Name: ________________________________________________ Date: ____________ Block: ________
Leaf Structure and Function
Understanding how the structure of a Leaf relates to its environment.
Introduction:
Leaves are the main organs of food production and photosynthesis in green plants. In most plants,
leaves are generally flattened. The flattened leaves have a large surface area for sun exposure. The flattened
part of a leaf is called the blade. A leaf is attached to the stem of the plant by a petiole. The petiole contains
vessels that carry water to the leaf (xylem) and carry food away from the leaf (phloem).
Leaf tissues are grouped into three types: epidermal, mesophyll and vascular (Figure 1). Most leaves
have all the tissues shown in Figure 1. However, some leaves have extra or fewer structures. Differences in
leaf structures are adaptations to the type of environment in which the plant lives.
In this investigation, you are to observe prepared microscopic slides of leaf cross sections. You are to
locate, identify and distinguish the various structures. You are to describe the difference of the three types of
tissues found in the different leaf types.
Figure 1: The structures found in a leaf
Procedures:
Using low and high power of your microscope, examine the slides of the leaf cross sections. Locate the
cuticle, epidermis, veins (xylem, phloem and bundle sheath), palisade and spongy mesophyll, guard cells and
stomata. Reference the sketch you made in class of the cross section of a leaf as well as the one found
above. Record your observations below and answer the specific questions for each type of leaf.
Yucca (Habitat: _________________________________________________________________)
1. Why do the guard cells and the stomata appear to be so small?
____________________________________________________
____________________________________________________
2. Why are the air spaces almost entirely absent?
____________________________________________________
____________________________________________________
Pear in the Sun and in the Shade (Habitat: ____________________________________________)
3. Compare the number of layers and length of the palisade tissue in the sun leaf and shade leaf. How
are they different? __________________________________________________________________
_________________________________________________________________________________
4. Compare the number of layers and length of the spongy tissue in each leaf. How are they different?
_________________________________________________________________________________
Water Lily (Habitat: _____________________________________________________________)
5. Why are the air spaces in the spongy tissue two to four times
larger than those in all other leaves? ______________________
___________________________________________________
6. On which layer of the epidermis, upper or lower, are the guard
cells and stomata found? ____________________ why are they
found here? ________________________________________
Extension: Sedum Epidermis
Brief Notes in the space provided: