link from the lab to today:

Link from the Lab to Today:

Leaf Structure and Functionand AC Leaf Hunter Activity!! (on Monday)

Copy this into your notebooks.

Leaf StructureFig. 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 AssignmentDrawing of a _____________ leaf.

Description of leaf size, shape and arrangement on the stem

Scale:____ = x cm

SC30243 Leaf Hunter AssignmentDrawing of a Carica papaya Leaf