Biology Microscopy - Plant Anatomy

Coleus stem xs. x40. The pointer shows a vascular bundle. Numerous parenchyma cells are in the center. A small thickness of secondary tissue consisting of straight rows of cells exists between and within the vascular bundles.
Collenchyma cells with thickened corners of their primary cell walls are located just inside of the epidermis in this Helianthus stem. x400.
Parenchyma cells are located in the central pith and the cortex of this Helianthus stem. x100. Each vascular bundle has a dense layer of fibers, then green staining phloem, then red staining xylem with large vessels as you move from the outside toward the inside of the vascular bundle.
Helianthus stem xs. x40. Note the ring of vascular bundles in this typical dicot stem.
Sieve tube and sieve plate, ls. Two sieve tube elements are separated by a porous sieve plate. The red substance is callose, a carbohydrate plants use to plug their sieve pores when phloem is injured. Cucumber stem x400.
Tracheids with scalariform pits. Lycopodium cone ls. x1000.
Tracheids with spiral pits. Lycopodium cone ls. x1000.
Sieve pores in the end walls of sieve tube elements. The sieve pores appear as black dots. Moonseed vine xs. x1000.
Phloem region within a vascular bundle. From right to left (from the outside toward the center of the stem) you can see red staining thick walled fibers, then sieve tube elements some with sieve plates and their sieve pores, and then the vascular cambium. Moonseed vine xs. x400.
Moonseed vine vascular bundle. The large diameter cells are vessels within the xylem.
Circular bordered pits in a tracheid. Pinus macerated wood. x400.
Simple pits in a tracheid. Pinus macerated wood. x400.
Circular boardered pits seen from the side. The "boarder" is actually secondary cell that has separated from the primary cell wall. The dark structures are thick areas of primary cell wall inside the pit apeture, or hole, within the secondary cell wall. Pinus wood. rs. x1000.
Large diameter vessel element. The diameter is almost as great as the (short) length of the cell. Note the perforated ends and the pits on the lateral wall. Quercus macerated wood. x100.
Another vessel element with perforated end walls. Quercus macerated wood. x100.
Central part of a fiber. Note the relatively thick cell wall and the presence of only a few pits. Quercus macerated wood. x400.
Pointed end of a fiber. Note the tiny cell lumen in the center surrounded by thick cell walls. Quercus macerated wood. x400.
Tilia vessel elements. Tilia macerated wood. x100.
Another fiber pointed end. Tilia macerated wood. x400.
A stack of vessel elements forming a vessel in wood. Tilia wood rs. x100.
A single Helianthus vascular bundle. x100. Note collenchyma cells near the outside of the stem and parenchyma cells near the center. The vascular bundle shows from the outside in fibers, phloem, vascular cambium, and xylem. The large red staining cells within the xylem are vessel elements.
Vessel in a corn stem. The vessel consists of several stacked vessel elements. To the right of the vessel are green staining phloem cells and red staining fibers, all of which form part of a vascular bundle seen here in longitudinal section. Zea mays stem ls. x100.
Annular (ring) pits in a vessel element. Zea mays stem ls. x400.
Simple and scalariform pits in a vessel element. Zea mays stem ls. x400.
Circular bordered pits. Pinus wood rs. x1000.

