Plant Responses Flashcards
Where are Auxins located?
In the TIP of the shoot. - apical bud
What happens to the Auxins ?
Diffuse downwards towards the roots
Gradient along main axis of the plant
Concentration highest at the tip
What are the functions of auxins?
- Promote growth
2. Apical dominance
How do Auxins promote growth?
Stimulates both cell division and elongation bring about growth
The further away from shoot, more sensitive to auxin concentration ie, need less auxin to bring. Cell elongation
If concentration of auxin to high, elongation will be stopped
How does Auxins cause apical dominance?
When there is a higher concentration of auxins near apical bud, it inhibits growth of higher lateral buds. If developed buds compete with apical tip for light and nutrients
What is apical dominance?
Developed buds compete with apical tip for light and nutrients
What happens at lower part of the plant?
Auxin concentration becomes less, do lower lateral buds produce shoots, which grow into lateral branches - pyramid shape
What happens when apical bud is removed?
Lateral buds will grow, as no longer inhibited by auxins
What is pruning?
Cut off apical bud, so bushier planet will develop
How does auxins bring about tropic movements?
When auxins cause cell elongation on only one side of the stem or root, results in uneven plant growth
What are tropic movements?
Plants grow into more favourable conditions, have to detect where conditions better,alter growth so can move in appropriate condition
What are tropisms?
Growth movements of part of a plant in response to an internal environment
What happens when a plant responds positively or negatively
Positively- grow towards stimulus
Negatively - grow Away
What is phototrisms?
Growth response to a light stimulus
How do shoots respond to light?
Auxins will move away from light source
If light come from one Direction, growing tip moves away from light
Increased concentration makes cells elongate
Shoot bends towards light
What is Geotrism?
Growth movement of part of a plant in response to the gravitational pull of the earth
Why does a shoot bend upwards while root beds downwards?
Shoot- high concentration of auxin, more growth on lower side, result in upward curvature
Root - growth in lower side inhibited by increased concentration of auxin. In top of root when auxin less, elongate, root grow downwards
Which two important hormones are important in growth and development?
Gibberellins
Abscisic acid
What are the functions of Gibberelins?
- Cause elongation of main stem- internodes lengthen
2. Stimulates seed germination
How are Gibberelins different from Auxins?
Stimulate growth of side branches from lateral buds - no apic dom
No part in bending of a shoot- no tropic movements
What is the function of Abscisic acid?
Helps plants adapt to adverse conditions
How do ABA help plants?
Causes stomata to close, reduces loss of water, when low water
Promotes dormancy in seeds and buds- inhibit seeds from germinating when conditions unfavourable
Converts apical bud into dormant state, protection from mechanical
Promotes abscission of leaves, unfavourable conditions
What two defence mechanisms do plants use?
Chemical and physical
How does chemical defence work?
Plants make parts distasteful or poisonous to herbivores
What are some e.g of chem defence?
Digestive enzyme inhibitors
Bitter- tasting chemicals
Toxins
What are digestive enzyme inhibitors?
Fynbos plants
Block digestion and absorption of proteins by herbi
What are bitter-tasting chemicals? E.g alkaloids
Unpleasant to taste, stop herbivore eating after 1st bite
What are the names of toxins?
Cyanogenic glycosides- cassava plants, produce cyanide
Pyrethrins- Pyrethrins flowers, attack nervous system
What are stinging hairs?
On leaves. Cause immediate and severe burning
What are essential oils?
Insect poison
Protect against fungi attack
E.g peppermint, spearmint, basil
What are allergy causing chemicals?
Cause an allergic reaction- excessive salia, mouth irritation
Herbivores- prevent from eating plant again
What are anti- bacterial chemicals?
Help counteract pathogenic bacteria
What are some of the physical defences?
Thorns
Pathogenic bacteria and fungi
What are the functions of thorns?
Reduce browsing by large herbivores, make difficult to get to leavesSlows down feeding rate
E.g kudu, Impala, giraffes, goats
What is the function of pathogenic bacteria and fungi?
Found on thorns
Insert pathogens into body, causing an infection to dangers disease.
What are plant hormones?
Chemicals that regulate plant growth, development and differentiation of cells and tissues