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Cores do Outono - Folda seca da Samambaia.
Ferns are vascular plants differing from lycophytes by having true leaves (megaphylls). They differ from seed plants (gymnosperms and angiosperms) in their mode of reproduction—lacking flowers and seeds. Like all other vascular plants, they have a life cycle referred to as alternation of generations, characterized by a diploid sporophytic and a haploid gametophytic phase. Unlike the gymnosperms and angiosperms, the ferns' gametophyte is a free-living organism.
A fern is any one of a group of about 12,000 species of plants. Unlike mosses, they have xylem and phloem (making them vascular plants). They have stems, leaves, and roots like other vascular plants. Ferns do not have either seeds or flowers (they reproduce via spores).
By far the largest group of ferns are the leptosporangiate ferns, but ferns as defined here (also called monilophytes) include horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns. The term pteridophyte also refers to ferns (and possibly other seedless vascular plants; see classification section below). A pteridologist is a specialist in the study of ferns and lycophytes.
Ferns first appear in the fossil record 360 million years ago in the Carboniferous but many of the current families and species did not appear until roughly 145 million years ago in the late Cretaceous (after flowering plants came to dominate many environments).
Ferns are not of major economic importance, but some are grown or gathered for food, as ornamental plants, or for remediating contaminated soils. Some are significant weeds. They also featured in mythology, medicine, and art.
Vascular Plants of the Osa Peninsula, Costa Rica
sweetgum.nybg.org/science/projects/osa/
RA#16507 osa_02745
cross section: Nymphea leaf
common name: Waterlily
magnification: 100x
Berkshire Community College Bioscience Image Library
Both the upper (adaxial) and lower (abaxial) epidermis are uniseriate and contain chloroplasts. The air exposed adaxial epidermis is well cutinized and contain numerous stomata that open into large substomatal air chambers. The submerged abaxial epidermis has a very thin cuticle and lacks stomata. Dark staining slime glands are present on the abaxial surface.
Deep to the upper epidermis are several layers of tightly packed palisade mesophyll, the chief photosynthetic tissue of the leaf. Most of the leaf interior is occupied by a deeper zone of spongy mesophyll with large air spaces. Large red staining branched astroscleroids are abundant throughout the mesophyll.
Vascular bundles are centrally located with collaterally arranged xylem toward the adaxial surface and phloem to the abaxial surface. Particularly noticeable is an outer bundle sheath of large parenchyma cells. All vascular tissues are highly reduced except in the mid rib area where bundles with defined phloem, proto and meta xylem, and a protoxylem lacunae can be seen. Tannin rich parenchyma cells are occasionally associated with phloem of larger bundles.
The mid rib area is supported towards the abaxial surface by a wide wedge of supportive collenchyma.
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cross section: Young stem: Helianthus
common name: Sunflower
magnification: 40x
Berkshire Community College Bioscience Image Library
All vascular tissues in Helianthus are the product of primary growth. There are no signs of secondary growth (growth rings or lateral meristems) as might be seen in woody stems.
The uniseriate and cutinized epidermis contains large multicellular trichomes and occasional stomata.
The cortex consists of an outermost hypodermis of heavy walled collenchyma, a deeper layer of parenchyma and a deepest band of endodermis (starch sheath).
Within the stele the vascular bundles are arranged in a ring and separated from each other by wide medullary rays of parenchyma cells.
The collaterally arranged vascular bundles are almost entirely primary phloem and xylem. Each bundle consists of a large outer supportive cap of sclerenchyma fibers (phloem fiber cap), a deeper layer of primary phloem with well-defined sieve tubes and companion cells, and a deepest layer of primary xylem. In between the xylem and phloem, a narrow band of cambium may be seen. In some preparations, the highly lignified cells walls of xylem and mature sclerenchyma are stained red orange. These cells are dead at maturity and can also be distinguished by a heavy cell wall and absence of cytoplasm.
The center of the stem is occupied by a pith of parenchyma cells that contain numerous starch storing amyloplasts.
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cross section: human pancreas
magnification: 400x by phase contrast
hematoxylin eosin stain
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Golden Beach, Thassos.
Walking back to our end of the beach from Skala Potamias.
