Layers Of Palisade Parenchyma Research Articles

Morfologia das plântulas, anatomia e venação dos cotilédones e eofilos de três espécies de Mimosa (Fabaceae, Mimosoideae)

A fase pós-seminal é uma das mais críticas do ciclo de vida dos vegetais, responsável pelo estabelecimento do indivíduo. Mimosa é um gênero amplo, com espécies utilizadas para recuperação de áreas degradadas; o conhecimento de fases juvenis é indispensável para a identificação no campo. Este trabalho compara a morfologia das plântulas, a anatomia e a venação dos cotilédones e eofilos de Mimosa daleoides, M. dolens var. anisitsii e M. orthacantha, adotando métodos usuais em morfologia e microscopia de luz. A germinação ocorre entre um e três dias. São plântulas fanero-epígeo-foliáceas, com expansão dos cotilédones entre dois a cinco dias após a germinação; cotilédones semelhantes, actinódromos e anfiestomáticos. A filotaxia dos cotilédones é oposta e dos eofilos é alterna. O número de pares de folíolos no primeiro eofilo varia de dois a três em M. daleoides e M. dolens var. anisitsii e de cinco a sete em M. orthacantha. O limbo foliolar apresenta anatomia semelhante entre as espécies, é anfiestomático, dorsiventral, com uma camada de parênquima paliçádico bem desenvolvida; a epiderme de M. dolens var. anisitsii apresenta idioblastos fenólicos e apêndices lignificados no bordo foliolar. O padrão de venação é broquidódromo, com algumas variações em M. orthacantha. Os resultados obtidos permitem a identificação de espécies de Mimosa em sua fase juvenil, fornecendo dados que podem apoiar estudos taxonômicos e ecológicos com o gênero.

Anatomical structure and surface micromorphology of tomatillo leaf and flower (Physalis ixocarpa Brot., Solanaceae)

Tomatillo (<em>Physalis ixocarpa</em> Brot.) is a newly introduced cultivated plant in Poland. Its anatomy was investigated in light and scanning electron microscopes. Tomatillo adult leaf had one layer of palisade parenchyma. The 1-2 cell layers of spongy parenchyma situated just below the palisade parenchyma showed large, tightly packed cells with great druses. The remaining spongy parenchyma was built of cells showing several extensions. Peculiarity of the sepals were the stomata situated on columns or hills formed of many cells. The petals had a very loose mesophyl. Their adaxial epidermis was composed of papillate cells. Such structure of the petal epidermis probably contributes to light dispersion and prevents glittering. There were several types of trichomes on the leaves, sepals and petals, some of them glandular and some simple. The large, very ramified, dendritic trichomes situated on the petals at the entry to the ovary might eventually protect it against excessive drying. The pollen grain was spherical, three-colpate. The style had a hollow channel inside. The stigma was of a wet, pa-pillate type. Sometimes thorny trichomes were found among papillae.

Plinia edulis - leaf architecture and scanning electron micrographs

Many species of Myrtaceae, including Plinia edulis (Vell.) Sobral (cambucá), have pharmacological properties and are used as hypoglycemiants and therapeutic agents against stomach problems and throat infections. Samples were collected from Tijuca Forest in Rio de Janeiro, and the morpho-anatomical data were compared with other specimens obtained from Trindade, Paraty, found in the literature. Variations in leaf anatomy were observed, and the possible causes for these effects are discussed. The plant material collected from Tijuca Forest was analyzed using scanning electron and optical microscopy. Histochemical tests were applied to identify starch, lipids, phenolic compounds and lignin. The epidermal cells exhibit straight or slightly sinuous anticlinal walls covered by a smooth cuticle with granules of wax. Simple trichomes are restricted to the midrib region, and paracytic stomata are only observed on the abaxial leaf surface. The mesophyll is dorsiventral, with conspicuous intercellular spaces in the spongy parenchyma. Intercalated columns of crystalliferous cells and subepidermal secretory cavities are observed in the single layer of palisade parenchyma. The samples obtained from Trindade, Paraty, show larger leaves, anomocytic stomata and trichomes scattered throughout the leaf surface. This plasticity might reflect leaf adaptations to environmental factors or different stages of leaf development.

