Growth and Development Flashcards
Name some of the roles of hormones in trees
- coordination of cell activities and development between tissues
- rate of growth, type of growth
- immunity and defence responses
- timing of flowering and seed formation
- aging, initiation and breaking of dormancy
What are plant growth regulators?
A group of hormones that control growth in plants
List some points about chemical signalling
- Hormone released in a localized area
- alters activity in tissue or other tissue
- effects vary with concentration
- varies with balance of hormone concentrations
How are chemical signals delivered?
primarily through fluids in xylem and phloem
diffusion through tissues when in gas form
List the 5 key plant growth regulators
which are growth promoting?
which are growth inhibitors?
-Growth promoting
Auxin
Giberellin
Cytokinin
-Growth Inhibiting
Abscisic acid (ABA)
Ethylene
List some key features of Auxin
- produced in apical meristems (buds, young leaves)
- transported by parenchyma in phloem
- Promote cell enlargement, stem growth
- Promote cell division in cambium (juvenile wood)
- Initiation of roots
- Cell differentiation
What hormone is used as a synthetic herbicide
synthetic auxin promotes uncontrolled and erratic cell growth which makes it an effective herbicide
What is the role of gibberellin?
- Growth of internodes
- Cell division and elongation
- Etoliation - spindly stems in plants that are light deprived
- Flowering
- Seed germination
- Found in buds, leaves, roots
What is the role of cytokinin
- maintain cell functions and structural processes
- cell division in apical meristems
- cell differentiation in roots
- inhibit lateral root development
- produced in roots
What is the role of ethylene?
- promotes senescence
- gaseous
- promote abscission
- ripening of fruit
- promotes adventitious roots
what is the role of abscisic acid?
- initiates stomatal closure
- inhibits cell division in vascular cambium
- involved in bud initiation
- induction and maintenance of dormancy
- inhibits growth of lateral branches
- produced in buds, fruits and leaves
Explain apical dominance
Apical dominance occurs in select species and it refers to the main stem growing longer than the lateral branches.
simply put: Apical buds suppress the activity of axillary buds
What hormone is related to apical dominance?
Auxin
List and briefly describe the three crown forms
Excurrent
-laterals grow at a wide angle or perpendicular to the stem
Decurrent
-laterals at an angle with stem (broad round crown)
Fastigiate
-branches are long and grow vertically
What is phototropism?
Growth in response to the detection of light
-associated with auxin
Growth toward light
-Positive
Growth away from light
-Negative
