Vascular Tissues & Plant Functional Anatomy

Carly Manz; Chanda Skelton

9 Vascular Tissues & Plant Functional Anatomy

Objectives

Following this lab, students will be able to:

Identify the different cell types of plant vascular tissue and describe how they form the overall tissue structure
Explain how water and sugar are transported in plants
Identify the main types of cells and tissues found in plants and describe their distribution in roots, stems, and leaves
Compare and contrast the arrangement of tissues between different parts of a plant (roots, stems, and leaves) and different phylogenetic groupings of plants
Describe how the cells and tissues of a plant work together to perform the plant’s necessary functions

Contribution Points:

Consult with your TA to receive a stamp at the end of your lab period.

I have completed the necessary tasks required during this week’s lab to earn Contribution Points. I am aware that I may have point(s) deducted from my Contribution Points if my workspace is not appropriately clean at the conclusion of lab.

Resources

Compound Scope Tutorial (video tutorial, linked on Canvas)
Stereomicroscope Tutorial (video tutorial, linked on Canvas)
How to use Preview (video tutorial, linked on Canvas)
Using Leica Software (video tutorial, linked on Canvas)
Biological Science (8th ed.), Freeman et al., 2024. Chapter 34.3–34.4 (pp. 754–763) and Chapter 35 (pp. 766–784).
Botany Photo Atlas (provided for use in lab)
Canvas Resources

Background

This week’s lab is a continuation from last week’s investigation of Plant Cells and Tissues. The focus of this week’s lab will be two-fold. First, you will continue studying Plant Cells and Tissues by investigating Plant Vascular Tissues and water transport in plants. You will then take a broader view of plants by considering the plant as a whole and how all of the cells and tissues work together to keep the plant alive.

You’ll be using your knowledge of plant cells and tissues to think about how they are utilized within the plant; how the cells and tissue types work together to form the plant and to perform the plant’s necessary functions.

In lab you will be looking at plants from the perspective of the three basic plant organs; roots, stems, and leaves. Each of these plant organs performs specific tasks for the plant body as a whole, so each organ will display anatomy that allows the plant to fulfill its function. As you go through this week’s material, think about what function each plant organ is responsible for and think about how the anatomy you observe helps to serve that function.

Plant Vascular Tissue

The vascular system enables the transport of fluids and solutes through the plant, similar to the basic function of the cardiovascular system in animals. The vascular system in plants can also provide some support to the plant. It has two main types of tissue: xylem and phloem. Xylem conducts water and dissolved nutrients from roots to shoots through long columns of tissue. Within the tissue there are specialized cells known as tracheids and vessel elements that participate in transport, and parenchyma cells that provide structural support. Tracheids and vessel elements die at maturity and are then able to conduct water through the plant as long columns of hollowed-out dead cells.

Tracheids are long, slender cells with tapered ends. They have gaps in their secondary cell wall that appear as pits. The water moves between tracheids through these pits. Besides water conduction, tracheids can also provide support to the plant. Vessel elements are shorter and wider than tracheids. Along with pits, they also have perforations in their end walls, allowing the vessel elements to be stacked up along each other like a tube. The perforations in vessels are gaps in both the primary and secondary cell walls.

Phloem tissue is made up of two types of specialized cells: sieve-tube elements and companion cells. Sieve tube elements are long, thin cells that can stack together in a tube, similar to xylem cells. They have perforated ends called sieve plates, which allow sugars and other organic materials to pass between the cells and throughout the plant body. The sieve tube elements are considered living at maturity, but they lack nuclei, chloroplasts and many other organelles. They are connected to companion cells via plasmodesmata. Companion cells contain most organelles and support the sieve tube elements, performing many of their necessary metabolic processes. Phloem tissue also contains more generalized parenchyma cells that provide structural support.

The majority of the specimens you will be observing in lab are provided to you as prepared slides. Not to prepare your own slides (for most specimens) will save you some time this week.

You will be utilizing the microscopes and digital cameras in lab this week. Be mindful when labeling and managing your images to ensure that you do not lose your images or mislabel your photos.

This icon represents a question meant to test your understanding. Answering these questions in the space provided as you go through the lab will help you better understand the topic and study more effectively. Use your text or e-book, botany photo atlases (provided in lab), and appropriate Internet resources to help you.

