1. Parts of a Plant – Leaves, Roots, Stems and Tissues

2. Function of Leaves Main photosynthetic organ
Broad, flat surface increases surface area for light absorption
Have systems to prevent water loss
Stomata open in day but close at night or when hot to conserve water
Waxy cuticle on surface
System of gas exchange
Allow CO2 in and O2 out of leaf
Elephant Ear Plant

3. Leaf Structure: Overview
Epidermis is a waxy cuticle layer to prevent water loss
Mesophyll (palisade and spongy) takes up most of the leaf layer
Most of chlorophyll for photosynthesis is found here
Moist air spaces allow for gas exchange
Vein carry water, nutrients and gases

4. Leaf Structure: Stoma and Guard Cells
Stoma is a small opening (pore) in the leaf
Open: O2 goes out, CO2 comes in (or water comes in/out)
Closed: No gas exchange (or water stays inside the leaf)
Guard cells – pair controls the opening and closing of stoma
Stoma will be open when climate is moist (water is available). When climate is dry and water is scarce, stoma will close as to prevent drying out of leaf
Pea leaf stomata

5. Leaf Adaptations
Cacti live in dry climates. Leaves would be futile (water loss = death of plant). It has been modified into a spine to prevent water loss
Conifers have thin, short waxy needles instead of leaves. Windy, cold and dry climates would kill the plant. The needles keeps the water in.
Shade plants have more chlorophyll, are thicker, wider and greener. It helps them photosynthesize in low light
Sun-loving plants photosynthesize in high light, so thinner leaves help them with this.

6. Photosynthesis
Process by which plants convert carbon dioxide, sunlight and water to oxygen, sugar and energy
Occurs in chloroplasts of plant cells
Chlorophyll pigment in thylakoid of chloroplast absorbs the light energy to start process

7. Function of Roots Anchor & support plant in ground
Absorb water and minerals
Hold soil in place
Taproots have large main root with shorter branches. Fibrous roots is a network of similarly sized smaller roots (no main root)
Roots do have adaptations. Some of which are:
Grow above-ground to collect more water
Aerial plants can grow downwards on top of standing plants, killing them. This allows the aerial plant to obtain the food, water and light they need for survival.

8. Root Growth Root Hairs (collect water and nutrients)
Zone of Maturation (where root cells become mature)
Zone of Elongation (lengthening of root cells)
Zone of Cell Division (includes Apical Meristem, which generates new cells)
Root cap (protective cap)

10. Function of Stems Support system for plant body
Woody plant stems are hard to bend whereas most flowering plants are softer
Transport system carries water & nutrients (through vascular tissue!)
Holds leaves & branches upright
Stem Growth of Woody Plant:
Looking at the picture below:
What years had the most rain?
What years experienced the worst drought?

11. Stem Adaptations and Uses
Cacti plants have large stems to hold water
Some plants have parts of them stem underground that shoot off to form new plants = reproduction
Practical Uses:
Woody plants for wood, paper, fuel, etc
Maple syrup, root beer, ginger & ginger ale, gum (from Chicle tree)
Dyes, resins, gums and tannins

12. Vascular Tissues
Instead of arteries, veins and capillaries, plants have two types of vascular tissue in stems:
Xylem  thick-celled & dead; transports water and dissolved minerals
Phloem  thin-celled & living; transports sugars and nutrients through stem
Cambium  layers of cells between xylem and phloem that are able to divide
phloem
cambium
xylem
Filler & protective cells 12

13. Vascular Cambium
Vascular cambium forms a continuous cylindrical layer inside the stem that can reproduce
Vascular cambium cells divide to form new xylem cells towards the inside of the stem and new phloem toward the outside of the stem
Form tree rings (wood consists entirely of xylem)
Heartwood: Supports the tree (no transport)
Sapwood: Conducts water and nutrients
Cork: protects the tree
Phloem: transports sugar and nutrients