From Wikipedia -
Cuscuta (Dodder) is a genus of about 100-170 species of yellow, orange or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, recent genetic research by the Angiosperm Phylogeny Group has shown that it is correctly placed in the morning glory family, Convolvulaceae. The genus is found throughout the temperate to tropical regions of the world, with the greatest species diversity in subtropical and tropical regions; the genus becomes rare in cool temperate climates, with only four species native to northern Europe.
Old folk names include devil's guts, devil's hair, devil's ringlet, goldthread, hailweed, hairweed, hellbine, love vine, pull-down, strangleweed, angel hair, and witch's hair.
Dodder can be identified by its thin stems appearing leafless, with the leaves reduced to minute scales. From mid-summer to early autumn, the vines can produce small fruit that take the same color as the vine, and are approximately the size of a common pea. It has very low levels of chlorophyll; some species such as Cuscuta reflexa can photosynthesize slightly, while others such as C. europaea are entirely dependent on the host plants for nutrition.
Dodder flowers range in color from white to pink to yellow to cream. Some flower in the early summer, others later, depending on the species. The seeds are minute and produced in large quantities. They have a hard coating, and can survive in the soil for 5–10 years or more.
Dodder seeds sprout at or near the surface of the soil. While dodder germination can occur without a host, it has to reach a green plant quickly; dodder grows toward the smell of nearby plants. If a plant is not reached within 5 to 10 days of germination, the dodder seedling will die. Before a host plant is reached, the dodder, as other plants, relies on food reserves in the embryo; the cotyledons, though present, are vestigial.
Parasitism
After a dodder attaches itself to a plant, it wraps itself around it. If the host contains food beneficial to dodder, the dodder produces haustoria that insert themselves into the vascular system of the host. The original root of the dodder in the soil then dies. The dodder can grow and attach itself to multiple plants. In tropical areas it can grow more or less continuously, and may reach high into the canopy of shrubs and trees; in temperate regions it is an annual plant and is restricted to relatively low vegetation that can be reached by new seedlings each spring.
Dodder is parasitic on a very wide variety of plants, including a number of agricultural and horticultural crop species, such as alfalfa, lespedeza, flax, clover, potatoes, chrysanthemum, dahlia, helenium, trumpet vine, ivy and petunias, among others.
Dodder ranges in severity based on its species and the species of the host, the time of attack, and whether any viruses are also present in the host plant. By debilitating the host plant, dodder decreases the ability of plants to resist virus diseases, and dodder can also spread plant diseases from one host to another if it is attached to more than one plant.
A report published in Science (Vol 313; Sept. 29, 2006) by Runyon, Mescher, and De Moraes, researchers at Penn State University, demonstrates that dodder use airborne (volatile) chemical cues to locate their host plants. Seedlings of Cuscuta pentagona exhibit positive growth responses to volatiles released by tomato and other species of host plants. When given a choice between volatiles released by the preferred host tomato and the non-host wheat, the parasite exhibited preferential growth toward the former. Further experiments demonstrated attraction to a number of individual compounds released by host plants and repellance by one compound released by wheat. These results do not rule out the possibility that other cues (e.g., light) may also play a role in host location.
Prevention and treatment
Many nations have laws prohibiting import of dodder seed, requiring crop seeds to be free of dodder seed contamination. Before planting, all clothes should be inspected for dodder seed when moving from an infested area to a non-infested crop. When dealing with an infested area, swift action is necessary. Recommendations include planting a non-host crop for several years after the infestation, pulling up host crops immediately, particularly before the dodder produces seed, and use of preemergent herbicides like Dacthal in the spring. Examples of non-host crops include grasses and many other monocotyledons. If dodder is found before it chokes a host plant, it may be simply removed from the soil. If choking has begun, the host plant must be pruned significantly lower than the dodder, as dodder is versatile and can grow back if present from haustoria.
Vascular Plants of the Osa Peninsula, Costa Rica
sweetgum.nybg.org/osa/index.php
Los Charcos de Osa
CRTMRL
osa_00765
cross section: Acorus calamus
common name: Sweet Flag
magnification: 40x
Berkshire Community College Bioscience Image Library
The rhizomes, or horizontal stems, of Acorus are notable for their accumulation of aromatic medicinal oils.
