Plant Anatomy - 2013

Section 3. CONTENT MODULE 2. PLANT TISSUES

I. Research objects: onion ROOT tips, pumpkin stems and roots, elderberry branches.

Equipment and supplies: microscopes, magnifying glasses, Glass slides and cover slips, razor blades, dissecting needles, tweezers, dropper bottles, distilled Water, Sudan III solution, permanent Microscope slides, charts: "Root Apical Meristem"; "SHOOT Apical Meristem"; "Periderm"; "Pumpkin Stem"; "Branch Section".

Task 1.

Prepare a microscope slide of a root tip and study the MICROSTRUCTURE OF THE apical meristem.

Place a 1 cm-long onion root tip onto a glass slide in a drop of water, cover with a coverslip, and examine it under low magnification. Locate the root cap, the division zone just above it, and further up, The Cell elongation zone. Together, these make up the growth zone. Positioned above the growth zone is the absorption zone, where permanent Tissues begin to form. Above this lies the largest zone — the conduction (or strengthening) zone, where all tissues are already permanent. Under low magnification, examine the growth zone to identify its three meristematic layers (histogens): the outer grey layer (dermatogen), beneath it the broad light-coloured layer (periblem), and the inner dark central core (plerome). Note that in the absorption zone, the dermatogen gives rise to the epiblema — the primary dermal tissue with root hairs; the periblem develops into the primary cortex; and the plerome forms the central vascular cylinder of the root.

Draw the onion root tip, showing all zones populated with the corresponding Cells. Label the longitudinal features on the diagram: root cap, division zone, elongation zone, absorption zone, and the onset of the conduction zone above it. In the transverse view within the elongation zone, label the three histogens: dermatogen, periblem, and plerome; and in the absorption zone, label the tissues derived from them: epiblema, primary cortex, and central vascular cylinder. Draw Conclusions based on your findings.

Task 2.

Prepare a cross-section microscope slide of a stem and study the microstructure of secondary lateral Meristems: phellogen and cambium.

Prepare cross-sections of an elderberry branch and a pumpkin stem, place them on glass slides, and apply a drop of Sudan III to the elderberry section and water to the pumpkin section. Cover with coverslips, clear the sections, and examine the cortical region of the elderberry branch under low magnification. Pay attention to the tightly packed radial rows of cork cells, which stain orange with Sudan III. Beneath the cork cells lies a single layer of cells dividing by tangential walls. This is the cork cambium, or phellogen. Note that towards the inside, the phellogen produces oval phelloderm cells containing green METABOLISM/14.html">Chloroplasts. Far fewer phelloderm cells are produced compared to cork — only 2-3 layers.

Draw several phellogen cells with rectangular cork cells formed on the outside and oval phelloderm cells on the inside. Label and annotate the drawing.

Next, examine the cross-section of the pumpkin stem to locate the vascular bundle and, within it, the cambium. Note that the cambium produces small phloem cells outwardly and relatively large xylem cells inwardly. The first rows of phloem and xylem resemble cambial cells in shape, which is why this region is referred to as the cambial zone. However, keep in mind that the cambium is always strictly a single layer of cells that continuously divide tangentially, adding phloem to the outside and xylem to the inside.

Draw several cambial cells along with the produced phloem and xylem cells. When making your drawings, follow the rule that each cambial (and phellogen) cell produces only one cell outwardly and one inwardly. This process is continuous, so the generated cells are arranged in neat radial rows, which is especially distinct in the xylem.

II. Research objects: iris leaves, elderberry leaves, elderberry branches, oak bark.

Equipment and supplies: microscopes, magnifying glasses, glass slides and cover slips, razor blades, dissecting needles, tweezers, dropper bottles, distilled water, chloral hydrate solution, Sudan III solution, filter paper, charts: "Epidermis of Monocots and Dicots", "Types of Stomatal Complexes", "Types of Cuticle", "Periderm with Lenticel", "Oak Rhytidome", permanent

microscope slides.

Task 1.

Prepare a surface microscope slide of a monocot leaf epidermis and study its microstructure.

Using a razor blade and needle, peel the epidermis from an iris leaf and prepare a slide in a drop of chloral hydrate solution. Clear the preparation and examine it under low and then high magnification of the microscope. Note the prosenchymatous cell shape, straight and tightly fitting cell walls, orderly arrangement of Stomata, and the presence of chloroplasts exclusively within the guard Cells of the stomata.

