Plant Growth

Title :

Plant Growth

Author :

Kim Foglia & Kelly Reidell

Number of slides:

19

Slideshow :

Content transcript :

Growth in Plants
* Specific regions of growth: meristems
* stem cells: perpetually embryonic tissue
* regenerate new cells
* apical shoot meristem
* growth in length
* primary growth
* apical root meristem
* growth in length
* primary growth
* lateral meristem
* growth in girth
* secondary growth
Apical meristems
Root structure & growth
Shoot growth
* Apical bud & primary growth of shoot
* region of stem growth
* axillary buds
* “waiting in the wings”
Growth in woody plants
* Woody plants grow in height from tip
* primary growth
* apical meristem
* Woody plants grow in diameter from sides
* secondary growth
* lateral meristems
* vascular cambium
* makes 2° phloem & 2° xylem
* cork cambium
* makes bark
Secondary growth
* Secondary growth
* growth in diameter
* thickens & strengthens older part of tree
* cork cambium makes bark
* growing ring around tree
* vascular cambium makes xylem & phloem
* growing ring around tree
Vascular cambium
* Phloem produced to the outside
* Xylem produced to the inside
Woody stem
Tree trunk anatomy
Where will the carving be in 50 years?
Plant hormones
* auxin
* gibberellins
* abscisic acid
* ethylene
* and more…
Auxin (IAA)
* Effects
* controls cell division
& differentiation
* phototropism
* growth towards light
* asymmetrical distribution of auxin
* cells on darker side elongate faster
than cells on brighter side
* apical dominance
Gibberellins
* Family of hormones
* over 100 different gibberellins identified
* Effects
* stem elongation
* fruit growth
* seed germination
Abscisic acid (ABA)
* Effects
* slows growth
* seed dormancy
* high concentrations of abscisic acid
* germination only after ABA is inactivated or leeched out
* survival value:
seed will germinate only
under optimal conditions
* light, temperature, moisture
Ethylene
* Hormone gas released by plant cells
* Effects
* fruit ripening
* leaf drop
* like in Autumn
* apoptosis
Fruit ripening
* Adaptation
* hard, tart fruit protects
developing seed from herbivores
* ripe, sweet, soft fruit attracts
animals to disperse seed
* Mechanism
* triggers ripening process
* breakdown of cell wall
* softening
* conversion of starch to sugar
* sweetening
* positive feedback system
* ethylene triggers ripening
* ripening stimulates more ethylene production
Apoptosis in plants
* Many events in plants involve apoptosis
* response to hormones
* ethylene
* auxin
* death of annual plant after flowering
* senescence
* differentiation of xylem vessels
* loss of cytoplasm
* shedding of autumn leaves