STRUCTURE OF XEROPHYTIC PLANTS FROM SOUTHERN AFRICA. LEAF ANATOMY OF ANTIZOMA MIERSIANA AND DIOSPYROS RAMULOSA

An anatomical investigation of the leaves of Antizpma miersiana (Menispermaceae) and Diospyros ramulosa (Ebenaceae), both xerophytic, woody evergreen species, was conducted. Specimens were collected in the arid regions of Namaqualand in southern Africa. A number of classical xeromorphic features are present in A. miersiana, namely thick, cutinized outer epidermal cell walls, a thick epicuticular wax layer, sunken stomata, and mesophyll tissue consisting of a number of palisade parenchyma layers. Two notable features are papillose epidermal cells and large secretory cavities in the mesophyll or associated with the vascular bundles. The leaves of D. ramulosa do not exhibit many features which may be regarded as xeromorphic. An obvious feature of this species is the occurrence of phenolic deposits in the mesophyll and epidermal cells. The leaf anatomy is discussed in relation to its ecological significance.

Study on the Morphology of Genus Arabidopsis in Iran

In the present research, we have investigated morphologicaltraits of different organs of Arabidopsis species in Iran. Trichomes on the aerial parts of three species were studied under anatomical microscopy. The species exist in Iran include: Arabidopsis thaliana (Heynh), Arabidopsis pumila (steph) and Arabidopsis wallichii (Hook & thomas). The form of trichomes, basal and stemleaves, fruit length, the attitude of fruit, the existence of trichomes on the fruit, and the color ofpetal are morphological traits which separate the species. Anatomical traits of the leaf and stem of studied species were analyzed using an optical microscope. In the stem, some traits such as the shape of stem in transverse incision, the thickness of skin, the existence of supporting tissue around phloem, the number of xylem and phloem and the wavy form of stele were distinct in the three species. In the leaf, some traits such as the shape of leaf, the number of palisade parenchyma layers, the uniformity of mesophyll tissue, and the density of trichomes were different in the three species. No significant difference has been observed in the study of reproductive meristem, except in A. wallichii. The only difference was related to the size of reproductive meristem of two species and the number of flowers produced from the meristems.

English

  This study was performed to investigate the effects of water and light intensity on the growth and anatomical aspects (that is, stomatal density and chloroplasts ultrastructure) of cork oak (Quercus suber L.) seedlings from acorns collected from Tabarka (Northern Tunisia). Seedlings, four-month after germination, were planted at 3 L pots with artificial soil and were cultivated for 5 months at the greenhouse. The experiments were divided into two treatments: Water stress (well-watered: 25 to 35% of water contents, moderate drought stress: 15 to 20%, and severe drought stress: 7 to 10%) and light intensity stress (full sunlight: 100% of full sunlight, 1,200μmol m-2 s-1; moderate sunlight: 65 to 70% of full sunlight, 800 μmol m-2 s-1; low sunlight: 20 to 25% of full sunlight, 300 μmol m-2 s-1; and extremely low sunlight: 3 to 4% of full sunlight, 40 μmol m-2 s-1). Growth varied among water stress, but this variation was typically smaller than light intensity. Seedlings grown under well-watered treatment showed the increased above ground growth as compared with deep root growth of severe drought stress. In contrast, seedlings grown under severe drought stress increased in root growth than in the above ground part. Q. suber seedlings grown under the shade-exposed low light intensity indicated adaptation such as the increased leaf area and increased specific leaf area than the leaves grown in full sunlight. In different light intensity treatments, the highest specific leaf area indicated at the extremely low light. Seedlings grown under severe drought stress increased in root growth. The palisade parenchyma chloroplasts of well-watered treatment were well developed: their shape was regular, chloroplast envelope membranes and grana were distinct, and an abundance of starch grains and a scarce of plastoglobuli was also visible inside in the chloroplasts. In severe drought stress, the ultrastructural features of the abaxial leaf surface were folded and shrunken, and was observed in a higher stomatal frequency, the thicker palisade and spongy parenchyma (containing three layers of palisade parenchyma). The severe drought stress indicated a swelling and disruption of the thylakoid, large starch grains, increased plastoglobuli, and accumulation of the reactive oxygen species (ROS), hydrogen peroxide (H2O2). The main features in the chloroplasts ultrastructure caused by the extremely low sunlight revealed not only the higher grana stacks and the broader grana, but also the higher stacking degree of thylakoids. Furthermore, seedlings grown under the extremely low sunlight showed no starch or exhibited only little starch in the chloroplasts, occupied the intracellular space in all organelles, and presented numerous small vacuoles and lipid droplets in the cytoplasm of these cells as compared with the well-watered and the severe drought stress. These results suggested that Q. suber has a well-developed mechanism to drought compared with shade stress by structural adaptations such as a deeper root system, a smaller reduction in stomatal density, and a smaller leaf area.   Key words: Water stress, light intensity stress, growth, stomatal density, palisade parenchyma, starch grains, plastoglobuli, Quercus suber L.