Draw a fragment of the epidermis showing stomata, accessory (subsidiary) cells, and ordinary epidermal cells. In the stomata, label the guard cells containing chloroplasts and the stomatal pore. Annotate the drawing. Draw appropriate conclusions.

Task 2.

Prepare a cross-section microscope slide of a leaf and study the microstructure of epidermal cells.

Prepare several cross-sections of an iris leaf, select the thinnest one, and transfer it to a glass slide in a drop of Sudan III solution. Cover with a coverslip and examine under low and high magnification of the microscope. Note that in cross-section, the epidermal cells are parenchymatous in shape. The outer Cell wall of the epidermis is thicker than the inner wall and is covered with a cuticle, which stains

pink with Sudan III solution. Locate the guard cells of the stomata and the substomatal air chamber beneath them.

Draw several epidermal cells with the cuticle, a stomatal apparatus with the substomatal air chamber beneath it, and a single layer of cells beneath the epidermis. Label the drawing with: the cuticle, guard cells, subsidiary and proper epidermal cells, and the air chamber. Add a title to the drawing and draw conclusions from the work performed.

Task 3.

Prepare a surface micropreparation of a dicotyledonous leaf epidermis and study its microstructure.

Using a razor blade or needle, peel off the epidermis from the lower side of an elderberry leaf and prepare a micropreparation in a drop of chloral hydrate. Examine under low and high magnification of the microscope. Pay attention to the irregular shape and wavy cell walls, the random distribution of stomata, and simple air hairs. Count the number of cells adjacent to the stoma and identify the stomatal complex.

Sketch a fragment of the epidermis showing several stomata, subsidiary and proper epidermal cells, and a simple air Hair. Label and caption the drawing. Draw conclusions from the research carried out.

Task 4.

Prepare a micropreparation of a woody plant stem cross-section and study The Structure of the periderm.

Make several cross-sections of an elderberry twig. Select the thinnest one and transfer it to a microscope slide in a drop of Sudan III solution. Cover with a coverslip and clear. Examine under low and high magnification of the microscope. Locate the periderm, lenticel, and remnants of the shedding epidermis. Note the radially arranged rows of rectangular cork cells, which have stained orange with the Sudan III solution. Beneath the cork, locate a row of flat phellogen cells divided tangentially into two halves. Beneath the phellogen, find several rows of oval phelloderm cells containing green chloroplasts.

Sketch a periderm fragment from the cross-section and label its constituent parts. Caption the drawing. Draw conclusions from the studies performed.

Task 5.

Prepare a micropreparation of a tree bark cross-section and study the microstructure of the rhytidome.

Using a razor blade, make several cross-sections of oak bark, select the thinnest one, and transfer it to a microscope slide in a drop of Sudan III solution; cover with a coverslip and clear. Under low microscope magnification, locate the cork bands that have turned orange from the Sudan III solution. Moving the micropreparation, count the number of cork bands in the rhytidome and deduce the number of periderms it contains. Note that the cork bands alternate with dark layers of dead bark tissues.

Sketch a diagram of the rhytidome. Label the cork layers and the areas of dead tissue between them on the diagram. In the innermost periderm (adjacent to the bark

of the trunk), depict the living phelloderm (with green chloroplasts). Caption the drawing. Draw a Conclusion from the study conducted.

III. Objects of Study: motherwort stem, elderberry twig, linden petioles, oak bark, sunflower stem, pumpkin stem, corn stem.

Materials and equipment: microscopes, magnifying glasses, glass slides and coverslips, razor blades, dissecting needles, tweezers, dropping bottles, distilled water, chloral hydrate solution, chlor-zinc-iodine solution, phloroglucinol, concentrated acids - HCl and H₂SO₄, permanent micropreparations, charts: "Mechanical Tissues"; Conducting tissues - vessels and tracheids; "Conducting tissues - sieve tubes and companion cells".

Task 1.

Prepare a micropreparation of a stem cross-section and study the Structural Features of collenchyma.

