Download Lab 8: Plant Structure and Reproduction

Biology 213
Name: _____________________________________
Lab 8: Exploring Plant Structure and Reproduction
Objectives:
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Identify the structure and function of the major plant cell and tissue types
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Differentiate between the structures and functions of the vascular tissue
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Describe the organization of tissues and cells in a plant organ and relate this organization to the function of the organ
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Identify the areas of primary and secondary growth in a typical plant root and stem
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Relate the meristems to the type of growth expected in that plant region
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Examine the secondary growth of woody stems
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Describe the major differences that distinguish the roots, stems, leaves and flowers of “typical” monocots and “typical” dicots
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Explore the connection between flowers and fruit
Introduction and Background:
The vascular plants (as a loose grouping) have been evolutionarily successful for hundreds of millions of
years. Their success, in part, is due to their successful adaptation/evolution to a terrestrial environment. Although
we see many adaptations to a terrestrial environment in the avascular plants, the vascular plants “take it to
another level”.
The terrestrial habitat presents many challenges that aquatic algae did not have to deal with. In particular
are the issues of (not an exhaustive list):
1) Lack of support for the plant body (water is a decent support medium)
2) How to get water from the ground and transport it to the upper reaches of the plant
3) How to transport photosynthetic products to the non-photosynthetic parts of the plant
4) How to disperse pollen and seed (not dealt with in this lab per se)
The vegetative plan organs we will focus on in this lab are the results of evolutions and adaptations to the
terrestrial lifestyle. Specifically, we will focus on three organs: stems, roots, and leaves. These organs have many
cell and tissue types in common, and we will begin by considering the cell types and tissue types. By the time you
are looking at slides, you should be familiar with the cells and tissues. (That is a hint to make the lab go smoother!)
Plant Cell and Tissue Types (a brief overview): This is not meant to be an exhaustive primer on plant cell
and tissue types, but instead to point out some of the more common cell and tissue types. (To get a more
complete description and list, consult your textbook.)
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Epidermal cells are typically flattened, rectangular cells that line portions of the plant body.
Specialized epidermal cell extensions include trichomes and root hairs and a specialized epidermal
cell type you will see on the leaves are the guard cells of the stomata. Most epidermal cells have a
waxy cuticle covering to help prevent water loss through the cells and the organs they line.
Parenchyma cells have a primary cell wall and are relatively flexible. They are found throughout the
plant body and are the least specialized of the cells in this list. These cells serve a wide variety of
functions in the plant body (e.g. photosynthesis in the leaf, sugar sap transport in the phloem, starch
storage in some roots, and the fleshy fruit tissue is mostly composed of parenchyma). They are rather
nondescript cells.
Collenchyma cells have thicker cell walls than parenchyma, but retain some flexibility. In general,
they provide support for young growing portions of the plant body. The lack of a secondary cell wall
allows them to support without limiting growth of the plant part.
Sclerenchyma cells contain both primary and secondary cell walls. As such they are great for support
in non-growing regions of the plant. Many of the regions where you will find sclerenchyma cells are
dead at maturity. The cell walls remain as a skeletal support structure. The water-conducting cells of
the xylem tissue are typically sclerenchyma cells.
Primary Meristematic tissues are found in the growing regions of the plant. These tissues consist of small
actively dividing cells (Remember the mitosis lab?). These cells produce the primary tissue types
(epidermal, ground, and vascular) of these growing regions. In general, we can think of the primary
meristem as lengthening these plant parts. (Hint: look in the stem and root tips for the primary
meristems)
Lateral Meristematic tissues are also found in growing regions of the plant. These tissue types (vascular
and cork cambium for instance) are largely responsible for the thickening (secondary growth) of the
plant parts they are found in. (Hint: Look on the sides of stems and roots (in cross-section) for these
tissues).
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Xylem Vascular tissue is generally responsible for moving water and minerals through the plant body.
As we discussed earlier, these cells are often dead at maturity and the cell wall remains act as a
pipeline for water and mineral transport. Tracheids and vessel members are the primary cell types.
Phloem Vascular tissue generally functions in organic nutrient transport in the plant body. Unlike the
xylem tissue, these cells are often “alive” (although some are on life-support supplied by companion
cells!), and use a more complex transport mechanism when compared to water transport.
We will also compare the plant organs of monocots and dicots. Although this is no longer a systematically
significant distinction, it is still important to be familiar with the two basic body types. There are obvious differences
in basic structure and organization in these two body types and these provide an easy, functional way to
compare plants. For more information about monocots and dicots consult your text or your instructor.
