Abstract: The concentration of essential mineral nutrients in the edible portion of plants such as grains may affect the nutritional value of these foods, while concentrations of toxic minerals in the plant are matter of food safety. Minerals taken up by the roots from soils are normally redirected at plant nodes before they are finally transported into developing seeds. However, the molecular mechanisms involved in this process have not been identified so far. Herein, we report on a transporter (Lsi6) responsible for the redirection of a plant nutrient at the node. Lsi6 is a silicon transporter in rice (Oryza sativa), and its expression in node I below the panicles is greatly enhanced when the panicle is completely emerged. Lsi6 is mainly localized at the xylem transfer cells located at the outer boundary region of the enlarged large vascular bundles in node I. Knockout of Lsi6 decreased Si accumulation in the panicles but increased Si accumulation in the flag leaf. These results suggest that Lsi6 is a transporter involved in intervascular transfer (i.e., transfer of silicon from the large vascular bundles coming from the roots to the diffuse vascular bundles connected to the panicles). These findings will be useful for selectively enhancing the accumulation of essential nutrients and reducing toxic minerals in the edible portion of cereals.

Abstract: Vascular cambium, a type of lateral meristem, is the source of secondary xylem and secondary phloem, but little is known about the molecular mechanisms of its formation and development. Here, we report the characterization of an Arabidopsis thaliana gain-of-function mutant with dramatically increased cambial activity, designated high cambial activity2 (hca2). The hca2 mutant has no alternative organization of the vascular bundles/fibers in inflorescence stems, due to precocious formation of interfascicular cambium and its subsequent cell division. The phenotype results from elevated expression of HCA2, which encodes a nuclear-localized DNA binding with one finger (Dof) transcription factor Dof5.6. Dof5.6/HCA2 is preferentially expressed in the vasculature of all the organs, particularly in the cambium, phloem, and interfascicular parenchyma cells of inflorescence stems. Dominant-negative analysis further demonstrated that both ubiquitous and in situ repression of HCA2 activity led to disruption of interfascicular cambium formation and development in inflorescence stems. In-depth anatomical analysis showed that HCA2 promotes interfascicular cambium formation at a very early stage of inflorescence stem development. This report demonstrates that a transcription factor gene, HCA2, is involved in regulation of interfascicular cambium formation and vascular tissue development in Arabidopsis.

Abstract: The plant vascular system provides transport and support capabilities that are essential for plant growth and development, yet the mechanisms directing the arrangement of vascular bundles within the shoot inflorescence stem remain unknown. We used computational and experimental biology to evaluate the role of auxin and brassinosteroid hormones in vascular patterning in Arabidopsis. We show that periodic auxin maxima controlled by polar transport and not overall auxin levels underlie vascular bundle spacing, whereas brassinosteroids modulate bundle number by promoting early procambial divisions. Overall, this study demonstrates that auxin polar transport coupled to brassinosteroid signaling is required to determine the radial pattern of vascular bundles in shoots.

Abstract: It has been suggested that LeFRK2, the major fructose-phosphorylating enzyme in tomato plants, may be required for stem xylem development. Yet, we do not know if this enzyme affects the development of individual vessels, whether it affects water conductance, or whether it affects phloem development and sugar transport. Here, we show that suppression of LeFRK2 results in a significant reduction in the size of vascular cells and slows fiber maturation. The vessels in stems of LeFRK2-antisense plants are narrower than in WT plants and have thinner secondary cell walls. Although the cambium produces rounded secondary vessels, these vessels become deformed during the early stages of xylem maturation. Water conductance is then reduced in stems, roots, and leaves, suggesting that LeFRK2 influences xylem development throughout the entire vascular system. Interestingly, the build-up of positive xylem pressure under static (no-flow) conditions was also decreased. Suppression of LeFRK2 reduced the length and width of the sieve elements, as well as callose deposition. To examine the effect of LeFRK2 suppression on phloem transport, we created triple-grafted plants in which a portion of the wild-type stem was replaced with an antisense interstcok, and compared the contents of the transported sugar, sucrose, in the different portions of these stems. Sucrose contents above and within the LeFRK2-antisense interstock were significantly higher than those below the graft. These results show that the antisense interstock restricted the downward movement of sucrose, suggesting that LeFRK2 is required for both phloem and xylem development.