Make a cross-section of a motherwort stem or elderberry twig, place it in a drop of chloral hydrate, cover with a coverslip, and clear. Examine under low microscope magnification and find the collenchyma in the stem ridges (or beneath the periderm in the elderberry twig). Pay attention to the angular thickenings of the cell walls in motherwort (or tangential thickenings in elderberry), which makes the collenchyma resemble a checkerboard pattern. Draw off the chloral hydrate with filter paper and apply a solution of chlor-zinc-iodine to the dried section. The blue coloration of the collenchyma indicates the cellulosic Nature of the cell wall thickenings and the living cell contents.

Sketch a fragment of angular or lamellar collenchyma under high microscope magnification. Label and caption the drawings. Draw appropriate conclusions regarding the microscopic examination of the sections.

Task 2.

Prepare a micropreparation of cross and longitudinal stem sections and study the structure of bast fibers.

The Study of fibers on a cross-section can be carried out using the previous micropreparation. To do this, examine the preparation just below the collenchyma (towards the center of the organ) and locate groups of oval cells that appear silvery under the microscope and have a tiny black lumen in the center (the cell contents have died off). To study fibers on a longitudinal section, it is best to use a sunflower stem or a linden petiole. Make the section as thin as possible. Place it in a chloral hydrate solution, cover with a coverslip, and clear. Locate the fibers and examine them under low and high magnification. Note the tapered ends of the fibers and the black canal visible in the longitudinally cut fibers. Tiny canals—pits—extend from the canal through The cell wall. The fiber wall is heavily thickened.

Sketch groups of fibers in cross and longitudinal sections, as well as an individual fiber in a longitudinal view. Label and caption the drawings. Describe the research results.

Task 3.

Prepare a temporary slide of a transverse section of tree bark and examine the microstructure of stone cells (sclereids).

Place a transverse section of oak bark in a drop of chloral hydrate, cover with a coverslip, and clear it. Using low magnification, locate a group of stone cells (they will appear silvery), then switch to high magnification to examine their structure. Pay attention to the heavily thickened cell walls and dark cell lumens, from which branched pits extend and connect with the pits of adjacent cells.

Draw a group of stone cells under high magnification. Label and annotate the drawing. Draw conclusions regarding the work performed.

Task 4.

Prepare a temporary slide of a Cytology/practical/54.html">Longitudinal section of a stem and examine the microstructure of Vascular Tissues.

Cut a thin longitudinal section of a sunflower or pumpkin stem (cutting through a vascular bundle visible to the naked eye). Prepare the slide using chloral hydrate. After clearing, examine it under low and high magnification to locate vessels and study their structure. Pay attention to the various types of secondary wall thickenings in vessels (annular, spiral, scalariform, reticulate, pitted, and porous). Just above the vessels, locate sieve tubes and their companion cells. Under high magnification, draw the xylem vascular tissues—Different types of vessels and tracheids (tracheids resemble fibers but feature bordered pits)—as well as the phloem conducting elements, namely sieve tubes and companion cells.

Label all Components of the tissues in the drawing and provide appropriate annotations. Draw conclusions based on the conducted research.

Task 5.

Prepare a temporary slide of a transverse section of a stem and examine the microstructure of vascular tissues.

Prepare a thin transverse section of a monocot stem (e.g., corn) and a dicot stem (e.g., pumpkin or sunflower). Prepare the slide in a chloral hydrate solution and clear it. Under low magnification, locate the vascular bundles, then examine their components—xylem and phloem—under high magnification. Note the large size of the vessels and their thickened walls. Pay special attention to the phloem: in the corn stem, phloem elements are arranged in a checkerboard pattern due to the alternation of sieve tubes and companion cells (monocots lack phloem parenchyma). In dicot stems, this alternation is absent because phloem parenchyma is present. Locate the sieve plates within the sieve tubes. Note that companion cells appear darker than sieve tubes because they retain all their Organelles.

Under the instructor's supervision, perform a Lignin test. Blot the sections dry with filter paper, apply phloroglucinol, and after 2 minutes, apply concentrated acid (handle with extreme care!). Examine under the

microscope and observe the crimson coloration of the lignified walls of xylem elements. Using high magnification, draw a fragment

of the xylem and phloem (separately for monocot and dicot plants). Label and annotate the drawings. Draw conclusions regarding the composition of xylem and phloem in monocots and dicots, as well as the qualitative test for lignin.

IV. Research objects: iris roots, buttercup or valerian roots, corn stem, pumpkin stem, lily-of-the-valley rhizome, fern rhizome.

