9.3 PLANT GROWTH Flashcards
What are meristems
Tissue in plant which is undifferentiated
Apical Meristems
Occurs at shoots and root tips and responsible for primary growth (lengthening of plants)
Produces new leaves and flowers
Lateral Meristems
Occurs at the cambium and is responsible for secondary growth (widening of plant)
Production of bark
How does growth occur in the stem of a plant
Growth occurs in sections called nodes with remaining tissue forming inactive auxiliary buds.
How is the growth of the stem controlled
The growth of the stem and formation of nodes is controlled by plant hormones released from shoot apex like auxins.
What does auxin do
Promotes growth in the shoot apex by cell elongation and division
What is apical dominance
Auxins prevent lateral growth meaning plants use all energy to grow upwards towards the light
What is micropropagation
A technique which produces large quantities of identical plants
What is micropropagation used for
Creating virus free strains of plants
Preventing rare plants going extinct
Rapid Bulking
5 key steps of Micropropagation
1) Plant tissue selected from plant and sterilized
2) Tissue sample grown on sterile nutrient agar gel
3) Treated with auxin to stimulate shoot and root development
4) Growing shoots continously divide creating new samples
5) Once root and shoot developed new plant can be planted in soil
What is a tropism
The growth or turning movement in response to an external stimuli
Phototropism
In a stem, the shaded side contains more auxin and grows longer, which causes the stem to grow towards the light
Auxins have the opposite effect on root cells. In a root, the shaded side contains more auxin and grows less - causing the root to bend away from the light.
What does an auxin efflux pump do
Auxin efflux pumps can set up concentration gradients within tissues – changing the distribution of auxin within the plant
These pumps can control the direction of plant growth by determining which regions of plant tissue have high auxin levels
Auxin efflux pumps can change position within the membrane.
Gravitropism
In a root placed horizontally, the bottom side contains more auxin and grows less - causing the root to grow in the direction of the force of gravity.
The opposite happens in a stem. When a stem placed horizontally, the bottom side contains more auxin and grows more - causing the stem to grow upwards against the force of gravity
