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Stem and root of Lindera erythrocarpa were described and compared in the wood anatomical aspects. Root wood ap-pearedto differ from stem wood in the qualitative features of growth ring boundary, extraneous materials in vessel ele-ment and ray parenchyma cell, outline of ray, and sheath cell. In the quantitative features, there were differences be-tween these two tissues in vessels per square millimeter, tangential diameter of vessel lumina, length of vessel element, and width of ray. These wood anatomical differences between stem above ground and root below ground were thought to be attributed to their different growth environments.

High-yielding, stress-tolerant grass crops are essential to meet future food and energy demands. Efforts are underway to engineer improved varieties of the C3 cereal crop rice by introducing NADP-malic enzyme C4 photosynthesis using maize as a model system. However, several modifications to the rice leaf vasculature are potentially necessary, including the introduction of suberin lamellae into the bundle sheath cell walls. Suberized cell walls are ubiquitous in the root endodermis of all grasses, and developmental similarities are apparent between endodermis and bundle sheath cell walls. Nonetheless, there is considerable heterogeneity in sheath cell development and suberin composition both within and between grass taxa. The effect of this variation on physiological function remains ambiguous over forty years after suberin lamellae were initially proposed to regulate solute and photoassimilate fluxes and C4 gas exchange. Interspecies variation has confounded efforts to ascribe physiological differences specifically to the presence or absence of suberin lamellae. Thus, specific perturbation of suberization within a uniform genetic background is needed, but, until recently, the genetic resources to manipulate suberin composition in the grasses were largely unavailable. The recent dissection of the suberin biosynthesis pathway in model dicots and the identification of several promising candidate genes in model grasses will facilitate the characterization of the first suberin biosynthesis genes in a monocot. Much remains to be learned about the role of bundle sheath suberization in leaf physiology, but the stage is set for significant advances in the near future.

Objetivou-se com este trabalho avaliar alterações nos caracteres anatômicos e morfológicos da folha (bainha e lâmina) e do caule de Brachiaria brizantha tratada com o regulador de crescimento trinexapac-ethyl. O delineamento experimental utilizado foi o completamente ao acaso, com duas doses do trinexapac-ethyl (0,00 e 0,75 kg ha-1) e cinco repetições. Cinquenta dias após a aplicação dos tratamentos, amostras do terço médio da bainha, da lâmina da segunda folha completamente expandida e do entrenó do caule abaixo da inserção da bainha foliar foram coletadas para a determinação de características morfológicas, como altura de planta, comprimento e diâmetro de entrenó, comprimento da bainha, comprimento e largura da folha. Para avaliação das características anatômicas, foram realizados cortes transversais da folha e do caule e cortes longitudinais do caule, em micrótomo de mesa, e corados com fuccina e azul de astra preparadas em lâminas semipermanentes. As imagens obtidas foram digitalizadas usando-se microscópio de luz acoplado a câmera digital e conectado a um computador. Para obtenção das medidas de área e medidas lineares foi utilizado o software Image Pro-Plus. Os dados foram submetidos à análise estatística, pelo teste F a 5% de probabilidade. O regulador de crescimento promoveu redução do comprimento do limbo foliar, do entrenó, da bainha e da altura de plantas. Por outro lado, no limbo foliar, o trinexapac-ethyl aumentou a espessura da lâmina foliar, da área das células da bainha e da área do mesofilo em B. brizantha. The objective of this work was to evaluate changes in the anatomical and morphological characters of leaf (sheath and mesophyll), and stem of Brachiaria brizantha when treated with the plant growth regulator trinexapac-ethyl. The experimental design was completely randomized, with two doses of trinexapac-ethyl (0.00, 0.75 kg ha-1) and five repetitions. Fifty days after treatment application, samples from the middle third of the sheath, blade of the second fully expanded leaf and stem internode below the leaf sheath insertion were collected for the determination of morphological characteristics, such as plant height, internode length and diameter, sheath length and leaf length and width. For evaluation of the anatomical features, transverse cuts of leaves, stem and sheath and longitudinal cuts of the stem were made, in table microtome and stained with fuchsin and astra blue and prepared into semi-permanent slides. The images obtained were scanned using a light microscope coupled to a digital camera and connected to a computer. To obtain area and linear measures, the software Image Pro-Plus was used. The data were subjected to statistical analysis, using the F test at 10% probability. The growth regulator reduced the length of tho the leaf blade, internode and sheath and also plant height. On the other hand, trinexapac-ethyl increased leaf blade thickness sheath cell and mesophyll areas, providing anatomical and morphological changes in B. brizantha.