Structural changes in Psidium guajava 'Paluma' leaves exposed to tropospheric ozone

Psidium guajava 'Paluma' has being tested as an ozone (O3) bioindicator and responds with pigmentation between the veins on the adaxial surface, due to the accumulation of phenolic compounds. These compounds act as non-enzymatic antioxidants that neutralize reactive oxygen species (ROS), formed from O3. This study aimed to evaluate the leaf structure of plants with and without visible symptoms and to establish these symptoms at the cellular level. Beside this we also aimed to detect structural changes that can minimize the effects of the O3 on the plant. The accumulation of phenolic substances, stomatal density and structural changes in P. guajava 'Paluma' leaf tissues exposed during the four seasons of the year were evaluated. The study was conducted at the Parque Estadual das Fontes do Ipiranga ( PEFI), which is a park in the city of São Paulo that has high levels of O3. Leaves with symptoms showed, on the adaxial surface, anthocyanin accumulation in the vacuoles of epidermal cells and hypodermis. When the symptoms were more intense this accumulation was observed even in the first three layers of palisade parenchyma. Comparing symptomatic and asymptomatic leaves, there was higher accumulation of phenolic compounds in the symptomatic leaves. Some parenchyma cells adjacent to substomatal chambers showed intrusive growth towards the stomatal pore, promoting its occlusion, which could reduce the entry of O3 in the leaf. The accumulation of anthocyanins and other phenolic compounds, in addition to the occlusion of the chamber, protect the plant against O3 effects. These features and the compact arrangement of the mesophyll contribute to why Psidium guajava 'Paluma' does not present cell death, a symptom usually observed in species sensitive to O3.

Morfo-anatomia foliar de Myrcia multiflora (Lam.) DC. - Myrtaceae

Folhas de Myrcia multiflora (Lam.) DC. são usadas na medicina popular como hipoglicemiantes. O objetivo deste trabalho foi caracterizar morfológica e anatomicamente as folhas desta planta, de modo que os dados obtidos possam ser utilizados como referência em exames de controle de qualidade de amostras de fármacos, com vistas a verificar a autenticidade. Folhas inteiras foram diafanizadas e coradas para o estudo da nervação. Secções transversais do pecíolo e transversais e paradérmicas da lâmina foliar foram analisadas em microscópio óptico (MO) e a superfície do limbo foi observada, também, em microscopia eletrônica de varredura (MEV). Foram aplicados testes histoquímicos em material fresco, para identificação e localização de glicídios, amido, taninos, lignina, cristais e sílica. Morfologicamente, a folha é simples, oval-elíptica, com margem inteira, base aguda, ápice acuminado e textura cartácea. A venação é do tipo camptódromo-broquidódromo. Anatomicamente, a folha é hipostomática, com mesofilo compacto e dorsiventral, com três estratos de parênquima paliçádico. A epiderme é uniestratificada, silicificada em algumas regiões e as células exibem paredes anticlinais retas. Em posição subepidérmica ocorrem numerosas cavidades secretoras de óleos essenciais. Os feixes vasculares são colaterais e acompanhados por séries cristalíferas. Os dados obtidos são comparados com os de outras espécies de Myrtaceae e conclui-se que as características morfológicas e anatômicas de M. multiflora contribuem para a diagnose.