Abstract: Histochemical staining using vanillin-HCl is a potential tool to identify the site-specific accumulation of catechins in the tea plant (Camellia sinensis (L.) O. Kuntze). Using this technique revealed that catechins existed ubiquitously in all inspected tissues in young tea leaf, but the distribution was concentrated in the vascular bundle and palisade tissue, whereas the large parenchyma cells of the main vein contained lower amounts of catechins. At the subcellular level, catechins were located mainly in the chloroplasts of mesophyll cells and in the vessel wall. In young stems, catechins could be detected in most cells except the parenchyma cells of the pith and the cortex, whereas, in roots, catechins could be detected only in those cells surrounding the pericycle. Moreover, differing distributions of catechins were found in calluses cultivated in darkness and light. On the basis of HPLC analyses, six main types of catechins were present in tea leaves, stems, calluses, and chloroplasts; however, roots contained only epicatechin.

Abstract: The foliar structure of 44 species of Myrtoideae Nied. (Myrtaceae) was described to characterise the anatomy of the leaves in this subfamily and also to recognise particular features in each genus and/or subtribe. In the present study, nine genera of the subtribe Myrtinae, five genera of the subtribe Myrciinae and eight genera of the subtribe Eugeniinae were examined. All of them have dorsiventral and hypostomatic leaves, with stomata slightly protruded in relation to other epidermal cells; the leaves also present secretory cavities, idioblasts containing druses and vascular bundles with phloem on both adaxial and abaxial sides. Some surface features have diagnostic value for all genera of these three subtribes, such as the percentage of palisade parenchyma, the presence or absence of an adaxial hypodermis, the occurrence of an extension to the vascular bundle sheath, and the shape and position of the vascular system of the midrib. These features are described for each of the species studied and the results are discussed in a taxonomical context.

Abstract: The activities and localizations of superoxide dismutases (SODs) were compared in root and stem nodules of the semi-aquatic legume Sesbania rostrata using gel-activity assays and immunogold labelling, respectively. Nodules were fixed by high-pressure freezing and dehydrated by freeze substitution. Stem nodules showed more total and specific SOD activities than root nodules because of the presence of chloroplastic CuZnSOD. Most of the total SOD activity of stem and root nodules resulted from 'cytosolic' CuZnSOD, localized in the cytoplasm and chromatin, and from MnSOD in the bacteroids and in the mitochondria of vascular tissue. FeSOD was present in nodule plastids and in leaf chloroplasts, and was found to be associated with chromatin. Superoxide production was detected histochemically in the vascular bundles and in the infected tissue of stem and root nodules, whereas peroxide accumulation was observed in the cortical cell walls and intercellular spaces, as well as within the infection threads of both nodule types. These data suggest a role of CuZnSOD and FeSOD in protecting nuclear DNA from reactive oxygen species and/or in modulating gene activity. The enhanced levels of CuZnSOD, MnSOD and superoxide production in vascular bundle cells are consistent with a role of CuZnSOD and superoxide in the lignification of xylem vessels, but also suggest additional functions in coping with superoxide production by the high respiratory activity of parenchyma cells.

Abstract: In NADP-malic enzyme (NADP-ME) type C4 plants, MC chloroplasts have well-developed grana, whereas BSC chloroplasts are generally characterized by highly reduced grana. In the previous study, salt t...

Abstract: 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 we...

Abstract: Andira legalis (Vell.) Toledo is a legume shrub widespread along the sandy plains of the Brazilian coast. It occurs both shaded, in forest habitats, or exposed to full sunlight, in the vegetation islands growing on sand deposits. Previous studies reported a high range of morpho-physiological variation for this species along a geographical gradient. This study compared leaf morphology and anatomy of A. legalis in two distinct but adjacent light environments: a dense forest (shaded) and a scrub of Palmae (exposed). We studied the amplitude of variation for these traits within a small (0.5 ha) geographical area. Leaf anatomy parameters were measured for five leaves collected from five plants in each habitat. The parameters measured were leaf and mesophyll thickness, thickness of the outer periclinal cell wall, thickness of the adaxial and abaxial epidermis and vascular bundle transversal section area, and also common epidermal cells, stomata and trichome density. Leaf morphology parameters were obtained from five leaves of each of 20 plants in each site. Dry and fresh weights were measured to obtain leaf specific mass and succulence. All anatomy and morphology parameters, except trichome density, were significantly higher for the sun-exposed plants. Less expected, however, was the marked qualitative difference between exposed and shaded plants: in the former the mesophyll had a unilateral symmetry (i.e., the whole mesophyll occupied by photosynthetic tissue), whereas in the latter there was a dorsiventral symmetry (i.e., partly palisade and partly spongy parenchyma). Such amplitude of variation shows that even within a small geographic area A. legalis has a broad ecological plasticity.

