Bio 103 Lab 5 Plant Anatomy - · PDF fileTYPICAL MONOCOT ROOT, C.S. (CORN ... Microsoft Word - Bio 103 Lab 5 Plant Anatomy.docx

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LABORATORY 5

PLANT ANATOMY

Adapted From: Laboratory 5: Plant Anatomy (Hodgson 2007)

LEARNING OBJECTIVES

At the end of this laboratory, you should be able to:

1. Make proper biological drawings of eudicot and monocot tissues.

2. Differentiate between the three basic tissue types found in plants (parenchyma, sclerenchyma, collenchyma), and describe their function.

3. Identify various structures found in slide preparations of roots, stems and leaves and state the function of the structures.

4. Differentiate between monocots and eudicots in terms of the tissue arrangement of the root, shoot and leaf.

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INTRODUCTION

All herbaceous (non‐woody) flowering plants produce a complete plant body composed of primary tissue derived

from apical meristem. This plant body consists of organs, roots, stems, leaves, flowers, fruits and seeds—and

tissue systems—dermal (epidermis), ground (parenchyma and supportive sclerenchyma and collenchyma) and

vascular (xylem and phloem). In this laboratory, you will observe, and make biological drawings of, the cellular

structure and organization of plant organs and tissues by examining microscope slides.

MATERIALS

Slide of eudicot‐monocot roots

Slide of eudicot‐monocot shoots

Slide of eudicot‐monocot stems

Slide of coleus terminal bud

PROCEDURE

BIOLOGICAL DRAWINGS OF PLANT TISSUES

Appendix III presents a review of microscope use and how to produce proper biological drawings.

*Be sure to have read through the section on how to produce biological drawings in Appendix III before

proceeding.

Log into the RWSL microscope during your reserved time slot.

PLANT PRIMARY GROWTH AND DEVELOPMENT

Plants produce new cells throughout their lifetime as a result of cell divisions in meristems. A meristem is a region

of embryonic tissue primarily concerned with the formation of new cells. The word comes from the Greek word

“to divide”. Tissues produced from apical meristems (at the tip of a root or shoot) are called primary tissues, and

this growth is called primary growth. Primary growth occurs along the plant axis at the shoot and root tips.

Certain meristem cells divide in such a way that one cell product becomes a new cell body and the other remains

in the meristem. Below the zone of active cell division, new cells become enlarged and specialized for specific

functions, resulting, for example, in vessels, parenchyma, and epidermis.

In this first exercise, you will examine a longitudinal section (l.s.) through a terminal bud of Coleus using the

remote microscope.

Use low power to get an overview of the slide, and then increase magnification.

Locate the apical meristem, a dome of tissue nestled between leaf primordial (young developing leaves).

Locate the axillary bud primordia (i.e. in the axil)between the leaf and the stem.

Move the specimen under the microscope so that cells may be viewed at varying distances from the apex

(the tip). The youngest cells are at the apex of the bud, and cells of increasing maturity and

differentiation can be seen as you move away from the apex.

Observe the long, narrow bands of procambium running the length of the section. As this meristematic

tissue divides, some of the progeny cells go on to become xylem and phloem.

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Observe changes in cell size and structure of the vascular system as you move away from the apex and

end with a distinguishable vessel element of xylem, with its spiral cell wall thickening in the stem. You

may need the highest power (400X) to locate these spiral cell walls.

An illustration of a Coleus shoot tip is provided in the worksheet at the end of the lab (Figure 5.1). Label

the structures listed.

CELL STRUCTURE OF PRIMARY TISSUES

Observe the slides of eudicot and monocot stems, roots, and leaves. You are required to make biological drawings.

Drawings must be made in pencil. Each drawing must have a drawing magnification at the bottom of the page;

provide the calculation on the back. Please review the information in Appendix III regarding biological drawings.

ROOTS

TYPICAL EUDICOT ROOT (BUTTERCUP – RANUNCULUS SP.) C.S. = CROSS SECTION

See Biology, 7th ed., 2005, figure 35.13a.

The eudicot root is surrounded by an outer layer of thin‐walled parenchyma cells, called the epidermis. Root hairs may arise from this layer. The epidermis contains no chloroplasts, cuticle or stomata.

In the centre of the root is the vascular cyclinder. It is enclosed by a sheath of cells, called the endodermis. Between the endodermis and the epidermis are the thin‐walled cells of the cortex, a food storage tissue. The cortex takes up most of the area in a root cross‐section.

Within the vascular cylinder are thick‐walled xylem cells which transport water and minerals. Several arms of xylem (usually two to five for a eudicot) radiate from the centre. Xylem cells are larger and their cell walls are stained pink in the prepared slide. Between the arms of xylem are clusters of phloem which carry dissolved nutrients. Phloem cells have thinner cell walls that are stained light blue. The pericycle is a single layer of thick‐walled cells lying just under the endodermis. Lateral roots arise from the pericycle.