The well cutinized epidermis is uniseriate showing radially elongated cells with thickened outer walls and occasional corky zones.
The cortex consists of an outer hypodermis of 3-5 layers of densely packed collenchyma cells. Beneath the hypodermis lies a wide zone of starch containing parenchyma cells with numerous intracellular spaces. These spherical cells form a tight network with vascular bundles and small fiber bundles positioned at the junctions of the network.
The boundary between the cortex and stele is marked by well-defined endodermis of one layer of thick walled barrel shaped starch contain cells. A casparian strip may be evident in some preparations.
As in the cortex, the parenchymatous cells of the stele are arranged in tight aerenchymatous chains. The vascular bundles within the stele are wrapped in bundle sheaths and form a nearly continuous ring just beneath the endodermis. Unlike those situated in the cortex, these bundles are rarely associated with fibers.
Both cortical and stelar vascular bundles are leptocentric, or amphivasal, meaning xylem and phloem are arranged in concentric rings with phloem to the inside and xylem to the outside of the bundle.
Scattered throughout the cortex and stele are clear or yellowish cells containing aromatic oils, dark brown staining tannins and polygonal crystals of calcium oxalate.
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Army Reserve medics help U.S. Army Africa make a difference
By Rick Scavetta, U.S. Army Africa
VICENZA, Italy – Army Reserve medical support for upcoming U.S. Army Africa missions was the main topic during Maj. Gen. Robert Kasulke’s recent visit to Caserma Ederle.
Kasulke, commander of the U.S. Army Reserve Medical Command, wrapped up a two-day visit to U.S. Army Africa headquarters on Mar. 17. During his stay, Kasulke met with senior U.S. Army Africa staff and toured garrison medical facilities – to include the final stages of construction of Vicenza military community’s new health clinic.
“The point of my visit is to work with U.S. Army Africa to get Army Reserve medical personnel more involved in missions in Africa,” Kasulke said. “We have a huge pool of fully-trained and certified medical folks that we can draw from. And there are great opportunities for medical missions on the African continent.”
Without assigned forces, U.S. Army Africa relies on support from other Army units to assign Soldiers for missions in Africa, said Col. Alfonso Alarcon, U.S. Army Africa’s senior medical officer. U.S. Army Africa needs to have a strong relationship with Army Reserve medical leaders to access Reserve medical staff for exercises, outreach clinics and familiarization events in Africa, Alarcon said.
“There are tremendous ways for Army Reserve medical Soldiers to make a difference and advance global security objectives through real-world training with our land forces partners in Africa,” Alarcon said.
Medical officers play a large role in U.S. Army Africa engagements, to include the 2009 exercise MEDFLAG in Swaziland. Another MEDFLAG exercise is being planned for central Africa this summer.
In October 2009, when a pregnant Ugandan woman arrived at a U.S. Army clinic during exercise Natural Fire 10, a U.S. Army Reserve officer – who happened to be a labor and delivery nurse in her civilian job in Abilene, Texas – helped the woman deliver her newborn son. Her efforts are one example of what Army Reserve medical staff can bring to military missions in Africa, Kasulke said.
For Army Reserve medics, taking care of patients overseas, in places that often lack quality healthcare, is a “soul-satisfying mission,” Kasulke said.
During the recent visit, Command Sgt. Maj. Roger Schulz, the Army Reserve’s senior medical noncommissioned officer, accompanied Kasulke, a vascular surgeon from upstate New York who took command of the Florida-based Army Reserve Medical Command in October 2009.
More than 28,000 Army Reserve Soldiers serve in medical roles. For several years, Reserve medics conducted training and exercises in place like Central America – experience that can be applied to U.S. Army Africa’s future missions, Kasulke said.
Some African medical officers are seeking help to develop better medical care, such as surgery centers and clinics. The Army Reserve has experts in establishing medical systems – from managers to professors – who could help organize assistance with that process, Kasulke said.
“The end point would be to help African partners develop systems that enable us to step back and they can carry on,” Kasulke said.
His command also has planners with experience organizing medical event that could help U.S. Army Africa staff, as the command continues to conduct military familiarization events on medical topics, where U.S. Army officers and NCOs discuss their profession with their counterparts.