Leaf anatomy and micromorphology of six Posoqueria Aublet species (Rubiaceae)

Abstract The present study deals with the leaf anatomy and leaf surface of Posoqueria acutifolia Mart., P. latifolia Mart., P. longiflora Aublet, P. macropus Mart., P. palustris (Rudge) Roem. and Posoqueria sp., collected in fragments of Atlantic rain forest, Rio de Janeiro, Brazil. The epicuticular wax may occur in the form of filaments, granules or crusts. The leaves are covered by a thick cuticular layer that may be smooth or striated. Paracytic stomata, and non-glandular trichomes are limited to the abaxial surface; the latter are numerous in P. palustris, and rare in P. longiflora and P. latifolia. Leaves have a dorsiventral structure, with only one layer of palisade parenchyma and varied amounts of spongy parenchyma. Idioblasts containing crystalliferous sand were observed, and were more abundant in P. latifolia. The leaf blade vascular system is formed by collateral bundles with a parenchymatous sheath, associated with fibers. The vascular system of the petiole and the leaf blade forms an arch. Some of the anatomical features observed can be used to distinguish the species studied. Anatomical leaf characters could be used in the recognition of six species of Posoqueria studied, such as anticlinal wall of epidermal cells, wax deposition, trichomes and shape of the leaf margin.

Authentication of Euclea natalensis leaf by botanical identification

Microscopical characters are well established criteria in the identification and authentication of herbal drugs. Leaves of Euclea natalensis A. DC. (Ebenaceae) are commonly used in the treatment of headache and toothache, as well as for abdominal complaints and as purgative [1]. The purpose of this study was to determine the most relevant diagnostic characters to identify leaves of E. natalensis by light microscopy (LM) and scanning electronic microscopy (SEM). Used methodology includes the microscopic analysis of the whole, fragmentised and powdered dried leaves (minimum of 30 adult leaves). Results showed that among the most useful micro characters for leaf identification are the following: a thick cuticle on both epidermises; the dorsiventral organization of the mesophyll, with one to two cell layers of palisade parenchyma on the upper epidermis and spongy parenchyma with rounded cells on the lower epidermis; the midrib vascular bundle surrounded by a sclerenchymatous tissue; the xylem with numerous small vessels, radially arranged; the presence of calcium oxalate prism crystals; numerous paracytic and diacytic stomata frequent in lower epidermis with an irregular distribution and conical unicellular non-glandular trichomes, with thick walls, sometimes curved near the base and are also fairly abundant (Image 1). A developed collenchyma is present under the lower epidermis of the midrib area and near the upper epidermis. The powdered material is characterized by the presence of fragments containing the above named structures. Obtained results can be useful on quality control protocols involving this medicinal plant.

Anatomy and morphology of photinia (Photinia × fraseri Dress) in vitro plants inoculated with rhizobacteria

Photinia × fraseri Dress (photinia) is a woody plant with high ornamental value. The anatomy and morphology of micropropagated photinia inoculated with the plant growth-promoting rhizobacteria Azospirillum brasilense and Azotobacter chroococcum, in combination with pulses of 49.2 μM indole-3-butyric acid during rhizogenesis, were characterized using light and electron microscopy. Leaves of inoculated in vitro plants showed better development than those subjected to auxin control only. All inoculated treatments, independent of the bacterial strain used, had leaves with two layers of palisade parenchyma, a thick cuticle and linear unicellular trichomes. There was no proliferation of undifferentiated tissue in any treatment and the plants showed shoot–root vascular connections. Ex vitro leaves and in vitro plants inoculated with Azospirillum brasilense Cd and Azotobacter chroococcum 42 had large stomata with elliptic aperture radially surrounded by small stomata on the abaxial foliar surface. In addition, plants of these treatments had a large root hair zone over the root surface. Bacteria were only observed on surfaces of root hairs. The results suggest that the structural changes induced by bacterial inoculation of photinia in vitro plants could lead to better adaptation to ex vitro conditions after transplanting.