Drawing: Make a biological drawing of the vascular cylinder of the eudicot root. The drawing should be made while observing at high power (400X). Calculate drawing magnification and label the following: endodermis, phloem, xylem and pericycle.

TYPICAL MONOCOT ROOT, C.S. (CORN ‐ ZEA MAYS)

See Biology, 7th ed., 2005, figure 35.13b.

The corn prop root is similar to the eudicot root and the same tissues can be identified. Notice the smaller, thicker‐walled cells just below the epidermis that are stained red/pink. These are supportive collenchyma cells.

As in the eudicot root just viewed, the cortex, consisting of mostly large parenchyma cells, is located between the epidermis and the endodermis. In this slide, however, the centre of the root consists of pith, which is also made of parenchyma cells.

The large, open cells just inside of the endodermis are xylem. The phloem cells are generally located between the endodermis and the xylem.

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Drawing: Make a biological drawing of a section of the monocot root that includes a section of vascular tissue. Calculate drawing magnification and label the following structures: cortex, endodermis, phloem, pith and xylem.

B. STEMS

TYPICAL HERBACEOUS EUDICOT STEM, C.S. (SUNFLOWER ‐ HELIANTHUS ANNUS)

See Biology, 7th ed., 2005, figure 35.16a.

In eudicot stems, the vascular tissue is found in bundles arranged in a ring near the outer perimeter of the stem. The phloem lies to the outside of the vascular bundle and the xylem is toward the centre of the stem. Each vascular bundle is shielded by a distinctive bundle cap made of thick‐walled collenchyma cells that are stained a dark red in the prepared slide.

A meristem region, called the cambium, separates the xylem from the phloem. The cambium is the site of cell division: those cells to the inside of the cambium become xylem cells whereas those cells to the outside become phloem cells. A comparatively thin layer of cortex fills in the space between the epidermis and the cambium. The centre of the stem is occupied by pith.

Drawing: Make a biological drawing of a section of the eudicot stem, including at least one vascular bundle. Calculate the drawing magnification and label the following structures: cortex, epidermis, vascular bundle, xylem and phloem.

TYPICAL MONOCOT STEM, C.S (CORN ‐ ZEA MAYS)

See Biology, 7th ed., 2005, figure 35.16b.

In the monocot stem, the epidermis encloses the cortex in which the vascular bundles are scattered. A closeup of a vascular bundle will show xylem, phloem, and an air space.

Directly underlying the epidermis is collenchyma tissue, a form of ground tissue, which provides support for the stem.

Drawing: Make a biological drawing of a section of the monocot stem, including at least one vascular bundle. Calculate the drawing magnification and label the following structures: vascular bundle, xylem, phloem.

C. LEAVES

TYPICAL EUDICOT LEAF, C.S. (LILAC ‐ SYRINGA SP.)

AND TYPICAL MONOCOT LEAF, C.S. (CORN ‐ ZEA MAYS)

See Biology, 7th ed., 2005, figure 35.17c.

Leaves are generally flat, exposing a large surface area to light, and ideally adapted for photosynthesis. Both upper and lower surfaces are lined with flat epidermal cells and are perforated with stomata that allow for gaseous exchange for photosynthesis. The epidermis functions to protect the inside of the leaf from mechanical disturbance and is covered by a waxy cuticle which reduces water loss.

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Stomata are plentiful on the leaf surface, providing for the exchange of gases necessary for photosynthesis. Each stoma (opening) is surrounded by two guard cells that control the opening and closing of the stoma.

In cross‐section, the bulk of the leaf area is occupied by ground tissue called mesophyll.

In eudicot leaves, the mesophyll is divided into two regions, the palisade and the spongy mesophyll. Palisade cells usually contain more chloroplasts than do other leaf cells and therefore carry out most of the photosynthesis. The spongy mesophyll has large air spaces which allows for rapid diffusion of gases through the leaf.

The veins and the midvein of the leaf contain the vascular tissues made up of xylem and phloem cells. These can be recognized in the prepared slide due to their differential staining: xylem stains pink and phloem stains blue. These vascular tissues are continuous with the vascular bundles of the stem. In those plants that carry out C4 photosynthesis, the vascular tissues are surrounded by bundle sheath cells.

One of the characteristics of monocots is that leaf veins are parallel. Each vein has both xylem and phloem tissue and is surrounded by bundle sheath cells. A cap of sclerenchyma cells are located within the bundle sheath and provide support and protection of the vascular tissues. These cell types are best differentiated by viewing a prepared slide of a monocot leaf cross‐section.

Eudicot and monocot leaf cross‐section illustrations are provided in the worksheet at the end of the lab (Figure 5.6 or 5.7). Correctly identify which illustration is of a eudicot leaf and label the following structures: vascular bundle, xylem, phloem, epidermis, cuticle, guard cell, stoma, palisade mesophyll, spongy mesophyll.