Maj. Terry Clark, a U.S. Army Reserve officer, is on active-duty orders serving as a medical planner and physician assistant in the command’s surgeon office. Clark has recently led medical mentoring missions in Botswana, Malawi and Morocco.
“Working with African military medical officers offers a great opportunity for both U.S. Army Africa and the land forces of our African partner nations to build relationships that can lead to future events in the medical field,” Clark said. “We share information on how U.S. Soldiers conduct healthcare and also learn a lot about how medicine is practiced in Africa.”
PHOTOS by Sgt. 1st Class Kyle Davis, U.S. Army Africa
To learn more about U.S. Army Africa visit our official website at www.usaraf.army.mil
Official Twitter Feed: www.twitter.com/usarmyafrica
Official YouTube video channel: www.youtube.com/usarmyafrica
cross section: Medicago stem
common name: Alfalfa
magnification: 400x
Berkshire Community College Bioscience Image Library
Like most herbaceous dicots, Medicago is capable of limited amounts of secondary growth.
The uniseriate and cutinized epidermis contains trichomes and occasional stomata.
The narrow cortex consists of an outermost hypodermis of up to four or five layers of chlorenchyma with areas over stem ridges being strengthened with collenchyma.The middle cortical layer consists of a zone of loosely arranged parenchyma and the deepest layer, of a band of endodermis (starch sheath) that follows the contours of the underlying vascular bundles.
Within the stele the vascular bundles are arranged in a ring and separated from each other by wide medullary rays of parenchyma cells.
The collaterally arranged vascular bundles are almost entirely primary phloem and xylem. Each bundle consists of a large outer supportive cap of sclerenchyma fibers (phloem fiber cap), a deeper layer of primary phloem with well-defined sieve tubes and companion cells, and a deepest layer of primary xylem. In between the xylem and phloem, a narrow band of cambium may be seen. In some preparations, the highly lignified cells walls of xylem and mature sclerenchyma are stained red orange. These cells are dead at maturity and can also be distinguished by a heavy cell wall and absence of cytoplasm.
The center of the stem is occupied by a large pith of parenchyma cells that contain numerous starch storing amyloplasts.
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Vascular Plants of the Osa Peninsula, Costa Rica
sweetgum.nybg.org/osa/index.php
Los Charcos de Osa
CRTMRL
osa_01303
cross section: Tilia one year
magnification: 100x
Berkshire Community College Bioscience Image Library
Greater annual production of xylem results in a vascular cylinder dominated by well-defined annual rings of secondary xylem interspaced with narrow medullary rays of parenchyma cells. Each annual ring consists of large thin walled spring vessels that taper into progressively smaller, thick walled vessels and tracheids characteristic of later season wood.
The deepest zone of primary xylem is separated from the parenchymatous central pith by a starch sheath of dark staining starch filled parenchyma cells.
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cross section: Acorus root
common name: Sweet Flag
magnification: 400x
Berkshire Community College Bioscience Image Library
The cortex is well-developed and divided into two zones; an outer narrow layer of closely packed smaller parenchyma cells and a wide inner layer of open larger aerenchyma cells.
The inmost area of the cortex is bounded by an endodermis or starch sheath with larger barrel shaped cells and thickened walls that mark the casparian strip. Within the endodermis occasional small passage cells serve to transport water into the stele or vascular bundle.
The stele is bound in a pericycle of single layered thin walled parenchyma cells. A single central vascular bundle contains radiating arms of xylem and phloem. The xylem is exarch: meaning the earlier smaller protoxylem is found towards the periphery and younger larger metaxylem to the center of the stem.
Phloem tissues of seive tubes, companion cells and phloem parenchyma are also exarch. The older protophloem is found towards the periphery and metaphloem towards the center of the stem. Supportive sclerenchyma tissues and phloem caps are notably absent in most monocot stems. Vascular cambium is also absent, preventing secondary growth of the root.
The central region of the stele is occupied by thin walled starch containing aerenchyma cells.
