1. 9.3 Growth in Plants

2. 9.3 What should I know?

3. “indeterminate” growth
Plant tissue is derived from meristematic tissue
Composed of aggregates of small cells that have the same function of stem cells in animals
Upon division, one cell remains meristematic while the other differentiates
Meristematic cells are “initials”, differentiated cells are “derivatives”
Remember: unlike humans, plants grow throughout their lives! (Determinate vs indeterminate)

4. Plant Tissue: Types
Dermal Tissue- outer covering that protects against physical agents and pathogenic organisms, prevents water loss, may have specialized structures
Ground Tissue- mostly thin-walled cells that function in storage, photosynthesis, support, and secretion
Vascular Tissue- made up of xylem and phloem that carry out long-distance conduction of water, minerals, and nutrients within the plant, and provide support

5. Meristems
**Differentiated based on location
**area of undifferentiated cells which divide by mitosis
Apical Meristem: PRIMARY meristem; occurs at the tips of roots and stems
“shoot apex”
Produces new tissue and causes primary growth through mitosis and cell division
Allows roots to extend into ground and stems to grow towards sunlight
Results in herbaceous, non-wood stems and roots

6. Meristems
**Differentiated based on location
Lateral Meristem: SECONDARY meristem; allow growth and thickness
Most trees and shrubs (aka woody plants) have active lateral meristems
Two types of meristems:
Vascular cambium (produces secondary tissue and lies between xylem and phloem in vascular bundles
Cork cambium (within bark of plant, produces cork cells of the outer bark)

7. Plant Hormones Factors affecting plant growth:
Environmental factors (day length, water availability)
Receptors
Genetic Makeup
Hormones (chemical messengers)
Proteins (receptors) are located in plasma membrane, cytoplasm, nucleus
Upon reception of a stimulus, protein receptor becomes activated, initiating metabolic pathway which produces a hormone.
Hormones move in the plant via phloem– Control plant growth

8. Tropisms Growth or movement to directional external stimuli
May be positive (towards) or negative (away from)
Common stimuli include: chemicals, gravity, touch, light

9. Auxins
Plant hormones that cause the positive phototropism of plant shoots and seedlings
Found in the embryo of seeds, the meristems of apical buds (shoot apex), young leaves

10. TO DO NOW-- Auxins: page 401-403
Complete the reading on auxins and complete questions 7-11 on page 403.
Turn these in/share them with me today!
**The reading is in your if you don’t have your book**
Homework: Micropropogation activity (2 pages)