In this IBDP Biology blog post, we will be looking at the growth of plants and what micropropagation is, let's get to it!
The Growth of Plant Shoots
Shoot: Stem and leaves
On the shoot there is shoot apical meristems present at the tip
Plant shoots grow by: Mitosis and Cell division
- Some cells stay in the meristem and continue going through the cell cycle producing more cells
- New cells cause the other cells to become displaced to the edge of the meristem
- Cells at the edge stop dividing
- hey undergo rapid growth and differentiation to either become a stem or a leaf
- Leaves are initiated as small bumps at the side of the apical dome
- The leaf primorda (bumps) continue cell division and growth until mature leaves
Tropisms: Growth or movement to directional external stimuli
- Can be positive (towards stimulus) or negative (away from stimulus)
- Common stimuli are: Chemicals, light, touch and gravity
Phototropism: Plant growth in response to light
- Shoots exibit positive phototropism (grow towards light)
- Roots exhibit negative phototropism
- If there are many plants in a single area the seeds must grow towards the light for photosynthesis
- Auxins (hormones) trigger positive phototropism
Micropropogation
Micropropogation: Propogation with very small pieces of tissue taken from the shoot apex of the plant
1. A small piece of tissue is removed from plant that is being cloned. This tissue comes from shoot tip. Tissue is sterilized. All apparatus and growth media must be sterilized to prevent infections - called the aseptic technique
2. Tissue is placed on sterile nutrient agar gel contains high auxin concentration. This stimulates cell growth and devision
3. A callus grows
4. Callus is transferred to nutrient agar gel that contains less auxin but has a lot of cytokinin which stimulates plantlets with roots and shoots to develop
5. The plantlets are seperated and transferred to soil
Produces large numbers of identical plants from stock plants
That is all for this post!
References:
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fib.bioninja.com.au%2Fhigher-level%2Ftopic-9-plant-biology%2Funtitled-2%2Ftropisms.html&psig=AOvVaw1IuSF2Zlz0ypEXQWGrv8-q&ust=1627133541866000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCMjsrIqn-fECFQAAAAAdAAAAABAI
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.microscopemaster.com%2Fmicropropagation.html&psig=AOvVaw2dREPS4saIVN3O8gZanq44&ust=1627133881410000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCLjqqpuo-fECFQAAAAAdAAAAABAD
Drafted by Venetia (Biology)