PLANTS

Question 1

How do the guard cells work during the NIGHT

Answer 1

-low sunlight + low water available
-water is lost, causes guard cells to become FLACCID
-closing the stomatal pores,
-preventing diffusion of gases in or out
-minimizing water loss through transpiration

Question 2

How do the guard cells work during the DAY:

Answer 2

-lots of water and sunlight available
-water moves into the guard cells
-causes them to become TURGID,
-opens the stomatal pores which allows gases to diffuse in and out of the leaf
-allows photosynthesis

Question 3

Pathway of CO2 during photosynthesis

Answer 3

High concentrations of CO2 outside in the atmosphere compared to inside the leaf ——> CO2 diffuses through stomata into the air pores in the spongy mesophyll —-> diffuses through cell walls + membranes of mesophyll cells ——> dissolves in cytoplasm + diffuses into chloroplasts

Question 4

Gas exchange at night, day and low-light intensities

Answer 4

NIGHT:
-no photosynthesis occurs, only respiration
-net movement of O2 into the leaf, and CO2 out of the leaf

DAY:
-higher rate of photosynthesis than respiration
-net movement of CO2 into the leaf and O2 out of the leaf

LOW-LIHGT INTENSITIES:
-both rates of photosynthesis and respiration are equal
-no net difference in CO2 and O2

Question 5

INVESTIGATING light on gas exchange of a leaf method + results

Answer 5

Label 4 tubes: place 10cm3 of hydrogen carbonate indicator in each
A: no leaf (control) prove that the leaf changes the indicator colour
B: wrap in aluminium foil (dark)
C: wrap in a translucent material (low-light intensity)
D: place in bright light
Place all tube sunder the same bright light, for 30 minutes + bung the top of each

RESULTS:
A: remain orange (CO2 has remained at atmospheric levels)
B: YELLOW: higher CO2 levels (only respiration produces more CO2 above atmospheric levels)
C: orange- both rates are equal, no net difference in CO2 levels
D: PURPLE: more CO2 used in photosynthesis than respiration (CO2 below atmospheric levels)