Abstract: Photosynthesis and associated signalling are influenced by the dorso-ventral properties of leaves. The degree of adaxial/abaxial symmetry in stomatal numbers, photosyn- thetic regulation with respect to light orientation and the total section areas of the bundle sheath (BS) cells and the surrounding mesophyll (M) cells on the adaxial and abaxial sides of the vascular bundles were compared in two C4 (Zea mays (maize) and Paspalum dilatatum) and one C3 (Triticum turgidum (Durum wheat)) monocotyledonous species. The C3 leaves had a higher degree of dorso-ventral symmetry than the C4 leaves.Photosynthetic regulation was the same on each side of the wheat leaves, as were stomatal numbers and the section area of the BS relative to that of the M cells (BS/M section area ratio). In contrast, photo- synthetic regulation in maize and P. dilatatum leaves showed a marked surface-specific response to light orienta- tion. Compared to the adaxial sides of the C4 monocotyle- donous leaves, the abaxial surfaces had more stomata and the BS/M section area ratio was significantly higher. Differ- ences in dorso-ventral structure, particularly in Kranz anatomy, serve not only to maximize photosynthetic capac- ity with respect light orientation in C4 monocotyledonous leaves but also allow adaxial and abaxial-specific signalling from the respective M cells.

Abstract: We made drill holes in the stems of six Cycas species and used a standard microtechnique and microscopy methods to determine the structural responses of the soft-wooded, parenchymatous (manoxylic) stems after 2 and 12 months of recovery. We also injected an aqueous stain to one plant per species to determine the transverse hydraulic pathways among the discrete tissue categories. Expanding secondary tissue decay and insect larva infestations were evident in some wounds after 2 months. Wounds that lacked the secondary complications had recovered as a result of wound periderm after 2 months. Large areas of secondary rotting after 2 months were bounded by wound periderm after 12 months. The wound periderm formed a thick, leathery phellem (cork) that was continuous across cortex, vascular, and pith tissues. The six species represent a range in ease of horticultural management, yet the form of recovery from the wounds was similar for all species. Mucilage exudation from cut surfaces was copious, and species differences in volume of mucilage were also not related to extent or form of recovery from the wounds. Stain injected into the hole moved longitudinally and laterally within a vascular cylinder to adjacent vascular cylinders and to the cortex by way of persistent leaf traces. Results indicate a transverse hydraulic connection among the concentric vascular cylinders and leaf traces that extend into the cortex. Moreover, the succulent nature of this manoxylic stem is highly susceptible to secondary infection whenever the protective bark is removed or the internal tissues are injured. Therefore, use of prophylactic treatments to minimize the risk of secondary complications is warranted whenever pruning or amputation of adventitious shoots for propagation remove the protective bark from the succulent cortex tissue.

Abstract: We examined the anatomy of roots, rhizomes, leaves, and scapes of Cyperus odoratus L., Oxycaryum cubense (Poep. & Kunth) Lye, and Pycreus macrostachyos (Lam.) Raynal (Cyperaceae-Poales) from temporary lakes in the semi-arid region of Bahia in order to characterize the anatomy and examine structural adaptations to amphibious lifestyle. All species had roots with uniseriate epidermal cells, cortex with exoderm and air canals. The rhizomes had amphivasal or collateral vascular bundles in the vascular cylinder. The leaves had uniseriate epidermal cells with external periclinal cell walls thicker than the inner walls, stomata on the abaxial leaf surface, chlorenchyma alternating with air canals, and collateral vascular bundles. The scapes had uniseriate epidermal cells, fibrous groups distributed peripherally, alternating with chlorenchyma, air canals, and collateral vascular bundles. Oxycaryum cubense differs from Cyperus odoratus and Pycreus macrostachyos by having roots with long hairs; rhizomes and stolons with collateral vascular bundles; leaf blades with acute margins, and lacking Kranz structures in leaves and scapes. Anatomic characters such as the presence of large air canals principally in the roots, bulliform cells on the adaxial face of the leaf epidermis, hypodermis, reduced numbers of xylem vascular elements and little lignification of the cell walls of the different plant organs are considered important features in the adaptation of these amphibious plants that inhabit temporary lakes in the semi-arid region of Bahia state.