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cross section: Pinus needle
magnification: 100x
Triarch quadruple stain
Berkshire Community College Bioscience Image Library
Deep to the hypodermis lies an undifferentiated photosynthetic mesophyll. Cells are distinctively lobed with infolded cell walls. They are filled with chloroplasts and starch grains that may be difficult to see because of an accumulation of dark staining tannins and resins. A few resin canals can be seen close to the hypodermal side of the mesophyll.
A central vascular bundle is wrapped in a single layered endodermis with a well-defined casparian strip whose end walls may become heavily suberized with age.
Deep to the endodermis lies a multilayered parenchymous pericycle with two vascular bundles separated by an often indistinct band of sclerenchymal cells. The pericycle also contains transfusion tissues of protein rich albuminous cells which abut and assist the phloem in the transport nutrients and elongated tracheidal cells which abut and assists the xylem in the transport of water.
Most species possess two conjoint, collateral vascular bundles, surrounded and supported by the tissues of the pericycle. Xylem tracheids lie towards the adaxial surface and phloem sieve tubes towards abaxial surface of the leaf. Xylem vessels and fibers, and phloem companion cells are absent in Gymnosperms.
While vascular bundles are closed some cambium may persist near the base of the needle.
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long section: Cucurbita stem
magnification: 400x
Berkshire Community College Bioscience Image Library
Bicollateral vascular bundles have two zones of phloem and two zones of cambium on either side of the central xylem with outer facing tissues more heavily developed.
The sequence of tissues in the bicollateral vascular bundle is outer phloem, outer cambium, xylem, inner cambium and inner phloem with outer more heavily developed.
Walls of xylem vessels have lignin free pits and lignin thickenings that form rings, spirals, networks and solid blocks.
Between the xylem and phloem are a few regularly arranged layers of elongated cambium cells.
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This image shows details of a vascular bundle from a young stem of a buttercup (Ranunculus sp.), a dicot. The red cells at the bottom of the image are xylem vessels. The smaller vessels in the centre are known as protoxylem, and are those first formed when the stem is elongating. The larger outer cells are called metaxylem. These cells mature later, when the stem has finished elongating. During their development, the cellulose walls of vessels become impregnated with lignin. Lignification supports the vessels and prevents them collapsing under tension. During the process of lignification the cells die and form continuous non-living tubes that transport water and mineral ions from the roots.
Above the xylem is a region stained green, which contains the phloem. Phloem consists of sieve tubes, which transport the products of photosynthesis from the leaves, along with their associated companion cells. Sieve tubes are living cells, but they lack nuclei. Each sieve tube has cytoplasmic connections to a smaller companion cell that provides the energy requirements of the sieve tube.
Between the xylem and phloem are some very small, undifferentiated cells called the cambium.
Cambium within a vascular bundle is called fascicular cambium. The parenchyma cells between vascular bundles can also develop into interfascicular cambium. This results in a complete ring of cambium around the periphery of the stem, which can divide mitotically and differentiate to produce more xylem and phloem, during the process called secondary thickening.
The diameter of the image is about 150 µm.
Image by John Adds
cross section: Richinus stem
magnification: 400x
Berkshire Community College Bioscience Image Library
Deep to the pericycle lies a ring of open vascular bundles interspaced with medullary rays of parenchymal cells. In older stems the isolated and open vascular bundles are replaced with continuous rings of phloem, cambium and xylem, interspaced with medullary rays.
Xylem is endarch with protoxylem found towards center of stem and younger metaxylem towards the periphery of the stem. Phloem is endarch but modest annual growth makes it difficult to distinguish between the older protophloem at the periphery and younger metapholem to the center of the stem.
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cross section: Zea root
common name: Corn
magnification: 400x
Berkshire Community College Bioscience Image Library
The inmost area of the cortex is bounded by an endodermis of elongated cells whose walls show a narrow band of suberization, marking the Casparian stip.
The outer stele is bound by a pericycle layer of thin walled parenchyma cells.
The vascular bundles are radially arranged with short arms of xylem interspaced with patches of phloem and parenchymous conjunctive tissue. The xylem is exarch: meaning the older smaller protoxylem is found towards the periphery and younger larger metaxylem to the center of the stem. Phloem tissues of sieve tubes, companion cells and phloem parenchyma are also exarch. The older protophloem is found towards the periphery and the younger metaphloem towards the center of the stem. Phloem parenchyma may become sclerenchymized in older roots. Vascular cambium is absent, preventing secondary growth of the root.