TA Demonstration

Investigating Water Movement in Bok Choy Petioles

Your TA will play a video tutorial demonstration of water movement in bok choy petioles. In this demonstration, two bok choy leaves (one with the leaves intact, and one where the leaf blades were removed) are cut through the bases of the petioles and placed immediately into a dye solution. The petioles stay in the dye for a short time before they are removed and the movement of the dye through the petioles is examined.

How does the presence of leaf blades affect the rate of water movement through the xylem?

Is this consistent with the evaporation-cohesion-tension model?

1. Xylem – Tracheids

Specimen: Prepared slide of pine stem secondary xylem.

Empty circle for slide activity. — Draw what you see in the space above.

**Figure 9.1.** Tracheids in pine stem macerate prepared slide.

What kind(s) of vascular cells can you identify on this slide?

What are the identifying characteristics of these cells?

2. Xylem – Tracheids and Vessel Elements

**Figure 9.2.** Tracheids and vessel elements in pumpkin stem macerate prepared slide.

Specimen: Prepared slide of pumpkin stem macerate.

What kind(s) of vascular cells can you identify on this slide?

COMPARISON OF SPECIMEN 1 AND SPECIMEN 2

Draw a tracheid in the circle on the left.

Empty circle for slide activity.

Draw a vessel element in the circle on the right.

Empty circle for slide activity.

Which specimen contains both xylem cell types?

What are the structural and/or functional differences between vessel elements and tracheids?

Do these cells contain cytoplasm and/or a nucleus at functional maturity?

What are the functions of vessel elements and tracheids?

3. Phloem Tissues – Sieve Tube Elements and Companion Cells

Specimen: Prepared slide of pumpkin stem longitudinal section. Label parenchyma, sieve tube member, companion cell, and sieve tube plate on the image below.

Microscopic photo with labels. Stem section has several columnar cells in the center with corn kernel-shaped cells to the left and right. — **Figure 9.3.** Phloem tissues in pumpkin stem longitudinal section.

What cell types would you find in the phloem tissue?

What are the functions of these cells?

Do phloem cells contain cytoplasm and/or a nucleus at functional maturity?

4. Xylem and Phloem in Prepared Cross Section

Specimen: Prepared slide of pumpkin stem cross section.

Locate and label the xylem and phloem tissues in images of this cross section below.

Locate and label a sieve plate in images of this cross section below.

Two cell photos. Left: closeup of several small cells clustered around two large circles int he bottom of the frame. Right: clusters of larger, purple dyed cells are surrounded by smaller, lighter colored cells. — **Figure 9.4.** Xylem and Phloem tissues in pumpkin stem cross section prepared slide.

COMPARISON OF SPECIMEN 3 AND SPECIMEN 4

These two specimens give you different views of the same plant. Compare what you see in these two specimens to give you a better idea of how the vascular tissue cells are shaped.

Describe the shapes and functions of the following cell types:

Vessel Element

Sieve Tube Elements

Companion Cell

Xylem and Phloem in Fresh Cross Section

Specimen: Prepare a wet mount slide of a sunflower (Helianthus) or tomato (Solanum) in both cross section and longitudinal section.

**Figure 9.5.** Xylem and Phloem tissue in sunflower stem cross section.

Locate the xylem and phloem in your cross section.

What is the function of xylem?

What is the function of phloem?

Illustration shows phloem, a column-like structure that is composed of stacks of cylindrical cells called sieve-tube elements. Each cell is separated by a sieve-tube plate. The sieve-tube plate has holes in it, like a slice of Swiss cheese. Lateral sieve areas on the side of the column allow different phloem tubes to interact. — **Figure 9.6.** Phloem cell structure.

ROOTS

6. Root Morphology

The figure below illustrates the three major types of roots found in plants; tap roots, fibrous roots, and adventitious roots.

In your own words, describe the differences between the three types of roots below.

**Figure 9.7. Plant Root Types.** Left: dandelion with fleshy tap root; middle: wheat plant with fibrous roots; left: corn crop with adventitious (prop) roots.

7. Radish Seedling Observations ( shoot, root, root hairs, root cap)

Specimen: Make observations of the radish seedlings from the plate provided.

