B11 - Gas exchange in Flowering Plants and Excretion in Plants T13-14

Question 1

equation for photosynthesis

Answer 1

light
carbon dioxide + water → glucose + oxygen

Question 2

adaptation of spongy mesophyll for gas exchange

Answer 2

lots of air spaces to allow gases to diffuse in and out of cells
faster, as it increases the surface area to volume ratio

Question 3

adaptation of guard cell for gas exchange

Answer 3

Kidney-shaped cells that open and close the stomata by absorbing or losing water.
When lots of water is available, the cells fill and open stomata

Question 4

adaptation of stomata for gas exchange

Answer 4

Where gas exchange and loss of water by evaporation takes place - opens during the day and closes at night

Question 5

adaptation of leaf for gas exchange

Thin

Answer 5

Short distance of diffusion for carbon dioxide to diffuse into the leaf and oxygen to diffuse out

Question 6

adaptation of leaf for gas exchange

flattened shape

Answer 6

Increases surface area for absorption of light and carbon dioxide

Question 7

plats respire all the time, 24 hours a day, nut photosynthesis can only happen in ____

Answer 7

light

Question 8

is there a net balance of gases during the day and explain

Answer 8

yes
rate of respiration = rate of photosynthesis

so carbon dioxide comes out of the air through photosynthesis and is
replaced through respiration. The opposite occurs for oxygen.

Question 9

why is more oxygen taken into the plants through respiration and more carbon dioxide released at night?

Answer 9

no photosynthesis (no light at night) , to balance out rate of respiration

Question 10

Practical: investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator

Answer 10

1. fill 3 boiling tubes with a leaf and fill with fixed volume (10cm3) on hydrogen carbonate solution
2. one in light, dark and dim light -> leave for 3 hours
3. check colour of solution

Question 11

What is the independent, dependent and controlled variable?

Answer 11

independent = light intensity
dependent = colour of indicator
controlled = volume of solution, leaf species, time, temperature

Question 12

why was a control experiment set up?

Answer 12

the prove that leaf changes CO2 levels

Question 13

colours of hydrogen carbonate indicator in levels of CO2

Answer 13

orange = normal CO2
yellow = increased CO2
purple = very low CO2

Question 14

Results of hydrogen carbonate indicator with leaf in different levels:

Answer 14

light = purple
dark = yellow
dim light = orange
control = orange

Question 15

which light levels do respiration or photosynthesis?
light
dark
dim light

Answer 15

light = PS > R
dark = R only
dim light = PS = R

Question 16

why is limewater not good indicator in this investigation, even though it shows an increase in CO2 levels?

Answer 16

doesn’t show CO2 being removed

Question 17

why were each of the boiling tubes stopped?

Answer 17

to prevent CO2 leaving, and affecting results of investigation