Correctly identify which is an illustration of a monocot leaf and label the following structures: vascular bundle, xylem, phloem, epidermis, cuticle, guard cell, stoma, mesophyll.

Examine a prepared slide of monocot and eudicot leaf cross‐sections under the microscope and calculate the actual size for each leaf type. From this information, calculate the ‘drawing magnification’ of the illustrations provided in the worksheet at the end of the lab.

EVALUATION (58 MARKS)

Complete the following worksheet.

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Biology 103 – Lab 5 Worksheet

PLANT ANATOMY

Name _______________________

Plant Primary Growth

1. On Figure 5.1 below, identify the following structures by putting the correct letter in the appropriate space. (4 marks)

FIGURE 5.1. COLEUS STEM TIP (L.S.).

___ stem apical meristem ___ leaf primordia (young)

___ leaf primordia (old) ___ lateral bud meristem (axillary meristems)

___ epidermis ___ procambium

___ ground meristem

E

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Root Tissues

2. Submit biological drawings of monocot and eudicot roots. Be certain to label all structures as indicated and

have a proper title for each drawing (see Appendix III). (8 marks)

3. What is the function of the endodermis in root tissues? What is its importance to the success of plants in a terrestrial environment? (2 marks)

4. Note that the epidermis of a root lacks a cuticle. Why might this be advantageous? (1 mark)

5. Which are larger and more distinct, xylem or phloem tissues? Why? (2 marks)

6.

FIGURE 5.2. ROOT TISSUE (C.S.).

Is this a photomicrograph of a monocot or eudicot root? (1 mark)

_________________

How do you know? (1 mark)

___________________________

___________________________

___________________________

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7.

FIGURE 5.3. ROOT TISSUE (C.S.).

Is this a photomicrograph of a monocot or eudicot root? (1 mark) ___________________________________

How do you know? (1 mark) __________________________________________________________________

Label the following structures on Figure 5.3 (2 marks): pith, cortex, lateral root, endodermis, epidermis.

Shoot Tissues

8. What types of cells provide support to the stem? Where are these cells located in the stem? (2 marks)

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9.

FIGURE 5.4. STEM TISSUE (C.S.).

Label the following structures in the photomicrograph (2 marks): cortex, epidermis, pith, vascular cambium, xylem, phloem.

Is this a monocot or eudicot stem?

(1 mark)

_________________

How do you know? (1 mark)

______________________________

______________________________

10.

FIGURE 5.5. STEM TISSUE (C.S.).

Identify the structures labeled in the illustrations above (2 marks):

1. ___________________ 2. ___________________ 3. ___________________

4. ___________________ 5. ___________________

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Is this a monocot or eudicot stem? How do you know? Be specific. (2 marks)

11. Label the following photo‐illustrations of monocot and eudicot leaves as directed and calculate magnification of the photo images (6 marks)

a.

FIGURE 5.6. LEAF TISSUE (C.S.).

b.

Are the images in Figure 5.6 of a monocot or eudicot leaf? __________________________________________

Examine a prepared slide of a leaf cross‐section under the microscope and calculate the actual size. From this

information, calculate the magnification of Figure 5.6a.

Magnification = ______________

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a.

FIGURE 5.7. LEAF TISSUE (C.S.).

b.

Are the images in Figure 5.7 of a monocot or eudicot leaf? __________________________________________

Examine a prepared slide of a leaf cross‐section under the microscope and calculate the actual size. From this

information, calculate the magnification of Figure 5.7a.

Magnification = ______________

12. List three functions of leaves. (3 marks)

1) __________________________________________________________________________________

2) __________________________________________________________________________________

3) __________________________________________________________________________________

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13. For two of the functions listed above, provide evidence from your observations of leaf structure to support the hypothesis that structure and function are related. Be specific in your examples. (2 marks)

14. In the leaf sections, are more stomata found on the lower surfaces of the leaves than on the upper surfaces? Explain why this is so. (2 mark)

15. The pith and the cortex are made up of parenchyma cells. List four functions of this cell type. (4 marks)

1) __________________________________________________________________________________

2) __________________________________________________________________________________

3) __________________________________________________________________________________

4) __________________________________________________________________________________

16. Compare and contrast the three ground tissues (parenchyma, collenchyma and sclerenchyma) in relation to their form and function. (6 marks).

18. Sclerenchyma includes both sclereids and fibers that make them useful for specific commercial applications. List at least two commercial products that are made using these cells, and the plants associated with these productions. (2 marks).

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Bio 103 Lab 5 Plant Anatomy - · PDF fileTYPICAL MONOCOT ROOT, C.S. (CORN ... Microsoft Word - Bio 103 Lab 5 Plant Anatomy.docx