT (Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390002 India). Development of intraxylary phloem and internal cambium in Ipomoea hederifolia (Convolvulaceae). J. Torrey Bot. Soc. 136: 423-432. 2009-In Ipomoea hederifolia L. (Convolvulaceae), internal/intraxylary phloem originated as isolated strands from the procambially derived cells after the formation of protoxylem and protophloem. Bands of internal phloem were apparent in the sixth internode after the development of metacambium. In the relatively thick stems several small arcs/segments of internal cambium ensues from the parenchyma cells between the protoxylem and internal protophloem. Though all the segments were active, some of them (two of them located opposite to each other) were relatively more active. Bidirectional differentiation of these segments gave rise to secondary xylem centrifugally and secondary phloem centripetally, resulting inverted vascular bundles. Rest of the internal cambium segments were unidirectional and formed only secondary phloem centripetally. Like external vascular cambium, the internal cambium was non-storied. Structurally, secondary xylem and phloem was composed of axial and radial system in which rays were mostly uni- to biseriate. Secondary xylem produced by the internal cambium was more or less similar to the xylem formed by the external successive cambia. Secondary phloem produced by the internal cambium was composed of sieve tubes, companion cells, axial and ray parenchyma cells. Simple sieve plates of internal phloem were mostly arranged on transverse end walls in contrast to compound and obliquely placed sieve plates of external phloem formed by the successive cambia.

Enraizamento de estacas de Ginkgo biloba tratadas com ácido indolbutírico e ácido bórico

Objetivou-se neste trabalho estudar o efeito do ácido indolbutírico (AIB) e do ácido bórico (B) no enraizamento de estacas de Ginkgo biloba. em estacas com duas folhas, medindo 15 cm de comprimento foram provocadas duas lesões na base de aproximadamente 2 cm, expondo o câmbio e procedeu-se à imersão por 10 segundos no tratamento correspondente, AIB (0, 1000, 2000 e 3000 mg L-1) na ausência ou presença de B (0 e 150 mg L-1). em seguida foram colocadas para enraizar em bandejas de polipropileno contendo areia lavada. O delineamento foi em blocos casualizados num fatorial 4X2, com seis repetições. Foram avaliadas porcentagem de estacas enraizadas, estacas não enraizadas e mortas, diâmetro e comprimento das raízes, aos 70 dias do tratamento. Os dados foram submetidos à análise de variância sendo previamente testados para normalidade pelo Teste de Shapiro-Wilk. As médias foram comparadas pelo Teste de Tukey. Os tratamentos com 2000 mg L-1 de AIB foram superiores à ausência de AIB (80,55% vs. 55,56%, respectivamente), não diferindo dos demais tratamentos. A utilização de B não afetou a taxa de enraizamento, de estacas não enraizadas e mortas, não havendo interação entre a concentração de AIB e a utilização ou não de B. O diâmetro e o comprimento das raízes não foram afetados pela utilização de AIB e B.

Seasonal variation in wood formation of Cedrela fissilis (Meliaceae)

Cambial activity and periodicity of secondary xylem formation in Cedrela fissilis, a semi-ring-porous species, were studied. Wood samples were collected periodically from 1996 to 2000. The phenology was related to climate data of the region. The cambium has one active and one dormant period per year. The active period coincides with the wet season when trees leaf-out. The dormant period coincides with the dry season when trees lose their leaves. Growth rings are marked by parenchyma bands that begin to be formed, together with the small latewood vessels, just before the cambium becomes dormant at the beginning of the dry season. These bands are added to when the cambium reactivates in the wet season. At this time, the large earlywood vessels of the growth rings are also formed. As these bands consist of both terminal and initial parenchyma, we suggest the general term marginal bands be used to describe them. The growth layers vary in width among and within the trees.

STEM ANATOMY and DEVELOPMENT of SUCCESSIVE CAMBIA IN THE NEOTROPICAL LIANA SECURIDACA RIVINIFOLIA (POLYGALACEAE)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alterações anatômicas foliares em plantas de Brachiaria subquadripara submetidas à aplicação de herbicidas

O presente trabalho teve por objetivo avaliar a eficiência do controle dos herbicidas diquat, glyphosate e imazapyr e as alterações anatômicas do limbo foliar provocadas por eles em plantas de Brachiaria subquadripara. As plantas foram cultivadas em caixas-d'água sob condições de campo e, quando atingiram estádio de pleno desenvolvimento vegetativo, foram pulverizadas com soluções de diquat a 400 g ha-1, glyphosate a 4.320 g ha-1 em associação com o adjuvante Aterbane a 0,5% v v-1 e imazapyr a 750 g ha-1. Além disso, utilizou-se uma testemunha sem aplicação de herbicida. Foram realizadas avaliações de controle e das seguintes características anatômicas quantitativas das regiões da nervura central e da internervural do limbo foliar, além da região do colmo: porcentagem da epiderme adaxial e abaxial, porcentagem da endoderme, porcentagem do feixe vascular, porcentagem de lacunas do aerênquima, porcentagem de parênquima, espessura foliar, porcentagem da epiderme do colmo, porcentagem do câmbio vascular e diâmetro do colmo. Os herbicidas diquat e imazapyr promoveram o maior número de alterações nos caracteres anatômicos quantitativos das regiões da nervura central e internervural do limbo foliar e da região do colmo das plantas. Contudo, com exceção do diquat, os herbicidas foram eficientes no controle das plantas de B. subquadripara, porém todos eles permitiram a rebrota delas.

