Plant Responses & Hormones Flashcards
What are tropisms?
a directional growth response in plants, in which the direction of the response is determined by the direction of the external stimulus
Examples of tropisms
e.g. phototropism, geotropism, chemotropism &
thigomotropism
Where does plant growth occur?
occurs at the meristems
- apical meristem
- lateral bud meristem
- lateral meristem
- Intercalary meristems
Describe the apical meristem
is at the tip of the roots and shoots
Describe the lateral bud meristem
is present in buds and gives rise to side shoots
Describe the lateral meristem
lateral meristem forms a cylinder outside the roots and shoots and are responsible for the widening of the roots and shoots
Describe the Intercalary meristems
are between nodes and cause shoot elongation
What are plant nodes?
point of attachment of a leaf or a twig on the stem in seed plants
effect of Auxins
causes elongation of shoot cells, while it also inhibits
root cell elongation in order to cause positive geotropism & phototropism
inhibit side-shoot growth (apical dominance) and inhibit leaf abscission
How do auxins work?
s cause protons to be actively transported into spaces in the cell wall, activating expansins that loosen cellulose in the cell wall.
Increasing plasticity of the cell wall for elongation.
Role of Cytokinins
delay leaf senescence. Can also be used commercially in tissue culture to promote bud and shoot growth.
Role of abscisic acid
causes stomatal closure when there is low water availability. It also inhibits seed germination and growth
Role of gibberellins
- cause stem elongation and seed germination.
2. Commercially it can be used in fruit production by elongating the stem
Role of ethene
cause stem elongation and seed germination.
Commercially it can be used in fruit production by elongating the stem, also used to induce seed formation and barley seed
germination
Commercial use of auxins
to prevent fruit drop, produce seedless fruits, as a herbicide and
encourage root growth.