Influence of ventilation and sucrose on growth and leaf anatomy of micropropagated potato plantlets

Potato single nodes were cultured in vessels containing MS medium supplemented with 10, 20 and 30 g/l of sucrose. Vessels were closed with a clear polypropylene lid with or without 10 mm microporous polypropylene membrane. Sucrose concentration significantly increased plantlet height, shoot fresh weight and chlorophyll a content. Plantlets grown in ventilated vessels were significantly shorter, had lower shoot fresh weight and higher shoot dry weight than those in non-ventilated vessels. The highest leaf chlorophyll a content (21.83 mg/g fresh weight) was found in plantlets grown in ventilated vessels using MS medium with 20 g/l of sucrose, whereas those grown on medium with 10 g/l of sucrose had the highest chlorophyll b content (24.00 mg/g fresh weight). Total chlorophyll content was significantly higher when plantlets were grown in ventilated vessels containing medium with 10 or 30 g/l sucrose than in non-ventilated vessels. There was no significant difference in total chlorophyll content among plantlets grown in ventilated vessels with different concentrations of sucrose. Stomatal density was significantly lower when plants were grown under ventilated conditions. Leaf replica examination showed that stomata under non-ventilated condition were spherical with wide openings whereas, those in ventilated vessels were elliptical with narrow openings. Plantlets grown in non-ventilated vessels had thinner leaves and failed to build up a distinct defined upper epidermis, palisade parenchyma layer and spongy cells. On the other hand, leaves under ventilated conditions showed comparatively well organized layers with small intercellular space. The vascular system of leaves under the ventilated conditions demonstrated very well developed xylem unlike leaves under non-ventilated conditions. Thus, ventilated vessels with the 20 g/l of sucrose under ambient CO 2 in the growth room could successfully promote photomixotrophic culture and produce healthy plantlets.

Morphological and anatomical evaluation of adult and juvenile leaves of olive plants

The olive tree (Olea europaea L.), like many other woody plants, has a long juvenile period in which the plant is not able to produce flowers. Knowledge of the moment when the plant is capable of flowering is important for breeding programs and also for determining the physiological basis for sexual reproductive behavior, but currently the only indicator of that moment is the actual flowering. In many species, the juvenile-to-adult phase shift includes changes in leaf structure known as heteroblasty, that is, varied form of successive leaves on the same plant. Some differences have been observed between juvenile and adult olive leaves, particularly in size and form, but to our knowledge, no complete systematic study has been carried out. In this research, we measured size, morphology and anatomy for juvenile and adult leaves of olive plants grown from seeds. Differences were found in most of the parameters studied, including leaf size, form, mesophyll thickness, layers of palisade parenchyma and quantity of peltate trichomes, which were generally significant but overlapping between the two leaf types. The most consistent and striking difference was the presence of an organized layer of subepidermal cells only in the abaxial mesophyll of adult leaves. This characteristic could be a simple and effective criterion of phase change in the olive tree.

Variability in Populus leaf anatomy and morphology in relation to canopy position, biomass production, and varietal taxon

Twelve poplar (Populus) genotypes, belonging to different taxa and to the sections Aigeiros and Tacamahaca, were studied during the third growing season of the second rotation of a high density coppice culture. With the objective to highlight the relationships between leaf traits, biomass production and taxon as well as the influence of canopy position, anatomical and morphological leaf characteristics (i.e. thickness of epidermis, of palisade and spongy parenchyma layers, density and length of stomata, leaf area, specific leaf area (SLA) and nitrogen concentration) were examined for mature leaves from all genotypes and at two canopy positions (upper and lower canopy). Above ground biomass production, anatomical traits, stomatal and morphological leaf characteristics varied significantly among genotypes and between canopy positions. The spongy parenchyma layer was thicker than the palisade parenchyma layer for all genotypes and irrespective of canopy position, except for genotypes belonging to the P. deltoides × P. nigra taxon (section Aigeiros). Leaves at the upper canopy position had higher stomatal density and thicker anatomical layers than leaves at the lower canopy position. Leaf area and nitrogen concentration increased from the bottom to the top of the canopy, while SLA decreased. Positive correlations between biomass production and abaxial stomatal density, as well as between biomass production and nitrogen concentration were found. A principal component analysis (PCA) showed that genotypes belonging to the same taxon had similar anatomical characteristics, and genotypes of the same section also showed common leaf characteristics. However, Wolterson (P. nigra) differed in anatomical leaf characteristics from other genotypes belonging to the same section (section Aigeiros). Hybrids between the two sections (Aigeiros × Tacamahaca) expressed leaf characteristics intermediate between both sections, while their biomass production was low.