Abstract: The gross anatomical characteristics of 5 parasitic plant species, viz., Cuscuta reflexa Roxb. (Cuscutaceae), Orobanche aegyptiaca Pers. (Orobanchaceae), Korthalsella opuntia (Thomb.) Merrill, Viscum album L., and Viscum cruciatum Seib. Ex. Spreng. (Viscaceae) were investigated. The vascular bundles of all these parasitic plants were less developed having poorly developed phloem but well developed xylem. The most interesting features were the presence of terminal sclereids in Viscum cruciatum and brachysclereids in Korthalsella opuntia. Terminal sclereids have not been reported previously in the genus. These parasitic species show variation in the invasiveness of endophytic tissue of haustorium into the host vascular tissue. Haustorium of Cuscuta reflexa forms connection to the phloem of the host. The haustorium was consisting of few threads of xylem and phloem which penetrate only to the phloem tissue of the host. In Korthalsella opuntia and Viscum cruciatum haustoria form connection to the xylem of the hosts. The haustorium of Korthalsella opuntia is well developed and surrounds the host xylem in the form of cup.

Abstract: The nutrient release patterns and decomposing rates of wheat and rapeseed straws were studied in rice fields.The straws were wrapped in net nylon bags and mulched to the fields.During the decomposing process,straw samples were taken on schedule,and were observed using electron microscope for its tissue structural images of cross sections.Results reveal that the decomposing rates of the two straws are fast at the beginning,and then slowly decrease with time.During the rice growth and development season which is about 100 d,the cumulative decomposing rates are 66.18% and 55.62% for wheat straw and rape shoot,respectively.Release rates of the nutrients of the straws are different;the K release rate is considerably greater than the rates of P and N releases.Within the first 10 d,about 98.92% of K is released from wheat straw,and 98.74% from rape shoot.Based on the electron microscopic observations,there is not noticeable tissue damage of the wheat straw at the first 50 d,and after 50 d,the tissue damage mainly take place at the parenchyma cells and its surrounded vascular bundles,while the cuticle and mechanic tissues seem not damaged significantly.For rape shoot,however,the mechanic tissue damage is observed within the first 10 d when the vascular bundle cambium outside of the secondary xylem,phloem fiber,epidermal parenchyma and cuticle are all broken.These results further demonstrate that K in the straw is water extractable and readily available to plant.Therefore,amount of K in the straws should be subtracted from the recommended fertilization,while rates of N and P should be maintained in the fertilization at early crop growth stages.

Abstract: The existence of major vertical gradients within the leaf is often overlooked in studies of photosynthesis. These gradients, which involve light heterogeneity, cell composition, and CO2 concentration across the mesophyll, can generate differences in the maximum potential PSII efficiency (F V/F M or F V/F P) of the different cell layers. Evidence is presented for a step gradient of F V/F P ratios across the mesophyll, from the adaxial (palisade parenchyma, optimal efficiencies) to the abaxial (spongy parenchyma, sub-optimal efficiencies) side of Quercus coccifera leaves. For this purpose, light sources with different wavelengths that penetrate more or less deep within the leaf were employed, and measurements from the adaxial and abaxial sides were performed. To our knowledge, this is the first report where a low photosynthetic performance in the abaxial side of leaves is accompanied by impaired F V/F P ratios. This low photosynthetic efficiency of the abaxial side could be related to the occurrence of bundle sheath extensions, which facilitates the penetration of high light intensities deep within the mesophyll. Also, leaf morphology (twisted in shape) and orientation (with a marked angle from the horizontal plane) imply direct sunlight illumination of the abaxial side. The existence of cell layers within leaves with different photosynthetic efficiencies makes appropriate the evaluation of how light penetrates within the mesophyll when using Chl fluorescence or gas exchange techniques that use different wavelengths for excitation and/or for driving photosynthesis.

Abstract: The research made on the anatomy of the Hedera helix vegetative organs have highlighted some features characteristic of the epidermis, collenchymas and assimilator tissue of the leaves and fertile and sterile stems. A thick cuticle covers the epidermis. Following the felogen activity, the epidermis is broken at the sterile stems comparative with the fertile stems. Tectorial multi-cell hairs are in the epidermis of both stem types. The cortex is multi-layered and it can be differentiated in two zones: external and internal cortex. The external cortex has done by the 4-5 collenchymatous cell layers with calcium oxalate crystals in numerous cells. The internal cortex has done by 5-7 cell layers with thin walls and many secretive ducts close to the pericycle. In the central cylinder were found 20-35 vascular bundles from open collateral type, with phloem outside and xylem inside. The medulla made up of isodiametric cells with thin walls. The leaves are hypostomatic type with tectorial hairs and the mesophyll is bifacial. Into the mesophyll are vascular bundles of collateral type with the xylem outside and phloem inside. In some cells of mesophyll leaves are crystals of calcium oxalate and secretive ducts into the median nervure.