Leaves harvested from unhardened and cold-hardened rye (Secale cereale L. 'Puma') were examined by electron microscopy. Upon cold acclimation,m mestome sheath cell walls were thickened asymmetrically toward the vascular bundle, while epidermal cell walls were thickened asymmetrically toward the leaf surface. Cell wall deposits were osmiophilic and lamellar in structure. These characteristics suggest deposition of lipid polymers. Epicuticular waxes also increased in thickness and changed from a rodlike to a platelet-like structure upon cold acclimation. Thickening of the epidermasl and mestome sheath cell walls during cold acclimation is thought to decrease injury caused by freezing or desiccation.

Following the Oschman and Wall technique, electron-dense structures (EDS) were found on unstained, unosmicated membranes of squid giant synapse axons. These densities contain high concentrations of calcium and phosphorus as identified by energy dispersive X-ray analysis. Based on the signal strength, the quantity is significantly greater than that of other regions of the membrane or tissue spaces. The calcium EDS occur as plaques or globules along the axonic membrane, and small globules are found between sheath cell processes. EDS also occur at the synaptic site. These densities were correlated with the opacity change seen in giant axons. It is proposed that these structures represent sites where the calcium-binding protein found by other investigators has become nearly saturated with calcium.

The distribution of pit fields and plasmodesmata in the mestome-sheath cells of a wheat leaf has been determined by study of sections and partial macerates. Each bundle is approximately symmetrical about the sagittal plane and most plasmodesmata occur in the mestome sheath where its cells abut the metaphloem. Plasmodesmata are absent adjacent to xylem vessels, and the frequency of plasmodesmata declines sharply in cells that lie close to the sagittal plane. Calculations show that 1 cm(2) of leaf lamina has approximately 2x10(8) plasmodesmatal connections to the phloem of the longitudinal veins, and that 85% of these connections are to the late-maturing intermediate bundles that do not complete their differentiation until leaf growth is nearly finished. The phloem area of inner tangential wall of the mestome sheath amounts to 0.26 cm(2) per cm(2) of leaf area and plasmodesmata occupy 1.5% of this area.These anatomical facts are used to estimate the sugar flux across the inner-tangential wall of the sheath as 2x10(2) pmol s(-1) cm(2) sheath. Further analysis strongly suggests that this flux must cross the sheath by diffusion through the plasmodesmata, creating there a flux of 1.5x10(4) pmol s(-1) cm(-2) plasmodesma. These results are compared with data recently obtained for the transfer-cell/sieve-element boundary in Vicia and are found to be about one tenth of the flux in that system, the transfer being adequately driven by a concentration gradient of 50 μg cm(-3) of sugar across the sheath. Such a concentration gradient could be achieved by the photosynthetic activity of about 50 chloroplasts acting for about 2 min. The transverse veins that lack a mestome sheath are unlikely to account for more than 10% of the fluxes calculated here and have been ignored in the calculations. It is concluded that the symplastic pathway is the only possible one for assimilate traffic across the mestome sheath in wheat, and that diffusion down a gradient of sugar concentration from the chloroplasts to the sheath acts as the driving force. This suggestion is reinforced by analysis of the contributions of the larger and smaller veins to the water flux from the same square centimetre of leaf. This analysis shows that 99% of the water flux must exit from the xylem of the 7 large bundles, presumably through the apoplast, securing an effective separation between the inwardly directed flow of sugar (laoded symplastically chiefly through the small longitudinal bundles) and the outwardly directed, very much larger flux of water.

Regenerative therapy for degenerative spine disorders requires the identification of cells that can slow down and possibly reverse degenerative processes. Here, we identify an unanticipated wound-specific notochord sheath cell subpopulation that expresses Wilms Tumor (WT) 1b following injury in zebrafish. We show that localized damage leads to Wt1b expression in sheath cells, and that wt1b+cells migrate into the wound to form a stopper-like structure, likely to maintain structural integrity. Wt1b+sheath cells are distinct in expressing cartilage and vacuolar genes, and in repressing a Wt1b-p53 transcriptional programme. At the wound, wt1b+and entpd5+ cells constitute separate, tightly-associated subpopulations. Surprisingly, wt1b expression at the site of injury is maintained even into adult stages in developing vertebrae, which form in an untypical manner via a cartilage intermediate. Given that notochord cells are retained in adult intervertebral discs, the identification of novel subpopulations may have important implications for regenerative spine disorder treatments.