Anatomía foliar y del pecíolo de especies del género Rhus s. str. (Anacardiaceae)

Se describe la anatomía foliar y del pecíolo de 33 especies de Rhus s. str. con el objetivo de evaluar los atributos anatómicos que apoyen su clasificación infragenérica. Los resultados apoyan la clasificación infragenérica existente de Rhus s. str. El subgénero Rhus, con sistema vascular tipo I y pecíolo con más de diez capas de colénquima y médula amplia, se distingue del subgénero Lobadium. La sección Terebinthifolia se caracteriza por tener dos o cuatro elementos de vaso, vaina colenquimatos a rodeando los haces vasculares y fibras gelatinosas; mientras que la sección Styphonia presenta una cutícula gruesa (> 6 µm), células epidérmicas papilosas, dos capas de parénquima en empalizada y esclerénquima en xilema y floema. La presencia de esclerénquima en la sección Styphonia se correlaciona con la persistencia de las hojas. Seguramente algunos de los atributos foliares mencionados se originaron durante los procesos de radiación del género Rhus s. str. que tuvieron lugar en México.

Caracterização morfoanatômica de plântulas de <em>Gomphrena elegans</em> Mart. (Amaranthaceae)

Aiming to describe seedlings’ morphology and cotyledons and eophylls anatomy of Gomphrena elegans Mart., 100 seeds were put into plastic bags, with sand and fertilized soil (1:3), kept in the greenhouse under room conditions, with 50% shady and watered daily. Cotyledonous petiole and limb and seedlings eophylls were sectioned in median and border. They were then analyzed in transversal and paradermic sections. Seedlings initial morphology is epigeal-foliar, the root is axial, and hypocotyls and epicotyl are reddish. Venation is of pinnate type, camptodrome and brochidrodome in cotyledons and eophylls. Petiole and leaf show uniseriated epidermis with cells of varied sizes and anomocytic stomata. Druses of calcium oxalate occurred in leaves and petiole. Dorsiventral mesophyll shows one palisade parenchyma layer and several lacunary ones.

Anatomical relations of the leaves in strawberry

In the present study histology of the leaves of strawberry (Fragaria ananassa Duch.) variety Elsanta was the objective, which has been performed with the beginning of seedling stage, cotyledons, primary leaves and later true leaves, first cataphyll of the runner shoot as well as the bracteoles of the inflorescence. Structures of the leaf blade, the upper and lower epidermis, the petiole have been also observed. The leaf blade of cotyledons already contains a typical palisade as well as spongy parenchyma tissues, i.e. being bifacial showing a structure similar to that of the true leaf. However, the petiole displays differences from the true leaf. There are a narrow (4-5 layer) primary cortex and a tiny central cylinder. Primary leaves bear already hairs on the adaxial surface and the transporting tissue-bundles are recognised in cross sections having a "V" shape. The first true leaf composed by three leaflets is of a simple structure showing characters reminding of cotyledons and primary leaves. Leaves of intermediate size continue to grow, whereas their inner anatomy changes dramatically. In the central region of the leaflets, near to the main vein, a second palisade parenchyma appears, further on, transporting tissue bundles are branching in the petiole. Collenchyma tissues enhance the stiffness and elasticity of the petiole. Older true leaves develop thick collenchyma tissues around the transporting bundles being represented by increasing numbers. The doubled palisade parenchyma layers of the leaf blades are generally observed. The cataphylls of the runners have a more simple structure, their mesophyll is homogenous, no palisade parenchyma appears. It is evident that leaves grown at successive developmental stages are different not only in their morphological but also anatomical structure. There is a gradual change according to the developmental stage of the leaves.