General Guidelines
1. Work in a group (more brains and sets of eyes are sometimes better than one).
2. Examine the slides and the plant specimens provided in the lab.
3. Please do not hoard all slides at your lab station, and allow other students to have access to all slides.
4. Use the pictures in the photo atlas and your textbook to guide you through the slides and specimens.
General terms to define and structures to identify: (you don’t have to write out the definitions, but you should be
familiar with them) roots, stems, leaves, shoot system, meristems, primary growth, secondary growth, dermal tissue
system, vascular tissue system, ground tissue system, lignin, parenchyma, collenchyma, sclerenchyma,
herbaceous, woody, endodermis, pericycle, primary xylem, primary phloem, vascular cambium, bundle sheath,
petiole, blade, node, net venation, parallel venation, cuticle, mesophyll (palisade and spongy), and bundle
sheath
Part 1: Structure of the Dicot and Monocot Root
Use illustrations and guides of the herbaceous dicot and monocot roots to help you examine and label the
slides provided
Slides:
Buttercup (Ranunculus)-the herbaceous dicot root
Identify the following: epidermis, cortex, cortical parenchyma, endodermis, stele, pericycle,
primary xylem, primary phloem, and vascular cambium
Corn (Zea mays)-the herbaceous monocot root
Identify the following: epidermis, cortex, stele, pith, pericycle, xylem, and phloem
Root Tip (l.s.)-monocot or dicot
Identify the following: root tip, apical meristem, zone of elongation, epidermis, stele, root hairs
Part 2: Structure of the Dicot and Monocot Stem
Use illustrations and guides of the herbaceous dicot and monocot stems to help you examine and label
the slides provided
Slides:
Alfalfa (Medicago sativa)-the herbaceous dicot stem
Identify the following: epidermis, cortex, parenchyma, chlorenchyma, collenchyma, pith,
vascular bundles, phloem, xylem, vascular cambium
Corn (Zea mays)-the herbaceous monocot stem
Identify the following: epidermis, sclerenchyma, parenchyma, vascular bundles, phloem,
xylem, schlerenchyma fibers
Stem Tip (l.s.)-monocot or dicot
Identify the following: apical meristem, leaf primordium, axillary bud, procambium, ground
meristem
Part 3: Leaf Structure
Within this exercise you will examine the internal and external structure of angiosperm (and conifer) leaves,
and compare the leaf structure of monocots and dicots.
Part A: “Live” Specimens Use the various leaves provided to examine the external structures and
organization. Draw two different representatives and identify the following structures and patterns:
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petiole, blade, node, leaf arrangement (alternate, opposite, whorled), simple or compound
(palmate or pinnate), venation (net or parallel)
Part B: Slides (the microscopic view)
Slides:
Privet (Ligusturum) or Lilac (Syringa vulgaris)-the dicot leaf
Identify the following: upper epidermis, cuticle, stomata, guard cells, mesophyll (palisade and
spongy), veins (xylem and phloem), bundle sheath, sclerenchyma fibers, lower epidermis
Corn (Zea mays)-the monocot leaf
Identify the following: upper epidermis, stomata, guard cells, mesophyll, xylem, phloem,
bundle sheath cells, lower epidermis
Pine Leaf (for comparison)-conifer leaf (needle)
Identify the following: epidermal cuticle, hypodermis, resin ducts, endodermis, vascular
bundles (xylem and phloem), transfusion tissues, mesophyll, stomata
Part 4: Flowers to Fruit
The angiosperms are recognized as the “flowering plants.” In addition to pollen and seeds, the
angiosperms developed two other distinctive traits: 1) flowers, and 2) fruits. Flowers are made up of four main parts:
1) sepals, 2) petals, 3) stamen, and 4) carpels. Many flowers have been modified to attract insect, bird or mammal
pollinators. Modifications include bright colors, scents or nectar rewards.
Angiosperm means “container seed”, and the seeds are found within fruit. Fruit is a development of the
ovary tissue that surrounds the seed. Fruit evolved to aid in dispersal of the seeds. We will be looking at types of
fruits and dispersal mechanisms in Part 4 of this lab.
There will be several demonstration stations set up around the room. Go to each station and examine the
specimens. For each specimen answer the questions indicated at the station. Make whatever drawings and notes
necessary (in your lab notebook) for you to remember the material and to be able to answer the questions.
Station 1: Flowers to Fruits
This area contains a variety of specimens demonstrating the transition from flower to fruit.
After finishing with this station you should be familiar with:
• Identifying floral structures (sepals, petals, stamens, ovary, style, stigma) on developing and mature fruits.
• Tell the difference between an inferior or superior ovary.
Station 2 A and B: Fruit Type & Dispersal
This area contains a variety of fruits and is divided into two parts: fruit type and fruit dispersal.
After finishing with this station you should be familiar with:
• Identifying different types of fruit.
• Determining how a fruit may be dispersed and describing the structural adaptations that support your
determination.
Postlab Questions:
1. In the cross-section of the stem and root, which tissue type was more noticeable: xylem or phloem? Why
do you think this is so?
2. What types of cells provide support for an herbaceous stem?
3. What are some of the functions of the parenchyma cells in a stem? In a root? In a leaf?
4. How did the monocot stem differ from the dicot stem (in cross-section)?
5. How did the monocot root differ from the dicot root (in cross-section)?
6. How did the monocot leaf differ from the dicot leaf (in cross-section)?
7. Where did you typically find the primary meristematic tissue of the stem? What does this illustrate about
the primary growth of a stem?
8.
Where did you typically find the primary meristematic tissue of the root? What does this illustrate about the
primary growth of a root?
9. What is the function of the endodermis of the root? Why is the endodermis important to living life on the
land?
10. You should have found more stomata on the lower portion of the leaf. What is the advantage of having
more stomata on the lower portion of the leaf rather than on the upper portion?