1. Plant Tissues and Meristems
Most plants have 3 basic types of tissues:
Dermal
Ground
Vascular
All derived from meristematic tissue
Meristematic tissue is composed of aggregates of small cells, which have the ability to divide.
Outer covering which protects against physical agents and organisms. It also prevents water loss
Thin walled cells
Functions: storage, photosynthesis, support, secretion
When the cells divides:
1 stem cell (initials)/1 differentiated cell (derivatives)
Xylem/phloem: carryout long distance conduction (water, minerals, nutrients), provide support
Continually renewed

2. Plant Growth
Plants
Continual pattern of growth
Animals/leaves
Growth ceases at a point
Death:
Annuals (die yearly)
Biennials (2yr cycle)
Perennials (die due to infection, environmental factors)

3. Apical Meristems- often are differentiated based on location within the plant.
Grow tall to increase exposure to light, CO2
1⁰ meristem
-produces new tissues and causes primary growth through mitosis and cell division
2⁰ meristem: increase thickness of stem/root
Results in: Herbaceous, non-woody plants
Results in: Woody plants
Produces cork cells of outer bark
Extends into soil
Produces 2⁰ vascular tissue
- lies between xylem and phloem

4. Plant Hormones
Means of communication within plant
Affect development and growth:
Environmental stimulus (day length/water)
Receptor types (detection of factors)
Genetic makeup
Hormones

5. Plant hormones differ from animal hormones.
-Plant hormones have varying effects depending on the receptor's location.
-Animals ususally have a specialized gland to produce the hormone.
-Plant hormones may be produced throughout the plant.
Process of Hormone signaling
Specific cells have specific receptors
Receive environmental stimulus
Protein receptor activated
Initiates metabolic pathway
Produces hormone (produced throughout plant)
Travel via phloem
Target cell  affects specific area of plant

6. Auxin and Phototropism
Tropisms: growth/movement to directional external stimuli
Positive – towards
Negative - away
Phototropism: response to light
Stems (+)
Roots (-)
Hormone
Increases flexibility of cell walls in young plants
Auxin found in embryo of seed, the meristems of apical buds and young leaves.
Redistributed to shaded side
Creates curvature towards light
Auxin repositions closer to light.
Auxin only works on plants cells that have auxin receptors.
-increase plants flexibility, allowing cells to elongate during growth

7. Auxin and Phototropism
1. Auxin produced in all cells in stem on light side (auxin efflux)
2. Auxin moves by efflux pump action into the cell on the “dark” side of the cell.
3. Auxin and receptor form complex which activates H+ pump
4. The proton pumps H+ into cell wall
5. Causes pH drop; resulting in H-bonds between cellulose fibers – breaking cell wall
6. This results in the elongation of the cells on the side away from the light.

8. Auxin involved with:
Stimulation of cell division in meristematic tissue
Xylem/phloem differentiation
Development of lateral roots
Suppress lateral bud growth when found in apical bud
Stimulate growth of flower parts
Fruit production without pollination
Changes in gene expression

9. Micropropogation
-is used to stimulate existing plant material to produce large numbers of progeny (offspring).
Culture cells from shoot apex
Nutrient agar with growth hormones
Uses:
Rare/endangered plants maintained
Develop virus-free strains
Alter genome to create beneficial plants
Problems:
Extremely expensive
Difficult to maintain pathogen free environment