Control & Coordination in PLANTS

Question 1

Plants possess communication systems. What do they enable them?

Answer 1

enable them to coodinate the different parts of their bodies

Question 2

what type of plant is Venus flytrap?

Answer 2

carnivorous plant

Question 3

how does venus flytrap get its supply of nitrogen compounds?

Answer 3

by trapping and digesting small animals (mainly insects)

Question 4

what is the specialised leaf of venus flytrap divided into?

Answer 4

two lobes either side of a midrib

Question 5

venus flytrap

what is the colour inside of the lobes?

Answer 5

Red and has nectar-secreting glands on the edges to attract insects

Question 6

venus flytrap

how many sensory hairs ?

Answer 6

each lobe has 3 sensory hairs that respond to being touched

Question 7

venus flytrap

what happens if an insect touches one of the sensory hairs?

Answer 7

if insect touches with enough force, action potentials are stimulated, which travel very fast across the leaf

Question 8

venus flytrap

when action potential are stimulated, what does it cause?

Answer 8

causes the 2 lobes to fold together along th emidrib, capturing the insect

Question 9

How the closure of the trap is achieved

Answer 9

• 1 sensory hair touched with enough force -> Ca2+ ions channels in cells at base of hair are activated
• channels open -> Ca2+ ions flow in and generate receptor potential
• if 2 sensory hairs stimulated within period of 30 sec, or one hair stimulated twice within this period, action potentials will travel across the trap and cause it to close
• when trap open -> lobes of leaf convex, but when trap is triggered, the lobes quickly become concave, bending downwards and causing the trap to shut- result of release of elastic tension in the cell walls

Question 10

venus flytrap

what does sealing the trap require?

Answer 10

ongoing activation of the sensory hairs- the prey trapped inside provides this ongoing stimulation, generating further action potentials

Question 11

venus flytrap

what does further stimulation of the sensory hairs stimulate?

Answer 11

Calcium ions to enter gland cells where they stimulate the exocytosis of vesicles containing digestive enzymes

The trap then stays shut for up to a week to allow the prey to be digested and the nutrients from it to be absorbed by the plant

Question 12

what are plant hormones (also known as plant growth regulators) responsible for?

Answer 12

most communication within plants

Question 13

what are Auxins a type of?

Answer 13

plant growth regulator that influence many aspects of growth, including elongation growth which determines the overall length of roots and shoots

Question 14

what is the principle chemical in the group of auxins made by plants?

Answer 14

is IAA (indole 3-acetic acid) and this chemical is often simply referred to as ‘auxin’

Question 15

where is Auxin (IAA) synthesised in?

Answer 15

the growing tips of roots and shoots (ie. in the meristems, where cells are dividing)

Question 16

Auxin (IAA) is synthesised in the growing tips of roots and shoots (ie. in the meristems, where cells are dividing)
Growth in these meristems occurs in three stages:

Answer 16

• cell division by mitosis
• cell elongation by absorption of water
• cell differentiation

Question 17

what is Auxin (IAA) involved in controlling?

Answer 17

growth by elongation

Question 18

The role of auxin (IAA) in controlling growth by elongation

Answer 18

1. Auxin molecules bind to receptor protein on CSM
2. Auxin stimulates ATPase to pump H+ ions from cytoplasm into cell wall -> acidifies cells wall
3. activates proteins-> expansins- loosen the bonds between cellulose microfibrils
4. K+ channels open, K+ enter cytoplams -> leads to increase in K+ conc in cytoplasm, which decreases water potential of cytoplasm
5. water moves down water potential grad and enters cytoplasm by osmosis via aquaporins
6. increases internal pressure of cells, causes cell wall to stretch
7. cell elongates

Question 19

what is gibberellin a type of ?

Answer 19

plant growth regualtor involved in controlling seed germination and stem elongation

Question 20

When a barley seed is shed from the parent plant what state is it in?

Answer 20

state of dormancy (contains very little water and is metabolically inactive)

Question 21

when barley seed is in state of dormancy what does it allow the seed?

Answer 21

to survive harsh conditions until the cond are right for successful germination
(eg. the seed can survive a cold winter until temperatures rise again in spring)

Question 22

what does a barley seed contain:

Answer 22

An embryo – will grow into the new plant when the seed germinates
An endosperm – a starch-containing energy store surrounding the embryo
An aleurone layer – a protein-rich layer on the outer edge of the endosperm

Question 23

When the conditions are right, the barley seed starts to?

Answer 23

• absorb water to begin the process of germination

Question 24

When the conditions are right, the barley seed starts to absorb water to begin the process of germination.

what does this stimulate?

Answer 24

the embryo to produce gibberellins

Question 25

where does Gibberellin molecules diffuse and what does it stimulate?

Answer 25

diffuses into the aleurone layer and stimulate the cell there to synthesise amylase

Question 26

Gibberellin molecules diffuse into the aleurone layer and stimulate the cells there to synthesise amylase

In barley seeds, it has been shown that gibberellin does this by?

Answer 26

regulating genes involved in the synthesis of amylase, causing an increase in the transcription of mRNA coding for amylase

Question 27

what does the amylase hydrolyse?

Answer 27

• starch molecules in the endosperm producing soluble maltose molecules
• maltose is converted to glucose and transported to the embryo
• this glucose can be respired by the embryo, providing the embryo with the energy needed for it to grow.

Question 28

The role of gibberellin in the germination of a barley seed

Answer 28

1. water absorbed
2. gibberellins synthesised by embryo
3. gibberellin stimualtes aleurone layer cels to synthesise amylase
4. amylase hydorlyses starch to form maltose
5. maltose converted to glucose
6. glucose transported to embryo, providing energy for growth