All Plants(hormones,electric Communication)

Question 1

How is the Venus fly trap stimulated to close

Answer 1

1) action potential reaches lobe
2) midrib cells
3) H+ pumped out of cells
4) cell wall loosens
5) calcium pectate dissolves
6) Ca2+ enters cells
7) water enters by osmosis
8) midrib cells expand
9) leaves become concave

Question 2

How is rice water adapted to carry out its function

Answer 2

1) growing taller so top part of leaves are exposed and O2 and CO2 can be exchanged through stomata
2) stems contain aerenchyma cells which are loosely packed allowing gases to diffuse to other parts of the plant
3) have hydrophobic corrugated surface that holds a thin layer of air im contact with leaf surface
4) high ethanol tolerance for anaerobic respiration
5) produce more ethanol dehydrogenase

Question 3

From where is ADH secreted

Answer 3

From posterior pituitary gland

Question 4

How does auxin stimulate cell growth/elongation

Answer 4

1) auxin binds to its protein receptors
2) this stimulates cells to pump H+ in to the cell wall by atpase pump
3) expansins are activated by the decrease in ph
4) they loosen the linkages between cellulose microfibrils
5) by disrupting the non covalent interactions between cellulose microfibrils and surrounding substances
6) potassium ion channels are stimulated to open leading to an inc in potassium ion conc in cytoplasm
7) dec water potenial so water enters through aquaporines

Question 5

How do gibberellins initiate cell growth

Answer 5

1) DELLA protein inhibits transcription factor (PIF)from binding to its promoter
2) absorption of water stimulates the embryo to produce gibberellins
3) diffuse through the aleurone layer and then breakdown the DELLA protein allowing PIF to bind to its promoter
4) transcription of amylase can now take place

Question 6

Describe the homeostasis mechanism of closing and opening of stomata

Answer 6

1) ATP powered proton pumps in the cell surface membrane actively transport H+ out of the guard cell
2) the low H+ conc and negative charge inside the cell causes k+ to open and k+diffuse in to the cell down an electrochemical gradient and lowers the water potential
3) water moves in by osmosis and this increases the volume of the guard cells so that they expand

Question 7

Explain how ABA controls the stomatal closure

Answer 7

1) binds with proton pumps and inhibits them to stop pumping of hydrogen ions out
2) it also stimulates movement of calcium ions in yo the cytoplasm through the cell surface membrane
3) calcium ions acts as a second messenger to activate channel proteins to open allowing -vely charged ions to leave the guard cells
4) this in turn stimulates the opening of potassium ion channels and they move out of the cell
5) at the same time calcium ions also stimulate closure of potassium ion channels that allow them to enter
6) the loss of ions raises the water potential of the cells and water moves out by osmosis
7) guard cells become flaccid and stomata closes

Question 8

Explain how C4 plants are adapted to avoid photo respiration

Answer 8

1)RUBP and rubisco are arranged around the vascular bundles and are called bundle sheath cells
2)no direct contact with air inside the leaf
3)carbon dioxide is absorbed by mesophyll cells
3)contain enzyme PEP carboxylase
4)catalyses combination of CO2 and PEP to form
Oxaloactate
5)oxaloactate is converted to malate
6)CO2 removed from malate and delivered to RuBP and rubisco
7)enzymes in C4 plants have a higher opt temp