Abstract: In order to understand the distribution and structure of vascular tissue in the peach fruit,observation of the branches system and distribution of vascular bundles was taken with the normal paraffin section and peach(Prunus persica 'Okubao')fruit was used as materialThe results showed that:Vascular bundles in peach fruit can be divided into three types,main vascular bundle,branch vascular bundle and fibrous vascular bundleMain vascular bundles include embryo vascular bundle,endocarp vascular bundle and mesocarp vascular bundle(ventral bundle and dorsal bundle,and vascular bundles on endocarp from pedicel)Their functions are that transport nutrition to the seed,endocarp and the mesocarp respectivelyEmbryo vascular bundle has developed phloem and tertiary structure;Vascular bundles with developed phloem are annularly distributed in the endocarp;Ventral bundle and dorsal bundle are thick,both of them have a majority of branches and developed phloem and xylemBranch vascular bundles and fibrous vascular bundles mainly distribute in the mesocarpThe cavity is observed in phloem of fibrous vascular bundle in the mesocarp and it enlarges with the fruit growthThe structures of vascular bundles accommodate to their functionsIt can be speculated that seed and endocarp mostly need organic nutrition and the mesocarp needs organic nutrition,mineral nutrition and water

Abstract: Smilax goyazana is a dioicous species occurring very commonly in the Brazilian cerrado vegetation. Leaves from male and female plants were compared in size and anatomical structure. No differences in size were found. Female plants presented higher stomatal density than the male ones. All other qualitative and quantitative parameters did not show differences related to sex. The leaf blade is amphistomatous. Only spongy mesophyll is present. In the midrib, there are three vascular bundles that fuse into one bundle in about the second third of the foliar length. Idioblasts containing calcium oxalate occur randomly in the petiole and leaf blade. No starch or tannins were evidenced. Nervation is acrodromous. S. goyazana presents structures similar to other Smilacaceae, however, in the whole, it presents distinctive characteristics from other species of the genus.

Abstract: Anatomical observations of the petiole and lamina of Mammea L. (Clusiaceae, Kielmeyeroideae) show extensive variation. All species have a complex folding pattern of the vascular bundle within the petiole, differing from most of the patterns found in the rest of the family. Except for the species found in the Neotropics and Africa, the laminas of almost all species contain fibers not immediately associated with the vascular tissue—a unique feature in the Clusiaceae. Fiber motifs range from bundles originating within the petiole, sheets forming an almost contiguous layer, to fibers with various patterns of organization derived from the secondary veins. Species groups based on fiber motif are recognized, and these correlate with other anatomical and morphological characters.

Abstract: Foliage damage as a result of individual freeze events is a major limitation to the expansion of bahiagrass (Paspalum notatum) pastures and hay production in Southeastern USA. Greater tolerance to such freeze events would allow production deeper into the fall and winter and allow expansion of this species into colder regions. While it has been reported that small cells are more tolerant to freeze damage, this possibility has not been explored in bahiagrass. Specifically, the hypothesis was examined that xylem vessels with smaller diameter in the midrib of leaves are associated with freeze tolerance among bahiagrass genotypes. Vascular bundle diameter was also measured as a possible index of xylem cell size. A total of eight bahiagrass genotypes were eventually studied representing four freeze-sensitive and four freeze-tolerant lines. There was a clear distinction in xylem cell size between the freeze-sensitive and the freeze-tolerant lines. The freeze-tolerant genotypes had xylem element cells that were significantly smaller than the freeze-sensitive genotypes. Averaged across three leaf positions and all genotypes, the xylem element diameter for the freeze-sensitive lines was 222 μm and for the freeze-tolerant lines was only 164 μm. A similar difference was observed in overall vascular bundle diameter with freeze-sensitive lines having a mean of 1168 μm and the freeze-tolerant lines a mean of 917 μm. These results indicated that the diameter of the xylem cells in the vascular midrib of bahiagrass may be an important variable influencing the sensitivity among genotypes to freeze damage.