Corn root ls x40. Note the larger more rectangular cells in the region of elongation beyond the root cap and apical meristem.
Onion root tip ls x100. You can see the root cap and a portion of the apical meristem. The outer part of the root cap is shown sloughing off which it does to protect the apical meristem as the root burrows its way through the soil.
Fern root tip x40. Non seed plants such as ferns often have shoot and root apical meristems with a single large central apical cell.
Young dicot root x40 with three xylem lobes in the central vascular cylinder. The purple structures are starch-storing leucoplasts in parenchyma cells of the root cortex.
Young dicot root vascular cylinder x100. The arrow indicates a non-lignified "passage cell" in the endodermis. Such cells lack secondary cell walls and permit the passage of water and minerals between the xylem and cortex. Nearby endodermal cells that are lignified do not permit such passage.
Protoxylem and phloem in a young dicot root x400. You can see staining red two of the three protoxyem lobes of this root. Primary phloem (arrow) and vascular cambia are visible. The metaxylem cells in the center have not yet developed secondary cell walls and thus stain green. Later in the development of this root, the metaxylem cells will form a secondary cell wall.
Ranunculus(Buttercup) root xs x40. There are four xylem lobes in this "typical dicot root" similar to roots illustrated in most biology textbooks. Purple staining structures are starch containing leucoplasts in cells of the cortex.
Ranunculusroot vascular cylinder x400. In this specimen, the metaxylem (central last maturing xylem) has fully formed lignified secondary cell walls. From the top center down, you can see the cortex,endodermis, pericycle, phloem, vascular cambium, and xylem.
Psaroniusroot xs x40. This is a 300 million year old petrified fern root that looks very much like modern dicot roots. You can see from the outside toward the center indications of a cortex,endodermis, phloem, and 5 lobed xylem.
Orchid root xs x100. A two layered cortex surrounds the central vascular cylinder. The arrow indicates a passage cell in the endodermis immediately outside of a group of xylem cells.
Orchid root vascular cylinder x400. The arrow indicates a passage cell in the otherwise lignified endodermis. Cells with thin red staining walls inside the passage cells are xylem. Cells with thick red staining walls are fibers. There are small green staining patches of phloem with each group of fibers, alternating in position with xylem groups.
Monocot root xs x40. You can see a pith surrounded by a vascular cylinder, cortex, and a root hair-bearing epidermis. A branch root originates at the outer part of the vascular cylinder. The large white circular areas are tube-shaped holes in the root that function like vessels in water conduction.
Monocot root vascular tissue x400. Moving from the top down, you can see the cortex, endodermis, 3 groups of red staining protoxylem with phloem in between each group, and pith. The hole in the outer pith is tube-shaped and functions like a vessel in water conduction.
Salix(Willow) branch root x40, pushing through the cortex of its parent root.
Salixbranch root origin x100. You can see the "X"shaped xylem of the parent root in cross section and a longitudinal section of the branch root on the right. The branch root originates at the pericycle of the parent root, just outside the parent root's primary xylem.
Tulip tree woody root xs x12. This woody root with secondary xylem and phloem looks very much like a woody stem. The branch root on the left originating near the center of the parent identifies this photograph as a woody root rather than a woody stem.
Tulip tree root secondary tissues xs x40. From the bottom to the top, you can see secondary xylem with vessels and rays,the vascular cambium, secondary phloem, and cortex.
Zeamays root hair x400. Root hairs are extensions of epidermal cells as seen in this root ls.
Clover root nodule x40. Nodules like this in legume plantroots are about the size of small peas. They contain symbiotic nitrogen fixing bacteria in their center cells. The bacteria, with the help of hemoglobin (yup, the same stuff found in animal blood) apparently made by the plant, convert atmospheric N2 gas into nitrate and nitrite ions that the plant can use.