Locate the shoot, root, and root hairs on the radish seedlings. What is the function of the root hairs?

8. Root Anatomy (root cap, region of cell division, region of cell elongation)

Specimen: Prepared slide of longitudinal section of young dicot root (radish, Raphanus).

Locate the root cap, region of cell division, and region of elongation in the images below.

Closeup of a long thin sample with fingerprint-like striations (left) and closeup columnar cells (right) — **Figure 9.8.** Radish root longitudinal section.

9. Eudicot Root Anatomy

Specimen: Eudicot Roots—Prepared slide of buttercup (Ranunculus) cross section. Examine the slide carefully under the compound microscope.

Label the following structures on the image below: epidermis, cortex, xylem, phloem, pericycle, and endodermis.

Closeup photo of ranunculus root cells, a circular selection with a more dense set of cells in the center. — **Figure 9.9.** Ranunculus root cross section.

What is the purpose of the Casparian Strip?

Can you see the vascular cambium, secondary xylem, secondary phloem, and cork cambium in this slide? Why or why not?

Histology slide of Ranunculus root, with sections labeled. A circular collection of cells with several distinct sections. The large circles in the center are vessels, smaller circles are tracheids, clusters are plhloem, and exterior cells of the center are the endodermis. Outside that is the Cortex cells. — **Figure 9.10.** Eudicot root anatomy. The epidermis (not pictured here) is external to the cortex cells. Image Source: Sadierath via Wikimedia Commons, CC BY SA 4.0.

10. Monocot Root Anatomy

Specimen: Monocot Roots— Prepared slide of cross section of corn (Zea mays) root (typical monocot root).

Examine the organization of the vascular tissue of the corn root. How does it differ from a eudicot root?

Label the following structures on the photo below: pith, endodermis, cortex, xylem, and phloem.

Closeup photo of monocot root cells. A dense outer ring of cells encircles a smaller ring of larger cells. Within those in a set of irregular, loosely packed cells. — **Figure 9.11.** Monocot root cross section.

The cross section of a dicot root has an X-shaped structure at its center. The X is made up of many xylem cells. Phloem cells fill the space between the X. A ring of cells called the pericycle surrounds the xylem and phloem. The outer edge of the pericycle is called the endodermis. — **Figure 9.12.** Monocot root anatomy (left side of figure), Eudicot root anatomy (right side of figure). Source: OpenStax Biology, CC BY 4.0.

Stems

11. External Eudicot Stem Structure

Specimen: Woody twig displays (various local tree species)

**Figure 9.13.** External eudicot stem anatomy (twig structure). Shoot morphology by Maria Morrow, CC BY NC 4.0.

Locate the apical buds, lateral buds, leaf scars, and lenticels on the specimens provided in lab.

Why is bark important to woody stems?

What function do the lenticels perform?

12. Herbaceous (Non- Woody) Eudicot Stem Histology

Specimen: Prepared slide of longitudinal section of Coleus terminal bud.

Locate the leaf primordium, vascular bundle, apical meristem, and lateral bud on the photo below.

What is the difference between the terminal bud and the lateral bud? What is similar?

A closeup photo of a meristem cross section, with empty labels. — **Figure** **9.14.** *Coleus* apical meristem cross section.

13. Eudicot Stem Fresh Cross Section

Specimen: Prepare your own cross section of sunflower (Helianthus) or tomato (Solanum) stem.

Carefully examine the slide and locate the pith, epidermis, and vascular bundles on the photo below.

Closeup of a eudicot stem, a circular set of cells with large, bulbous central cells surrounded by pockets of dense cell clusters around the perimeter of the selection. — **Figure 9.15.** Eudicot stem cross section.

14. Eudicot Stem Cross Section Prepared Slide

Specimen: Prepared slide of alfalfa (Medicago) stem cross section.

Carefully examine the prepared slide and locate the pith, epidermis, and vascular bundles on the image below.

Closeup of an alfalfa stem cross section, prepared with dyed purple clusters of small cells around a perimeter of lighter colors, large cells. — **Figure** **9.16.** Eudicot stem (alfalfa) cross section.

15. Monocot Stem Histology

Specimen: Prepared slide of corn (Zea mays) stem cross section.