Ontogênese de caneluras em pedúnculo de flores de laranjeira doce infectados pelo vírus da tristeza dos citros estirpe Capão Bonito

Um estudo da ontogênese das caneluras induzidas em ramos de laranjeiras doces suscetíveis por isolados severos do vírus da tristeza dos citros (Citrus tristeza vírus - CTV) foi feito usando-se como modelo pedúnculos florais e de frutos. O menor calibre destes órgãos permite um melhor acompanhamento do processo. As observações foram feitas em laranjeira cv. Pêra infetada pelo isolado severo Capão Bonito do CTV. Cinco fases do processo de formação de caneluras puderam ser deduzidas pelas análises anatômicas. As primeiras alterações são representadas pelo aparecimento de células adensadas, hipertrofia e hiperplasia no parênquima e câmbio do floema e uma desorganização generalizada desta área. Segue-se uma atividade intensa do câmbio do floema adjacente e sua expansão em direção ao xilema. Esta invasão do xilema resulta na ruptura do anel do xilema pela massa celular do floema constituída de células recém formadas de parede celular delgada. Esta invasão do floema em direção ao xilema inicia um processo de degeneração dos vasos e parênquima do xilema. Finalmente há um colapso completo da região do xilema invadida, que é substituída pela massa do floema, resultando na canelura, notada ao se remover a casca.

Seasonal presence of acicular calcium oxalate crystals in the cambial zone of Citharexylum myrianthum (Verbenaceae)

This study focuses on the seasonal presence of acicular crystals in the cambial zone of Citharexylum myrianthum Chain. (Verbenaceae). Specimens collected in different months from 1996 to 2000 were examined for the abundance of acicular crystals in the cambium. This information was correlated with the phenology of the species and the climate of the region. Acicular calcium oxalate crystals were found in cambial fusiform and ray cell initials, as well as in their daughter cells. An abundance of crystals was observed during periods of water deficit and leaf fall (July). Fewer crystals were found in the beginning of the wet season and bud swelling (September). When trees were flowering and the soil was wet (November and December), acicular crystals were rarely observed. During this period, acicular crystals were found in differentiating phloem and xylem parenchyma cells, in fully differentiated phloem cells, but not in fully differentiated xylem cells.

Development of Intra- and Interxylary Secondary Phloem in Coccinia indica (Cucurbitaceae)

Stern anatomy and the development of intraxylary phloem were investigated in six to eight years old Coccinia indica L. (Cucurbitaceae). Secondary growth in the stems was achieved by the normal cambial activity. In the innermost part of the thicker stems, xylem parenchyma and pith cells dedifferentiated into meristematic cells at several points. In some of the wider rays, ray cells dedifferentiate and produce secondary xylem and phloem with different orientations and sometimes a complete bicollateral vascular bundle. The inner cambial segments of the bicollateral vascular bundle (of primary growth) maintained radial arrangement even in the mature stems but in most places the cambia were either inactive or showed very few cell divisions. Concomitant with the obliteration and collapse of inner phloem (of bicollateral vascular bundles), parenchyma cells encircling the phloem became meristematic forming a circular sheath of internal cambia. These internal cambia produce only intraxylary secondary phloem centripetally and do not produce any secondary xylem. In the stem, secondary xylem consisted mainly of axial parenchyma, small strands of thick-walled xylem derivatives, i.e. vessel elements and fibres embedded in parenchymatous ground mass, wide and tall rays along with exceptionally wide vessels characteristic of lianas. In thick stems, the axial parenchyma de-differentiated into meristem, which later re-differentiated into interxylary phloem. Fibre dimorphism and pseudo-vestured pits in the vessels are also reported.

Development of successive cambia and structure of wood in Gallesia integrifolia (Spreng.) Harms (Phytolaccaceae)

Stem diameter in Gallesia integrifolia (Spreng.) Harms (Phytolaccaceae) increases by forming concentric rings of xylem alternating with phloem, which show frequent anastomoses. After a period of primary growth and the formation of first (normal) ring of vascular cambium, further successive rings are initiated outside this cambium. The second ring of cambium originates from the pericycle parenchyma located between the proto-phloem, and the pericycle fibres. Each cambium produces centripetally secondary xylem and centrifugally secondary phloem. Differentiation of xylem precedes that of phloem and the first elements formed are always xylem fibres. Structurally, the vascular cylinder is composed by successive rings of secondary xylem and phloem. These rings are separated by wide bands of conjunctive parenchyma tissue. Presence of collateral vascular bundles with irregular orientation is observed in the region of anastomoses of two or more bands of conjunctive tissue. These bundles are surrounded by isodiametric, lignified and thick-walled cells. In some of the cambial rings, occurrence of polycentric rays was also noticed; these rays are tall, and characterized by the presence of meristematic regions that differentiated into thick-walled elements of secondary xylem. Origin and development of the successive cambia and the structure of xylem are discussed.

