Primary growth of Roots and Shoots Flashcards
What are the 3 stages of growth?
- Mitosis
- Cell Expansion
- Cell differentiation and maturation
What are apical meristems?
Zones of active division at tips of roots and shoots
What does the apical meristem produce?
- Protoderm: makes dermal tissue
- Ground meristem: makes ground tissues
- Procambium: makes vascular tissues
What are plant meristems?
zones of undifferentiated, perpetually juvenile (immature) cells capable of mitosis
What are the root functions in root primary growth?
Penetrate soil Take up nutrients and water Exclude undesirable materials Transport water and nutrients Transport photosynthate from shoot to root Anchor and support the shoot
True or false: Roots can grow up to 25mm a day or 1 meter in 40 days
True!
True or false: Root depth can exceed tree height especially in arid environments
True!
True or false: Conifers do not have a taproot system
False! They do!
True or false: Monocots have a fibrous root system
True!
How do roots develop?
- First root from the embryo (the radicle) becomes primary root
and develops into tap root in gymnosperms and eudicots - Root apical meristem (under root cap) produces cells in all direction
- Behind apical meristem is the one of elongation. Then zone of differentiation and maturation
- Apical meristem produces protoderm to outside, procambium in center and ground meristem between
- Protoderm produces epidermis
- Some cells expand laterally into root hairs for water and nutrient uptake
What is the xylem?
the center of the root
Where is the primary phloem found?
In patches
What does the endodermis do?
forms a tight and perfect ring, have a strip of wax called suberin as a barrier to control what stays in and out
What does the ground meristem produce?
Cortex
Endodermis
Pericycle
What does the cortex do?
for storage, also involved in lateral transport
What does the endodermis do?
controls flow of materials into the center of the root (stele)
Radical cells walls are suberized forcing all substances to cross a membrane into the protoplasm, or be excluded
What does the pericycle do?
like cortex but patches become meristematic and form new apical meristems for lateral roots
What does the procambium produce?
Primary phloem
Primary xylem
Vascular cambium
What does the primary phloem do?
living cells for transport of food, hormones,
What does the primary xylem do?
dead, hollow cells for upward transport of water, mineral nutrients, etc.
What does the vascular cambium do?
A secondary meristem
What does it mean to be negatively gravitropic?
The stems grow away from light
What is the root cap filled with?
Amyloplast so they can fall
What is the process of gravitropism?
Amyloplsts settle
Interaction with enodplasmic reticulum
Send hormonal signal from the root cap to the zone of elongation
Most cell expansion is in the zone of elongation
Primary roots are positively gravitropic
Primary laterals grow at around 45 degrees
Secondary laterals are indifferent
Mechanism: root cap cells contain amyloplasts that settle with gravity. Hormonal signals (ER Involved) sent to zone of elongation. Greater elongation on upper side causes curvature.