Alternate leaf arrangement. #17 Eastern Redbud.
Pinnately compound leaf. #3 White Ash.
Palmately compound leaf. #7 Ohio Buckeye.
Palmate venation. #4 Sycamore.
Abscission zone. Longitudinal section of Acer stem x40 with leaf petiole coming off to the left. Arrow shows the abscission zone. A vein enters the leaf passing through the abscission zone.
Asclepias leaf abscission x40. The pointer shows the abscission zone in this stem ls. The petiole is on the left with a vein passing through the abscission zone. A group of flower buds is on the right.
Asclepias leaf abscission x100. Note the cork cells on both the petiole surface and extending across the abscission zone.
Acer sun leaf xs. x400. Note the dense palisade mesophyll in this leaf that was exposed to direct sunlight. Spongy mesophyll is in the lower half of the leaf.
Acer shade leaf xs. x400. The palisade mesophyll is less dense and the spongy mesophyll is more extensive in this shaded leaf compared to leaves on the same tree that were exposed to direct sun.
Stoma and guard cells xs. on Acer lower epidermis. x1000. Two guard cells have a small opening (stoma) between them for gas exchange. Note the large intercellular space, part of the spongy mesophyll, immediately inside the stoma.
Monocot leaf bases x20 frequently form sheaths around the stem that bears them. Such leaves have no petioles and are broadly attached to the stem at the base of the leaf.
Ammophila leaf xs.. x40. This is a beach grass leaf that is curled in the adaxial (upper surface) direction due to temporary drought conditions. Unlike most leaves, most stomata are on the upper surface where they are protected from rapid water loss by the high relative humidity within the curled leaf. White buliform cells can be seen at the base of the V-shaped notches on the adaxial (inner, upper) leaf surface. The leaf uncurls when these buliform cells fill with water, enlarge, and become turgid when drought conditions end.
Buliform cells x400. The large buliform cells are on the right at the base of a V-shaped notch on the upper epidermis of a curled beach grass (Ammophila) leaf. Stomata in xs can also be seen associated with intercellular spaces within the leaf mesophyll. When the buliform cells fill with water and enlarge this causes the leaf to uncurl.
Clivia leaf xs. x40. This is a monocot leaf. Note the mesophyll which is not easily distinguishable as palisade vs spongy. The cuticle is somewhat thicker on the upper surface.
Clivia leaf vein xs. x100. The large red ringed cells are vessels, part of the xylem. The small cells below are phloem. In leaves the xylem of veins is always toward the adaxial (upper) surface and the phloem toward the abaxial (lower) surface. In monocot leaves such as Clivia xylem-phloem placement within a vein is the only way to identify the upper and lower surface of a leaf seen in cross section.
Stoma, guard cells, and cuticle xs. x400. The red material is cuticle covering the lower epidermis of a Clivia leaf. You can see a pair of guard cells, a stoma between them, and cuticular hairs partically covering the stoma. The covering of cuticular hairs helps maintain high relative humidity near the stomatal opening and reduce rapid water loss through the stoma.
Monocot leaf epidermis x40. You can see pairs of guard cells and other cells of this upper epidermis. Dark dots are nuclei. Rectangular cells are over a leaf vein. Stomata are between veins.
Tradescantia upper leaf epidermis x100. Note the lack of stomata on this leaf surface. The black dots are nuclei. Unlike this species, many dicot plants have a few stomata on their upper surface. Most of a dicot leaf's stomata are usually found on the lower surface.
Tradescantia lower leaf epidermis x100. There are lots of pairs of guard cells, each surrounding a stoma.
Stoma, surface view x400. This shows a single pair of guard cells surrounding a stoma on the lower epidermis of Tradescantia. The large dark bodies are nuclei. The lighter circular bodies within the guard cells are chloroplasts. In most plants guard cells are the only cells within a leaf's epidermis that contain chloroplasts. The production of sugar by photosynthesis in the daytime within guard cells and not in adjacent epidermal cells causes water to diffuse into the guard cells. This makes the guard cells swell, opening the stoma.
Ligustrum leaf xs. x40. A typical dicot leaf. Note the large central vein as well as the palisade and spongy mesophyll.
Mid vein of a Ligustrum leaf. x100.
Ligustrum leaf mesophyll and small veins x100. Note that one of the small veins is in good cross section and another is very oblique. This shows that the three visible veins are not parallel to each other and thus that the leaf does not have parallel venation. This means that the leaf must have net venation and thus must be a dicot leaf.
Net venation in paradermal view x100. This Ligustrum leaf is sectioned parallel to the leaf surface through the spongy mesophyll. You can see the net-like arrangement of the smallest veins which is the basis for the name "net venation".
Zea mays leaf xs x100. This corn leaf is typical of monocot leaves with their characteristic parallel venation. You can tell that the venation is parallel because the veins are all shown in nice cross section. The only way to identify the true upper surface of the leaf is to look for the xylem in the veins, which is always positioned toward the upper epidermis. There are stomata visible in both the upper and lower epidermis. Some large buliform cells are on the right side of the upper epidermis. Shrinkage of these buliform cells would cause the leaf to curl upward.
Zea mays leaf vein x400. At the top and bottom of the vein are groups of fibers. The secondary cell walls of the xylem cells stain red, including the two very large diameter vessels. Small sieve tubes and companion cells in the phloem stain dark green.
Zea mays buliform cells in the upper epidermis of a leaf x400. The tiny cells in the two small veins are phloem.
Pinus leaf xs x100. One of a group of two leaves near the leaf base. The outer mesophyll is very dense and contains a resin duct visible on the right. One of several visible stomata can be seen on the right side of the bottom surface.