The central of the stele is occupied by large pith containing thin walled starch containing parenchyma cells.
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cross section: Zea stem
magnification: 400x
Berkshire Community College Bioscience Image Library
There is no apparent stele, rather the vascular bundles are scattered throughout the cortex with numerous small bundles crowded nearly the periphery of the stem and fewer larger bundles towards the center of the stem.
The vascular bundles are closed and collateral. Xylem is oriented towards the center of the stem and small amounts phloem to the outside. Cambium is lacking preventing secondary growth. In mature vascular bundles, the earliest protoxylem may break down to produce a large protoxylem cavity. The vascular bundles are wrapped in a bundle sheath of thick walled supportive sclerenchyma cells.
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Vascular Plants of the Osa Peninsula, Costa Rica
sweetgum.nybg.org/science/projects/osa/
www.facebook.com/loscharcosdeosa/
RA#17340 osa_03171
cross section: Younger Trifolium stem
common name: Clover
magnification: 400x
Berkshire Community College Bioscience Image Library
Like most herbaceous dicots, Trifolium dies at the end of the growing season and consequently capable of limited amounts of secondary growth
A band of endodermis (starch sheath) that follows the contours of the underlying vascular bundles.
Within the stele the vascular bundles are arranged in a ring and separated from each other by medullary rays of parenchyma cells.
The collaterally arranged vascular bundles are almost entirely primary phloem and xylem. Each bundle consists of a large outer supportive cap of sclerenchyma fibers (phloem fiber cap), a deeper layer of primary phloem with well-defined sieve tubes and companion cells, and a deepest layer of primary xylem. In between the xylem and phloem, a narrow band of cambium may be seen. In some preparations, the highly lignified cells walls of xylem and mature sclerenchyma are stained red orange. These cells are dead at maturity and can also be distinguished by a heavy cell wall and absence of cytoplasm.
The center of the stem is occupied by a large pith of parenchyma cells that contain numerous starch storing amyloplasts.
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cross section: Richinus stem
magnification: 400x
Berkshire Community College Bioscience Image Library
Deep to the pericycle lies a ring of vascular bundles interspaced with medullary rays of parenchymal cells. In older stems the isolated vascular bundles are replaced with continuous rings of phloem, cambium and xylem, interspaced with medullary rays.
Xylem is endarch with protoxylem found towards center of stem and younger metaxylem towards the periphery of the stem. Phloem is endarch but modest annual growth makes it difficult to distinguish between the older protophloem at the periphery and younger metapholem to the center of the stem.
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long section: Cucurbita stem
common name: Pumpkin/Squash
magnification: 100x
Berkshire Community College Bioscience Image Library
The vascular bundles are bicollateral; the central xylem is bound by an inner and outer cambium, and topped by a larger outer and a smaller inner phloem. Phloem consists of large clear sieve tubes with pitted cell walls and sieve plates, phloem parenchyma and small narrow green stained companion cells. Many sieve plates have deposits of a mucoid p-protein that forms as part of the trauma response in injured phloem. Xylem is well developed with numerous protoxylem evident towards the inside, and very large metaxylem to the outside of the bundles. Xylem consist primarily of large vessels and xylem parenchyma; tracheids and fibers are rare. Walls of xylem vessels have lignin free pits and lignin thickenings that form rings, spirals, networks and solid blocks. The vascular bundles are separated by zones of internal parenchyma.
The sequence of tissues in the bicollateral vascular bundle is large outer phloem, outer cambium, xylem, inner cambium and smaller inner phloem.
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cross section: Nymphaea stem
common name: Water Lily
magnification: 100x
Berkshire Community College Bioscience Image Library
The cells of the epidermis are single-layered, thin-walled and mucilaginous. There is no apparent cuticle.
The outer cortex consists of a narrow zone of 5 – 6 layers of parenchyma cells. The bulk of the cortex is occupied by network of thin walled aerenchyma cells. Chloroplasts may form throughout the cortex in stems exposed to sufficient light. The numerous air spaces of the aerenchymatous cortex store respiratory gases and provide bouncy. The only mechanical support within the cortex is provided by branched or stellate sclereids.