Atividade antagônica in vitro de isolados de Trichoderma spp. ao fungo Phytophthora citrophthora

Gummosis is among the main fungal diseases of the citrus. It is caused by Phytophthora sp. and usually shows up in the lap of the plant, provoking rottenness and gum exudation, and expands causing the plant death for constrictions in the cambium or phloem which interrupts the descending flow of sap. The objective of this work was to evaluate the antagonistic in vitro activity of Trichoderma spp. to the fungi Phytophthora citrophthora. Phytophthora citrophthora was exposed to five environments of antagonism (without antagonist and with four strains of Trichoderma viride, T. virens, T. harzianu and T stromaticum), The in vitro essay was accomplished through the method of paired cultures. A completely randomized desing was used with five treatments and three replications, and each plot was represented by three petri dishes. The isolates of Trichoderma demonstrated significant effect in the inhibition of the mycelial growth of the fungi Phytophthora citrophthora, and the fungi Trichoderma stromaticum presented larger antagonism to the fungi P. citrophthora while the T harzianum presented antagonism smaller.

Morfo-anatomia do eixo vegetativo aéreo de Achyrocline alata (Kunth) DC. (Asteraceae)

Achyrocline alata occurs in a dense and low vegetation in Mato Grosso do Sul State, Brazil and it has been studied under physical-chemical and yield aspects, being scarce anatomical data. The present work has as objective the study of the aerial vegetative axis. Stem is cylindrical and hairy, having five wings, which are arisen from their leaves. The blade shows the presence of uniseriate epidermis, which is covered by the cuticle of variable thickness; and non-glandular and glandular trichomes. The non-glandular trichomes are uniseriate and multicellular and have their apex cell in whip form, while the glandular trichomes are multicellular, uniseriate or biseriate. The mesophyll is dorsiventral with uni-stratified palisade parenchyma in most of the cases and lacunal parenchyma formed by three to four layers of irregular cells. Only one collateral vascular bundle occurs in the midvein. Stem in transversal section is covered by epidermis with trichomes similar to leaves; the cortex is constituted by a discontinuous area of angular collenchyma, which is followed by chlorophyll parenchyma. Vascular cylinder that is delimited by pericycle shows vascular bundles of collateral type. In the secondary structure, the periderm is originated from epidermal and subepidermal tissues. In vascular region, the fascicular cambium differs into secondary xylem and phloem, while interfascicular cambium produces sclerenchymatous tissue.

Stem anatomy and development of successive cambia in Hebanthe eriantha (Poir.) Pedersen: A neotropical climbing species of the Amaranthaceae

Hebanthe eriantha (Poir.) Pedersen, a climbing species of the Amaranthaceae increases in stem thickness by forming successive cambia. The family is dominated by herbaceous species and is constantly under discussion due to its disputed nature of the meristem. In the young stem small alternate segments of vascular cambium cease to divide and new arc of cambium initiates outside to it. The newly formed arcs connect with pre-existing alternate segments of cambium to complete the ring. On the contrary, in thick stems, instead of small segments, complete ring of cambium is replaced by new one. These new alternate segments/cambia originate from the parenchyma cells located outside to the phloem produced by previous cambium. Cambium is storied and exclusively composed of fusiform initials while ray cells remain absent at least in the early part of the secondary growth. However, large heterocellular rays are observed in 15-mm diameter stems but their frequency is much lower. In some of the rays, ray cells become meristematic and differentiate into radially arranged xylem and phloem elements. In fully grown plants, stems are composed of several successive rings of secondary xylem alternating with secondary phloem. Secondary xylem is diffuse-porous and composed of vessels, fibres, axial parenchyma while exceptionally large rays are observed only in the outermost regions of thick stems. Vessel diameter increases progressively from the centre towards the periphery of stems. Although the origin of successive cambia and composition of secondary xylem of H. eriantha remains similar to other herbaceous members of Amaranthaceae, the occurrence of relatively wider and thick-walled vessels and large rays in fully grown plants is characteristic to climbing habit. © 2013 Springer-Verlag Wien.

Estrutura, origem e desenvolvimento de laticíferos e coléteres em plantas de Tabernaemontana catharinensis A.DC. (Rauvolfioideae, Apocynaceae) em diferentes fases do desenvolvimento vegetativo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sistema vascular e atividade cambial em Alibertia concolor (Cham) k. Schum. (Rubiaceae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identicação e caracterização de dois promotores de eucalipto: com padrão de expressão ubíquo e específico de câmbio

Pós-graduação em Ciências Biológicas (Genética) - IBB