Overwintering terminal bud of sugar maple x8. A nearby lateral branch bud is also visible. Terminal bud scales are easily seen. These scales fall off as the stem elongates leaving behind a set of terminal bud scale scars.
Terminal bud scale scars on sugar maple x15. A set of scars such as these completely surround the stem, unlike leaf scars. They are found along the stem where one growth year ends and the next begins. The most recent year's growth shown here is to the right.
Lenticels on the surface of a twig x15. These allow gas exchange through the water and gas proof cork layer that covers small twigs.
Leaf scar x10. The "smiley face" is a curved row of vein scars where the veins once entered the leaf through the abscission zone. A dormant lateral branch bud is immediately above the leaf scar on the left side of the photograph.
Elodeaapical meristem x40 showing lots of leaf primordia.
Coleusapical meristem x40. Note the immature vascular bundles in the stem extending as veins into leaves.
Coleusapical meristem close up x100. Note the leaf primordia. Also note the two lateral branch bud meristems immediately above the large leaves.
Helianthusyoung stem xs x40. A typical dicot stem with a ring of vascular bundles. Everything you see here is primary tissue because the vascular cambium has not yet become active.
Lilliumstem xs x40. A typical monocot stem with scattered vascular bundles.
Zeamays stem xs x40. Another typical monocot stem with scattered vascular bundles.
Corn vascular bundles scattered within the parenchyma ground tissue ofthe stem x100. The phloem of each bundle is toward the top in this photograph. The two large cells within each bundle are vessels. The white area in the bottom center of each bundle is a large intercellular space that functions as a vessel. This tube-shaped intercellular space was formed during the bundle's growth when some cells of the bundle continued to elongate while some nearby xylem cells could not elongate because they had become lignified. The result was a tearing apart of the lignified cells.
A single Helianthus vascular bundle from a ring of vascular bundles in a dicot stem x100. Note collenchyma cells near the outside of the stem and parenchyma cells near the center. The vascular bundle shows from the outside in fibers, primary phloem, vascular cambium, and primary xylem. The large red staining cells within the xylem are vessel elements. The vascular cambium of this bundle is just starting to become active and has produced a few radially aligned rows of cells.Eventually the primary xylem and phloem of this bundle will be pushed apart by the production of secondary xylem and phloem by the vascular cambium.
Young Coleus stem xs x40. Some parenchyma cells between vascular bundles have become meristematic linking the vascular cambium of the large vascular bundle (arrow) with adjacent smaller vascular bundles. The result is a complete ring of radially aligned cells circling the stem and separating the pith from the cortex. These radially aligned cells will become secondary xylem and phloem.
Wood block illustrating cross section (xs), radial section (rs), and tangential section (ts) cuts.
A log split radially (radial section) illustrating heartwood,sapwood, pith, and a lateral branch buried in the secondary xylem ofthe log.
Pawpaw stem xs x100 with a growth ring. The large cells are vessels. The small diameter cells are mainly fibers. In which direction is the outside of the stem, to the right or to the left?
Monocot stem xs with secondary vascular bundles x40. This is a palm-likeplant (Beaucarnia) in the family Agavaceae. The entire (butmainly the outer) cortex remains meristematic and produces secondary vascular bundles, resulting in an increase in stem diameter. Inmonocots, there is no single vascular cambium, like that found in virtually all other plant groups with secondary growth.
Monocot secondary vascular bundles x100. These Beaucarniasecondary vascular bundles have a small patch of phloem in the center that is completely surrounded by xylem.
Pinusone year old stem xs x100. You can see secondary xylem, vascular cambium, secondary phloem, cortex, and a cork cambium. The cells immediately outside the cork cambium have been cut off from water and are dead, appearing here to be clear with no cytoplasm. There are two resin ducts, each surrounded by small secretory cells, within the cortex.
Pinuswood xs x100. A growth ring and resin duct are visible in this cross section. Most of the cells are tracheids. In which direction is the outside of the stem, towards the top or bottom of the illustration?
Pinuswood ts x100. Short rays one cell in width are seen in this tangential section.
Cork layers xs x40 on the outer surface of an oak (Quercus)stem. Several cork cambia are visible. The upper part of the illustration shows the outer secondary phloem where new cork cambia and cork layers will soon form.
Tyloses in an oak vessel rs x100. A large vessel filled with tyloses(plugs) in the heartwood of an oak tree. A smaller functioning (notyloses) vessel composed of several vessel elements is on the left.
Oak vascular cambium and phloem rs x400. The vascular cambium is within the narrow white cells center-right. Phloem with blue staining sieve areas is center-left.
Oak wood ts x100. A very tall wide ray and numerous small rays are visible in tangential section. The blue cells are all fibers.
Oak vascular cambium xs x400. The blue cells are secondary xylem and the larger white cells are secondary phloem. The vascular cambium extends from right to left within the small rectangular cells. Note that rays extend from xylem through the cambium and into the phloem.
Oak xylem and phloem xs x40. A lower magnification view of the previous illustration. The solid blue area of cells are fibers and vessels of the secondary xylem. Immediately outside of the blue staining xylem is the vascular cambium. The secondary phloem has blue staining fibers within it. Note that the older (outer) secondary phloem is becoming crushed. Only the most recently formed phloem near the vascular cambium actually functions as phloem.
Tiliayoung stem xs x100. From the bottom to the top, you can see epidermis (sloughing off), cork, cortex, fibers that used to be on the outer part of a vascular bundle, primary phloem, secondary phloem with rows of fibers, vascular cambium, and secondary xylem. The old vascular bundles are still partially separated in the area of the phloem by pithrays made of parenchyma cells.
Tiliacork cambia and phloem xs x100. The wedge shaped structures are primary and secondary phloem. Secondary xylem is just visible at the top of the photograph. At least two and probably several more cork cambia can be seen at successively deeper layers within the phloem.
Tiliawood xs x400. A ray runs vertically and a growth ring can be seen horizontally. In which direction is the outside of the stem, toward the top or bottom of the photograph? The large cells are vessels. Small diameter cells are mostly small vessels, fibers, and wood parenchyma.
Tiliawood tangential section x40. Two very tall rays each 2 cells wide are visible on the right and left sides of the photograph. The other cells are vessels, thin walled fibers, and wood parenchyma (small rectangular vertically aligned cells).

Academics

Biology Microscopy - Plant Anatomy

Plant Tissues and Cell types

Roots

Leaves and Leaf Anatomy

Stems