There is no well-defined stele, rather several smaller poly steles composed of two or more confluent vascular bundles loosely linked in a ring in the mid cortex. Single vascular bundles are distributed to the inside and outside of the zone of polysteles. All vascular bundles are closed and collateral with proto xylem in polysteles facing towards each other, followed by zones of metaxylem, and most externally, caps of phloem. A well-defined starch containing endodermis with casparian strip is evident in the poly stele systems.
Vascular tissues are often poorly differentiated into xylem and phloem. Xylem is entirely composed of spiral and annular tracheids of unusual length. In many vascular bundles a xylem lacuna can be seen. Phloem bundles are primarily phloem parenchyma and sieve tubes.
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cross section: Pinus stem
magnification: 400x
Triarch quadruple stain
Berkshire Community College Bioscience Image Library
The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem.
Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells.
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cross section: Sparganium stem
common name: burr reed
magnification: 400x
Berkshire Community College Bioscience Image Library
The vascular bundles in the roots and stems of monocots are typically closed, meaning the xylem and phloem are adjacent to each other. There is no vascular cambium, limiting the possibility of secondary growth. The vascular tissues are often wrapped in a bundle sheath of starch containing parenchyma or supportive, heavy walled sclerenchyma.
The vascular bundles in the stem of the monocot Sparganium are both closed and collateral, meaning xylem and phloem are adjacent to each other and occupy the same radii on the stem axis.
Within each vascular bundle proto and metaxylem are arranged in a V shape with phloem situated in between and above the metaxylem.. A protoxylem lacunae is usually formed. The closed vascular bundles are wrapped in a bundle sheath of thick walled sclerenchyma cells. Vascular cambium is absent preventing the formation of secondary tissues.
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cross section; Zea stem
magnification: 100x
Berkshire Community College Bioscience Image Library
A single layered, cutinized epidermis overlies an interior composed entirely of cortical tissues. Within the cortex a few layers of sclerenchyma can be seen just beneath the epidermis. Below that lies a cortical region composed entirely of loosely packed thin walled parenchyma and intercellular spaces.
There is no apparent stele, rather the vascular bundles are scattered throughout the cortex with numerous small bundles crowded nearly the periphery of the stem and fewer larger bundles towards the center of the stem.
The vascular bundles are closed and collateral. Xylem is oriented towards the center of the stem and small amounts phloem to the outside. Cambium is lacking preventing secondary growth. In mature vascular bundles, the earliest protoxylem may break down to produce a large protoxylem cavity. The vascular bundles are wrapped in a bundle sheath of thick walled supportive sclerenchyma cells.
Unlike most grasses Zea stems are not hollow at the center.
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cross section: Zea stem
magnification: 40x
Berkshire Community College Bioscience Image Library
A single layered, cutinized epidermis overlies an interior composed entirely of cortical tissues. Within the cortex a few layers of sclerenchyma can be seen just beneath the epidermis. Below that lies a cortical region composed entirely of loosely packed thin walled parenchyma and intercellular spaces.
There is no apparent stele, rather the vascular bundles are scattered throughout the cortex with numerous small bundles crowded nearly the periphery of the stem and fewer larger bundles towards the center of the stem.
The vascular bundles are closed and collateral. Xylem is oriented towards the center of the stem and small amounts phloem to the outside. Cambium is lacking preventing secondary growth. In mature vascular bundles, the earliest protoxylem may break down to produce a large protoxylem cavity. The vascular bundles are wrapped in a bundle sheath of thick walled supportive sclerenchyma cells.
Unlike most grasses Zea stems are not hollow at the center.
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cross section: Acorus calamus
common name: Sweet Flag
magnification: 400x
Berkshire Community College Bioscience Image Library
The rhizomes, or horizontal stems, of Acorus are notable for their accumulation of aromatic medicinal oils.
The well cutinized epidermis is uniseriate showing radially elongated cells with thickened outer walls and occasional corky zones.
The cortex consists of an outer hypodermis of 3-5 layers of densely packed collenchyma cells. Beneath the hypodermis lies a wide zone of starch containing parenchyma cells with numerous intracellular spaces. These spherical cells form a tight network with vascular bundles and small fiber bundles positioned at the junctions of the network.