Materials and equipment: plant organ specimens for temporary slide preparation, permanent slides of plant Organs, microscopes, microscope slides and coverslips, forceps and dissecting needles, drawing book, charts: "Radial bundle of a monocot plant"; "Radial bundle of a dicot plant"; "Closed collateral bundle of corn"; "Open bicollateral bundle of pumpkin"; "Centrophasal (centrophloem) bundle of lily-of-the-valley rhizome"; "Centroxylem bundle of fern rhizome"; colored pencils.

Task 1.

Prepare a temporary slide of a transverse section of a monocot root and examine the structure of a radial vascular bundle.

Prepare several transverse sections of an iris root, place them in a chloral hydrate solution on a glass slide, cover with a coverslip, and clear. Examine under low magnification. Locate the vascular bundle in the center of the organ. Observe that the xylem is arranged in radii, while the phloem occupies the spaces between the xylem radii. Count the number of xylem radii (each originating with a large vessel) and verify that there are more than 5, meaning the bundle is polyarch. Note the complete absence of cambium. Examine the phloem under high magnification. Pay attention to the checkerboard arrangement of the phloem elements, which occurs because monocots lack phloem parenchyma.

Draw a diagram of the Anatomical Structure of the radial polyarch bundle based on low-magnification observations. Label and annotate the drawing. Draw appropriate conclusions.

Task 2.

Prepare a temporary slide of a transverse section of a dicot root in the absorption zone and examine the structure of a radial vascular bundle.

Make several transverse sections of a buttercup or valerian root and prepare a slide in a chloral hydrate solution. Clear and examine under low magnification. Observe the tetrarch radial bundle in the center of the organ. Under high magnification, examine the xylem and phloem. Note that the xylem contains very little wood parenchyma, while the phloem does not exhibit a checkerboard cell arrangement due to the presence of phloem parenchyma.

Draw a diagram of the anatomical STRUCTURE OF THE radial tetrarch bundle. Describe the results of the work performed.

Task 3.

Prepare a temporary slide of a transverse section of a monocot stem and examine the structure of a closed collateral vascular bundle.

Prepare a thin transverse section of a corn stem and make a temporary slide using a chloral hydrate solution. After clearing, examine it under

low magnification. Pay attention to the scattered arrangement of the bundles in the stem and their overall shape. Select the most distinct bundle and examine it under high magnification. Note the absence of cambium and the Abundance of bast and wood fibers. In the phloem, the checkerboard arrangement of its elements is clearly visible.

Draw one vascular bundle observed under high magnification, depicting one half as a schematic diagram in the vertical direction and the other half as an anatomical detail. Label and annotate the drawing. Describe the results of your observations.

Task 4.

Prepare a slide of a transverse section of a dicotyledonous plant stem and study the structure of an open bicollateral vascular bundle.

Make a thin section of a pumpkin stem and prepare a slide in chloral hydrate solution. Clear and examine under low magnification. Select the most distinct bundle and study its structure under high magnification. Note the presence of cambium within the bundle and two phloem regions: primary phloem at the bottom of the bundle and secondary phloem located above the cambium. Between them lies the xylem, which is also primary in its lower part, and secondary in the part adjacent to the cambium featuring large vessels, formed by the cambial activity.

Draw a diagram of the anatomical structure of an open bicollateral vascular bundle. Label the cambium, secondary phloem and xylem, as well as primary xylem and phloem on the drawing. Draw appropriate conclusions.

Task 5.

Prepare a slide of a transverse section of a monocotyledonous plant rhizome and study the structure of a concentric centro-phloem vascular bundle.

Prepare several thin transverse sections of a lily-of-the-valley rhizome, place them in chloral hydrate, cover with a coverslip, and clear. Under low magnification, locate the concentric bundles in the central part of the section. Examine the most distinct one under high magnification. Locate the phloem in the center of the bundle and observe the alternating checkerboard pattern of its elements. The xylem surrounds the phloem. Both the phloem and xylem are primary in origin, as there is no cambium in the bundle.

Draw a diagram of the anatomical structure of a concentric centro-phloem bundle or the entire bundle. Label and annotate the drawing. Describe the research results.

Task 6.

Prepare a slide of a transverse section of a

pteridophyte plant rhizome and study the structure of a concentric

centro-xylem vascular bundle.