Abstract: Were analized the rhizomes of Bulbostylis paradoxa Ness, Cyperus giganteus Vahl, C. odoratus L., Fuirena umbellata Rottb. and Hypolytrum schraderianum Ness. The primary body results from activity of primary meristems and primary thickening meristem (PTM). Secondary growth occurs too, due to the activity of the secondary thickening meristem (STM). Collateral vascular bundles are formed from procambium and MEP in H. schraderianum, and amphivasal bundles in the other species. However, all of the vascular bundles having protophloem and protoxylem are originated from procambium. Phloem and xylem are formed from MES in a single vascular tissue. Vessel elements were present in the most of the stems in primary and secondary growth, exception to H. schraderianum that has only tracheids in the last one; this information supports the occurrence of secondary growth in Cyperaceae. The vessel elements show a great morphological variation; generally, vessel elements from the primary growth, are longer and tip of vessel elements are present. The vessel elements from secondary growth are shorter and show tip of vessel elements and branchings.

Abstract: In order to investigate the characteristics of vascular bundle system in spikes and caryopsis of wheat,the structure,number,development of vascular bundle system in spikes and caryopsis of medium-gluten wheat(Tritium aestivum L.) Yangmai 16 and their relationship were observed via the optical microscope,electron microscope and fluorescence microscope,etc.The main results were as follows:(1) From 8th day to 28th day after flowering,the middle vascular bundle in spikes were dyed red deeply reaction to TTC,later,lighter;The middle vascular bundle in spikes were dyed reaction to I2-KI from 4th day to 24th day after flowering,later,little dyed.(2) The vascular bundle in caryposis abdomen appeared not entirely formed within 6 days after flowering,the fully differentiated vascular bundle formed at 12th day after flowering.From the 15th to 30th day after flowering,it matured completely and played an important roles in substance transport,its transport functions lost at about 36th day after flowering.(3) At the 19th day after flowering,some SEs had typical CC and SECC ccomplex formed.There were big thin-wall cells around it.Compared to SE,the CC or thin-wall cell had larger volume,thicker cytoplasm and denser mitochondrion;At the 32th day after flowering,the outer shape of thin-wall cells took on abnormity,many cell walls extruded or concaved,the cell nucleus disjointed,the numbers of mitochondrion decreased.(4) The vascular bundles of rachis proglottis were arranged with two annulus from outer to inner.The vascular bundles in outer annulus in the stem brim were smaller,while in the inner annulus bigger,and surrounded by the around basis tissues.(5) The number of large vascular bundles in the rachis proglottis decreased form base to top,that of top and base decreased less,but that of middle decreased more,while the small vascular bundles was the reverse.(6) There were 12~13 vascular bundles in rachilla base,6~7 in the first flower base of every spikelet,5~6 in the second flower base,3~4 in the third or fourth flower base,3 at the fifth or upwards flowers.

Abstract: The ontogeny of Ctenitis melanosticta (Kunze) Copel. and Diplazium expansumWilld. fronds was studied with the main goals to determine if continuous and discontinuous sheaths (bands in tranverse section) have the same origin in parenchyma cells. Frond ontogeny was followed from the crozier (fiddlehead) to the mature frond. Differentiation of the sheath begins during the crozier stage a few centimeters from the base of the stipe. As seen in transverse section, band differentiation occurs in the innermost parenchyma cells of the ground tissue, which surrounds the vascular strands of each vascular bundle of a multiple leaf trace. Based on its position and origin, it is named circumendodermal band (sheath in three dimensions) and the discontinuous form is designated “perforated sheath”. The circumendodermal band and the endodermis arise from parenchyma cells. Both the continuous circumendodermal band in C. melanosticta and the discontinuous circumendodermal band in D. expansum differentiate from ground parenchyma cells surrounding each vascular bundle. In the lamina of C. melanosticta, the circumendodermal band differentiates when frond is fertile and in the lamina of D. expansum, it never differentiates. The circumendodermal band traits are not related to plant size, but to number of vascular strands. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract: 1 , STĂNESCU IRINA 2 , CACHIŢĂ-COSMA DORINA 1 Abstract. In a histo-anatomic analysis of the exemplars of Sedum telephium L. ssp. maximum (L.) Krock. from nature and in vitro, the root presents a secondary structure, protected by a quite thin peridermis. The central cylinder bears vascular bundles, less numerous in vitro; the phloemic elements are grouped in small isles in both in vitro and from nature exemplars. The stem presents a few vascular bundles, where the xylem vessels bear thickened and lignified walls. The petiole reveals three vascular bundles. The foliar limb is amphistomatic, bearing anizocytic stomata in both in vitro and from nature exemplars, with homogenous mesophyll.