Morfoanatomia foliar de Palicourea longepedunculata Gardiner (Rubiaceae)

O gênero Palicourea - tribo Psychotrieae - compreende cerca de 200 espécies e destaca-se por apresentar alcalóides indólicos muitas vezes tóxicos para bovinos. O objetivo do presente trabalho foi contribuir para o conhecimento da família Rubiaceae, enfatizando os aspectos da morfoanatomia foliar de Palicourea longepedunculata. O material foi coletado na Reserva Florestal Mata do Paraíso (RFMP), município de Viçosa, Minas Gerais, e amostras-testemunha foram depositadas no herbário VIC. Folhas provenientes do quarto nó foram fixadas em FAA50 e conservadas em etanol 70%. Seções transversais e longitudinais do pecíolo e da lâmina foliar foram obtidas em micrótomo de mesa para montagem de lâminas permanentes, conforme metodologia usual. As folhas são simples, opostas, inteiras, ovais lanceoladas, dorsiventrais e hipoestomáticas. A epiderme do pecíolo e da lâmina foliar é uniestratificada, papilosa na face adaxial da folha e recoberta por cutícula delgada. Os estômatos são paracíticos e ocorrem no mesmo nível das demais células epidérmicas. O mesofilo é constituído por uma camada de parênquima paliçádico e de várias de parênquima lacunoso. Na face adaxial e abaxial da nervura mediana e no bordo da lâmina observa-se colênquima subepidérmico. Um feixe vascular do tipo colateral, em forma de "U", distribui-se ao longo do pecíolo e da nervura mediana, acompanhado, invariavelmente, por dois feixes menores localizados lateralmente. No córtex do pecíolo e da nervura mediana observa-se aerênquima. As características anatômicas seguem o padrão descrito para as Rubiaceae, e algumas delas são interpretadas como adaptações a ambientes úmidos e sombreados no qual a espécie ocorre.

Leaf Structure of Tobacco In Vitro Grown Plantlets as Affected by Saccharose and Irradiance

Tobacco plantlets were cultured in vitro under high (200 µmol m−2 s−1) or low (60 µmol m−2 s−1) irradiance with or without saccharose in the medium. Light microscopy and image analysis were used to evaluate the effect of these culture conditions on leaf anatomy. Addition of saccharose resulted in thicker leaves (all leaf layers) and larger mesophyll cells under both growth irradiances. Various irradiance affected leaf anatomy differently when plantlets had been cultivated in presence or absence of saccharose in the medium. While under high irradiance in presence of saccharose leaf thickness and number of chloroplasts per cell section were increased, plantlets grown under high irradiance in absence of saccharose had thinner leaves and less chloroplasts per cell section. The changes were more pronounced in palisade parenchyma layer.

The paraveinal mesophyll: a specialized path for intermediary transfer of assimilates in legume leaves

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999 The distance between sites of synthesis of assimilates and the site of phloem loading can be large, and specialized leaf cell layers such as the paraveinal mesophyll (PVM) might act to enhance the efficiency of transport. A number of techniques were used to analyse PVM of legume leaves with respect to a hypothesized function in transfer of assimilates between tissues. Of 39 legume species examined, PVM was found in 22. Leaves of all PVM-containing species had multiple palisade parenchyma layers, while non-PVM species generally had only one distinct palisade layer. Morphometric analysis identified a significant correlation between PVM presence and greater numbers of palisade cells per unit leaf surface area. Comparison of photosynthetic rates of four PVM and four non-PVM species showed the PVM species had higher rates on a leaf area basis than all but one of the non-PVM species. Microautoradiography of 14CO2 pulse–chase studies in soybean demonstrated PVM is an intermediary tissue in transfer of assimilates to vascular bundles. In addition, PVM cells but not mesophyll cells, were enriched in a sucrose binding protein previously found to be associated with sucrose-transporting tissues. The structural, positional and transport data support the hypothesis that the PVM acts as a transport pathway between the vascular system and photoassimilatory cells of the leaf, and has probably evolved to overcome diffusion limitations imposed by multiple palisade layers.