Cut several thin transverse sections of the rhizome and make a slide from the thinnest one using chloral hydrate solution. Clear and examine under low magnification. Locate the concentric bundles and examine one of them under high magnification. Note that the xylem is located in the center, surrounded by the phloem. Study the structure of the phloem and

xylem, keeping in mind that in pteridophytes, the xylem lacks vessels and the phloem lacks companion cells.

Draw a diagram of the anatomical structure of a concentric centro-phloem vascular bundle. Label the xylem and phloem on the drawing. Draw conclusions from the conducted observations.

Vascular Bundles

In leaves, vascular bundles are visible to the naked eye (as Veins). In the stem, they are embedded within the ground tissue. A vascular bundle originates from the procambium and represents a complex of tissues. This complex comprises two main regions: the xylem (wood), which serves for The transport of water from the roots, and the phloem (bast), which transports dissolved organic nutrients from the leaves. The primary components of the xylem are tracheae and tracheids, accompanied by wood parenchyma and (not always) sieve tubes with companion cells, bast parenchyma, and (also not always) bast fibers (sclerenchyma).

Closed Collateral Vascular Bundle of Corn

(Zea mays)

A thin transverse section is cut from a portion of a corn stem, treated with a solution of phloroglucinol and Hydrochloric acid, and examined in a drop of water under a microscope.

A large number of vascular bundles, located closer to the center of the stem, are visible in the cross-section. Surrounding the bundle, or exclusively on its outer side, we observe a sheath of uniform cells with thickened walls that have turned red from the phloroglucinol solution—this is the sclerenchyma.

Approximately in the middle of the bundle along a single transverse line lie two circular vessels (reticulate or pitted), accompanied by five to six large cells of wood parenchyma; closer to the center are 1-3 vessels of smaller diameter, followed by a large intercellular space or air lacuna formed by the collapse of the early-formed vessels. Surrounding the small vessels and the air cavity is unlignified wood parenchyma consisting of small cells. External to the large vessels lies the phloem. In grasses, it consists of sieve tubes and companion cells arranged in a more or less regular checkerboard pattern. The larger cells are sieve tubes (their contents are usually not preserved in cross-sections, making them appear empty), while the smaller cells with dense contents are companion cells. Other phloem elements are absent in corn stems. All Tissues of the bundle are primary, as they originate from the primary meristem—the procambium.

Corn vascular bundles are somewhat elongated along the radius of the stem, with the xylem positioned toward the center of the stem and the phloem toward the periphery. Such bundles are referred to as collateral. In monocots, the bundles lack a cambium, making them closed.

Open bicollateral bundle of pumpkin (Cucurbita pepo)

Having made a cross-section of the pumpkin, we examine the vascular bundle in transverse section. The conducting elements of pumpkin are characterized by large sizes. The vascular bundles are not reinforced with sclerenchyma; upon Treatment with a phloroglucinol

solution, only the xylem will stain.

In the broad region of the outer phloem, the larger openings of sieve tubes are clearly visible, sometimes blocked by a transverse partition with pores—the sieve plate. Alongside the sieve tubes are small companion cells with dense protoplasm, along with phloem parenchyma cells.

Beyond the phloem (inward from it), a wide layer of cambium is clearly visible as a radial row of small cells, while the large (reticulate-pitted) vessels and secondary xylem parenchyma are arranged in more or less regular radial rows. Toward the center of the stem, the xylem terminates in a group of small vessels (spiral and annular) arranged irregularly—the primary xylem.

Just inward from the primary xylem lies an area of small parenchymal cells resembling cambium. Further inward, sieve tubes and other phloem elements are encountered; the phloem strand adjacent to the primary xylem is termed the inner phloem, or internal bast, as it is located closer to the center of the stem.

Vascular bundles featuring both outer and inner phloem are called bicollateral.

Concentric vascular bundle of lily of the valley (Convallaria majalis)

Examining the cross-section slide, we observe that all vascular bundles are gathered in the center of the organ; distinct concentric bundles are visible in the center, surrounded on all sides by the ground parenchyma. Encompassing the bundle in a ring are large, thick-walled empty cells that stain red with phloroglucinol solution—this is the xylem of the bundle. The tissue located inside the bundle is the phloem, in which larger cells (sieve tubes) can be distinguished, interspersed with smaller cells containing dense contents—companion cells.

Thus, in lily of the valley, the phloem is encircled by the xylem, and the bundle is termed centrohadal, or amphivasal.