Link from the Lab to Today:
Leaf Structure and Function
and AC Leaf Hunter Activity!! (on
Monday)
Copy this into your notebooks.
Leaf Structure
Fig. 1: Cross-Section of a Leaf
Term Definitions:
Epidermis – Outer layer of leaf tissues
(cuticle and leaf hairs)
Cuticle – Waxy protective outer
layer of epidermis that prevents
water loss on leaves, green
stems, and fruits. It’s made of
wax and cutin (a lipid); the
amount of hydrophobic cutin
increases with light intensity.
1) Upper layer: The most
photosynthetically active portion of the
leaf:
• Palisade mesophyll – A tightly packed layer of
parenchyma tissues filled with chloroplasts for
PS.
• Chloroplasts – Sub-cellular, photosynthetic
structures in leaves and other green tissues.
1) Upper layers: The most
photosynthetically active portion of the
leaf:
• Chlorophyll -- a green plant pigment that
captures the energy in light and begins the
transformation of that energy into sugars.
Significance of leaf structure… Why is
there more air space on the bottom?
Why are the chloroplasts more dense
on top?
2) Lower Layer: Gas exchange and
nutrient transport
• Vascular bundle (leaf veins) – Xylem (top -water conduction) and phloem tissues
(bottom – sugar and nutrient transport).
• Spongy mesophyll – Layer of parenchyma
tissues loosely arranged to facilitate
movement of oxygen, carbon dioxide, and
water vapor. It also may contain some
chloroplasts.
2) Lower Layer: Gas exchange and
nutrient transport
• Spongy mesophyll – Layer of parenchyma
tissues loosely arranged to facilitate
movement of oxygen, carbon dioxide, and
water vapor. It also may contain some
chloroplasts.
Gas exchange in the leaf.
2) Lower Layer: Gas exchange and
nutrient transport
• Stomata – Openings in leaves and non-woody
stems that allow for gas exchange (water
vapor, carbon dioxide, and oxygen).
• Guard cells – Specialized kidney-shaped cells
that open and close the stomata (based on
water levels.)
External Features of the leaf:
• Leaf blade – Flattened
part of the leaf
• Petiole – Leaf stalk
• Stipules – Leaf-like
appendages at the base
of the leaf
Copy this into your notebooks.
Fig. 2: Leaf External Structure
Make a heading in your notebooks
entitled ‘’AC Leaf Hunter”
• We will be going outside to document and draw
different types of leaves; take a picture of the leaves
you find to add further details to your drawing once we
return to the classroom.
• Find 6 different types of leaves. Label whether each
one is a monocot or a dicot. Describe the texture of
the leaf; does it have a waxy coating? Are the leaf
veins parallel or branched? Does the top surface have
a waxy feel or appearance? Describe the size,
structure, shape and distribution of the leaves… e.x.
jagged vs. smooth edges, single vs. clustered leaves,
branched vs. un-branched petioles, thickness of the
blade, petiole and veins, etc…
Monocot vs. dicot (parallel vs.
branched veins)
Leaf arrangement on the petiole:
Leaf structure and qualities
• Describe the texture of the leaf; does it have a
waxy coating? Are the leaf veins parallel or
branched? Does the top surface have a waxy
feel or appearance? Describe the size,
structure, shape and distribution of the
leaves… e.x. jagged vs. smooth edges, single
vs. clustered leaves, branched vs. un-branched
petioles, thickness of the blade, petiole and
veins, etc…
Take a picture of the leaf and the plant
after making your sketch…
• We can add more details later and determine
more specifics about the type of leaf, e.x.
• Whether the leaf is simple or complex (and
palmate or pinnate)
Simple vs. Compound leaves
Specific Leaf Shape (advanced)
Making Biological Drawings
(final draft version: 10 marks.)
• Write the species of the leaf on top of the
page (as your title)
• Don’t ‘shade’ a line that’s solid.
• Use pencil; when completed, draw over the
pencil with dark blue or black ink.
• Use a ruler to make all straight lines;
– Drawing on the left side of the page.
– Writing on the right.
Making biological drawings…
Dicot Leaves
• Start a new page, after the rough drawings we
made outside.
• Take your best leaf drawing; compare it with
the picture you took. Make sure you know
what species of leaf it is!
• Label all structures of the leaf; use the leaf
guide to describe the exact leaf shape,
arrangement on the stem, etc…
SC30243 Leaf Hunter Assignment
Drawing of a _____________ leaf.