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9.3 GROWTH IN PLANTS
9.3 WHAT SHOULD I KNOW?
“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)
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
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
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:
1. Vascular cambium (produces secondary tissue and lies between xylem and phloem in
vascular bundles
2. Cork cambium (within bark of plant, produces cork cells of the outer bark)
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
TROPISMS
Growth or movement to directional external stimuli
May be positive (towards) or negative (away from)
Common stimuli include: chemicals, gravity, touch, light
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
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 email if you don’t have your book**
Homework: Micropropogation activity (2 pages)