Download LAB INVESTIGATION

LAB INVESTIGATION
ROOTS
Introduction: All plants must be able to absorb various materials from their environment. Many plants
must also anchor themselves to their substratum in order to live. Roots serve both of
these functions. There are a number of kinds of roots both from an external arrangement
and the internal structure. There are plants, such as English ivy and orchids that have
aerial roots. Other plants such as carrots and dandelions have one main tap root with
smaller, almost imperceptible roots branching from it.
Tap roots function not only for anchorage, absorption and conduction, but also for food storage. There
are plants such as grass that have a fibrous root system.
In addition to main roots, there are tiny extensions of the epidermal cells of the roots. These are called
root hairs. In this investigation you are going to look at some kinds of roots and a cross section of a
root.
Materials:
Longitudinal sections through a carrot
Cross-section of a dicot root
Radish seedlings
hand microscope
Compound microscope
Station A: Radish Seedlings
Procedure:
A. Root Hairs –examine the germinating radish seedling. Notice that the root hairs do not grow
from the very tip of the germinating root.
B. Measure (in mm) how far back from the tip of the root to where the root hairs are most
plentiful.
_______________ mm
C. Sketch a single root with root hairs below. Label: seed, root, and root hairs.
Question:
1. Consult your text or another source and look at the microscopic structure of the root hair.
What is the purpose of the root hair and how does its structure aid it in performing this
function?
Station B: Carrot Roots
Procedure:
A. Examine the longitudinal root of a carrot. Notice the central cylinder of stele. Look at the
cut end of the carrot. Notice the location of the central cylinder.
B. Sketch both the longitudinal section and the cross section of the carrot below. Label
epidermis, cortex and stele (center cylinder) for both cross sections.
Longitudinal
Cross section
Questions:
1. What conducting tissues are found in the stele?
2. What adaptations to a dry climate do tap roots have that fibrous roots have not?
3. Why does the carrot plant store food? (other than feeding humans)
Station C: Root Cross Section
Procedure
A. Obtain a slide of Ranunculus (root cross section) and using the compound microscope, focus
on the central cylinder. By consulting your text, you can find the
different structures.
B. Draw the entire root cross section. Label Phloem, Xylem, Cortex and Epidermis. The
blue stained particles in the cortex are starch grains.
Questions:
1. What is the function of the xylem and phloem? Do you think they are connected with the xylem and
phloem of the stem. Why?
2. By what processes do water and minerals enter the root hairs?
LAB INVESTIGATION
STEMS
Introduction: There are basically two kinds of stems—herbaceous and woody. These two kinds can be
further subdivided. There are herbaceous dicot and herbaceous monocot stems. The
perennial (lives more than 2 years) stem is a woody dicot (Basswood or Linden tree) and
the annual stem (lives for 1 year) is a herbaceous dicot (sunflower). For woody stems,
we also use the term hardwood and softwood. Typically we think of hardwoods such as
cherry or oak and soft woods such as pine or spruce.
The basic stem has two major functions. It supports the leaves which carry on
photosynthesis. It also transports materials between the roots and leaves. In woody dicot
stems many of the conducting cells become quite thick or rigid. These rigid cells act as
support. The xylem tissue of woody gymnosperms and angiosperms is the wood used to
construct furniture and houses.
In this investigation you will look at living stems, large sections from stems and cross
sections of two stems. This will aid you in understanding the relationship of structure and
function in a stem.
Materials:
Longitudinal and cross sections of woody angiosperms and gymnosperms.
Samples of various woods.
Woody dicot stem model.
Slide-cross section of annual and perennial stem.
Compound microscope.
Hand microscope.
Station A:
Procedure:
A. Look at one of the half cylindrical sections of a stem. Notice the annual rings and “bark”.
The “bark” is composed of many kinds of tissue including phloem tissue. There is a clearly
defined change in texture and color between the “bark” and xylem tissue, which makes up
most of the sample. Between the phloem and the xylem is cambium tissue, which you can’t
see with the unaided eye.
B. Sketch your section of a stem. Label the bark & xylem tissue.
Station A Questions:
1. What causes annual rings? Consult your text & notes.
2. Name the tissue layers that make up bark.
Station B.
Procedure:
A. Obtain a prepared slide of the Herbaceous and Woody dicot cross sections. The aqua
colored section is the herbaceous dicot and the deeper colored section is the woody
dicot. Observe both carefully noting the differences between the tissue arrangement in
both.
B. Draw the cross sections of the two types of stems below. Label epidermis, cortex, xylem,
phloem, and pith in both. Also label the cambium for the woody dicot cross section.
Herbaceous
Woody
Station B Questions
1. Explain the similarities and differences in the xylem cell arrangement in the
herbaceous and woody stems.
2. Explain the similarities and differences in the phloem cell arrangement in the
herbaceous and woody stems.
3. What materials are transported by xylem and phloem cells and in what directions?
4. What causes an increase in the diameter of woody dicot stems?
5. What is the function of cork and epidermal cells?
6. Is food stored in stems?
LAB INVESTIGATION
LEAVES
Introduction: In this investigation you will look at both living plants and prepared leaf sections in an
attempt to learn the structure and deduce the function of certain leaf parts. You should
note in particular, the ideal way that the leaf is constructed and that leaves are arranged
on the plant to perform their function efficiently.
Materials:
Microscope
Slides of Syringa or Ligustrum
Various classroom plants
Procedure:
Station A: Plant # 1
Procedure
A. Study the arrangement of the leaves on plant #1 from both a side view and a top view. Sketch
the leaf arrangement on the stem.
Questions:
1. Are the leaves arranged on the stem in an alternate pattern around the stem or in an
opposite pattern on the sides of the stem?
2. Explain how this arrangement increases photosynthesis in the plant.
Station B: Plant # 2
Procedure
A. Look at the veins in the leaf on plant #2.
Questions:
1. Are the veins arranged in a parallel or in a net pattern?
2. . Sketch the veins you can easily see.
3. What is the function of the veins?
4. How does the arrangement of the veins help the function?
Station C: Leaf Cross Section
Procedure:
A. Obtain a prepared cross section of a leaf. Note that there is a central or midrib vein. Focus
between this vein and the outer edge of the leaf.
B. Draw a picture of the leaf cross section below. Label the following parts:
a.
b.
c.
d.
e.
upper epidermis
palisade layer
spongy layer
lower epidermis
chloroplasts
(may be hard to see)
f.
g.
h.
i.
guard cell
stomata
vein (xylem phloem)
cutin/ cuticle
C. Location of stomates (lower or upper epidermis): ___________
D. HONORS: Determine the thickness of the leaf. Raw ________
_________ µm
E. HONORS: Determine the width of each of the following cells and record next to the
name.
a. palisade: Raw _________ __________µm
b. spongy: Raw ____________ ________µm
c. epidermis: Raw ___________ _________µm
Questions:
1. How does stomata position aid both their function and the functioning of the plant?
2.Explain how the position of the palisade cells in the leaf aids them in obtaining what they
need for photosynthesis.
3. Explain how the position in the leaf and arrangement of cells in spongy layer aids them in
obtaining what they need for photosynthesis?
3. How does the cutin aid the leaf?
4. What is the advantage to the leaf of being thin and broad?
5.
What disadvantages might being thin and broad have?
More on back! 
6. What kind of a cell arrangement would you expect to find in cold climates or very dry
climates?