The boundary between the cortex and stele is marked by well-defined endodermis of one layer of thick walled barrel shaped starch contain cells. A casparian strip may be evident in some preparations.
As in the cortex, the parenchymatous cells of the stele are arranged in tight aerenchymatous chains. The vascular bundles within the stele are wrapped in bundle sheaths and form a nearly continuous ring just beneath the endodermis. Unlike those situated in the cortex, these bundles are rarely associated with fibers.
Both cortical and stelar vascular bundles are leptocentric, or amphivasal, meaning xylem and phloem are arranged in concentric rings with phloem to the inside and xylem to the outside of the bundle.
Scattered throughout the cortex and stele are clear or yellowish cells containing aromatic oils, dark brown staining tannins and polygonal crystals of calcium oxalate.
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The thromboembolus consists of fibrin and platelets (center) with adherent clotted blood. Compare with appearance of a blood clot.
Vascular Plants of the Osa Peninsula, Costa Rica
sweetgum.nybg.org/osa/index.php
Los Charcos de Osa
RA#15682 osa_00079
The transparency of zebrafish larvae makes it possible to use high-resolution imaging to visualize in detail the entire vasculature, or system of blood vessels. Credit: NICHD
cross section: Acorus calamus
common name: Sweet Flag
magnification: 100x
Berkshire Community College Bioscience Image Library
The rhizomes, or horizontal stems, of Acorus are notable for their accumulation of aromatic medicinal oils.
The well cutinized epidermis is uniseriate showing radially elongated cells with thickened outer walls and occasional corky zones.
The cortex consists of an outer hypodermis of 3-5 layers of densely packed collenchyma cells. Beneath the hypodermis lies a wide zone of starch containing parenchyma cells with numerous intracellular spaces. These spherical cells form a tight network with vascular bundles and small fiber bundles positioned at the junctions of the network.
The boundary between the cortex and stele is marked by well-defined endodermis of one layer of thick walled barrel shaped starch contain cells. A casparian strip may be evident in some preparations.
As in the cortex, the parenchymatous cells of the stele are arranged in tight aerenchymatous chains. The vascular bundles within the stele are wrapped in bundle sheaths and form a nearly continuous ring just beneath the endodermis. Unlike those situated in the cortex, these bundles are rarely associated with fibers.
Both cortical and stelar vascular bundles are leptocentric, or amphivasal, meaning xylem and phloem are arranged in concentric rings with phloem to the inside and xylem to the outside of the bundle.
Scattered throughout the cortex and stele are clear or yellowish cells containing aromatic oils, dark brown staining tannins and polygonal crystals of calcium oxalate.
Technical Questions:bioimagesoer@gmail.com
cross section: Acorus calamus
common name: Sweet Flag
magnification: 400x
Berkshire Community College Bioscience Image Library
The rhizomes, or horizontal stems, of Acorus are notable for their accumulation of aromatic medicinal oils.
The well cutinized epidermis is uniseriate showing radially elongated cells with thickened outer walls and occasional corky zones.
The cortex consists of an outer hypodermis of 3-5 layers of densely packed collenchyma cells. Beneath the hypodermis lies a wide zone of starch containing parenchyma cells with numerous intracellular spaces. These spherical cells form a tight network with vascular bundles and small fiber bundles positioned at the junctions of the network.
The boundary between the cortex and stele is marked by well-defined endodermis of one layer of thick walled barrel shaped starch contain cells. A casparian strip may be evident in some preparations.
As in the cortex, the parenchymatous cells of the stele are arranged in tight aerenchymatous chains. The vascular bundles within the stele are wrapped in bundle sheaths and form a nearly continuous ring just beneath the endodermis. Unlike those situated in the cortex, these bundles are rarely associated with fibers.
Both cortical and stelar vascular bundles are leptocentric, or amphivasal, meaning xylem and phloem are arranged in concentric rings with phloem to the inside and xylem to the outside of the bundle.
Scattered throughout the cortex and stele are clear or yellowish cells containing aromatic oils, dark brown staining tannins and polygonal crystals of calcium oxalate.
Technical Questions:bioimagesoer@gmail.com