III: 2 - Growth and development Flashcards
1
Q
Define
growth
A
A permanent increase in size and dry mass by an increase in cell number or cell size or both
2
Q
Define
dry mass
A
3
Q
Define
development
A
An increase in complexity
4
Q
What conditions are required for seeds to germinate?
A
- Water
- Oxygen
- Suitable temperature (warmth)
5
Q
Why is it important for water to enter the seed for it to germinate?
A
Water is needed to activate the enzymes in the seed so that metabolism takes place.
6
Q
Describe an experiment to investigate the conditions needed for a seed to germinate
A
Set up five test tubes with cotton wool and 5-10 seeds, along with the following:
- (cold) Add water, place in the fridge
- (no water) Place in sunlight
- (no oxygen) Add water, add pyrogallol to absorb oxygen OR cover with layer of oil/paraffin so no oxygen gets in, place in sunlight
- (control) Add water, place in sunlight
- (no sunlight) Add water, cover with foil, place in sunlight
Results:
4 & 5 will germinate, the rest will not
7
Q
Describe the steps of germination
A
- The water activates enzymes stored in the seed
- Enzymes start to digest the starch stored in the seed into sugars
- The sugars produced taken to the embryo and is used as an energy source for growth
- The radicle (root) grows first, fixing the seedling into the soil where it can absorb more water
- The seed is now called a seedling
- Then the shoot grows vertically
- Once the shoot grows the first green leaf the seedling becomes fully independent (before that it was depending on its storage materials)
- The plant is now able to photosynthesise and make its own food
8
Q
Explain the changing dry mass of a germinating seed
A
- The germinating seed starch stored in the cotyledon(s) is digested by enzymes (amylase) and the products used for respiration, so dry mass decreases (A)
- Energy is used for growth, so dry mass increases (B)
- Plant grows and begins to photosynthesise, producing more food for growth and storage, causing dry mass to increase further