Carefully examine the prepared slide and locate the ground tissue (parenchyma), epidermis, and vascular bundles on the image on the next page.

Corm stem, with a darl colored perimeter and distributed clusters of dark dyed cell clusters throughout the center of the cell, alongside larger light cells. — **Figure** **9.17.** Monocot stem (corn) cross section.

Referring to Figure 9.18, how is the organization of the vascular tissue in monocot stems different from that in eudicot stems?

Part A is cross section of a dicot stem. In the center of the stem is ground tissue. Symmetrically arranged near the outside of the stem are egg-shaped vascular bundles; the narrow end of the egg points inward. The inner part of the vascular bundle is xylem tissue, and the outer part is sclerenchyma tissue. Sandwiched between the xylem and sclerenchyma is the phloem. Part B is a cross section of a monocot stem. In the monocot stem, the vascular bundles are scattered throughout the ground tissue. The bundles are smaller than in the dicot stem, and distinct layers of xylem, phloem and sclerenchyma cannot be discerned. — **Figure** **9.18.** Monocot stem anatomy compared with Eudicot stem anatomy. Image Source: OpenStax Biology,CC BY 4.0. Adapted by Abbey Elder to add inset photos with labels.

Review of vascular tissue placement in monocot and eudicot stems and roots. Draw a line to match the options on the right to the statements on the left to complete them:

Vascular tissue in monocot roots is:

Vascular tissue in monocot stems is:

Vascular tissue in eudicot roots is:

Vascular tissue in eudicot stems is:

found in the center.

arranged in a ring.

scattered throughout.

Leaves

16. Internal Eudicot Leaf Anatomy

Specimen: Structure of eudicot leaf. Prepared slide of cross section of eudicot leaf AND fresh cross section of eudicot leaf.

Review from Laboratory 8: What is a stoma/stomate? What is the function of the guard cells?

Carefully look at both your own cross section of fresh material and the prepared slide of the eudicot leaf cross section. Describe what you see. Do you notice any differences between the prepared slide and the fresh specimen?

Locate and label the following structures on the photo below: cuticle, epidermis, palisade mesophyll, spongy mesophyll, bundle sheath, vascular bundle, and stoma.

**Figure** **9.19.** Internal eudicot leaf anatomy. Photomicrograph source: Jon Houseman via Wikimedia Commons, CC BY SA 4.0. Adapted by Abbey Elder to add labels.

17. Internal Monocot Leaf Anatomy

Specimen: Structure of monocot leaf. Prepared slide of corn (Zea mays) leaf cross section AND fresh cross section of corn leaf (Zea mays).

Carefully look at both your own cross section of fresh material and the prepared slide of the monocot leaf cross section.

Describe what you see. Do you notice any differences between the prepared slide and the fresh specimen?

Locate and label the following structures on the image below: cuticle, epidermis, bundle sheath, vascular tissue, mesophyll, and stoma.

**Figure 9.20.** Internal monocot leaf anatomy.

18. Internal Anatomy of Gymnosperm Leaf

Specimen: Structure of gymnosperm needle. Prepared slide of cross section of Austrian pine (Pinus nigra) needle.

Carefully examine the slide and describe what you see. What is the general tissue and cell organization of a gymnosperm needle?

What structure(s) do you see in the gymnosperm leaf cross section that you did not see in the monocot or eudicot leaf cross sections?

Do you notice anything special about the stomata in the pine leaf compared to other leaves you observed in lab?

Locate and label the following structures on the image below: epidermis, mesophyll, vascular bundle, stoma, resin duct, bundle sheath.

**Figure 9.21.** Pine needle cross section.

Compare the pine needle (gymnosperm leaf) to the leaves of monocots and eudicots. Specifically look at the epidermal thickness, cross-sectional shape, position of vascular tissue, and presence of resin ducts. Describe what you see in the gymnosperm leaf vs. the monocot/eudicot leaves for each of these characteristics.

NOTE

All materials submitted as a part of your lab assignment must be your own work. This includes both images and answers to questions. Any items suspected of academic dishonesty will be investigated according to course policy.

License

Icon for the Creative Commons Attribution-NonCommercial 4.0 International License