Term 3 Refresh

Question 1

What is transpiration?

Answer 1

The process of water movement through a plant.

Question 2

What are the 4 steps of transpiration?

Answer 2

The water …
1. Gets absorbed by roots (root hair cells)

2. Travels up xylem to leaves
3. Evaporates from leaf cells into airspace. The liquid water in the cells becomes water vapour in the airspace. Liquid water to water vapour is evaporation
4. Diffuses (as water vapour) from airspace in the leaf, through the stoma and into the air (if guard cells are open). Less diffusion when its humid

Question 3

What are the 4 purposes of transpiration?

Answer 3

1. Provides water to keep cells turgid, otherwise plants wilt (flaccid)
2. Replacing water lost through leaves
3. Providing water for photosynthesis
4. Transports minerals

Question 4

What is diffusion?

Answer 4

Diffusion is the net movement of molecules from a higher concentration to a lower concentration.

Question 5

What is osmosis?

Answer 5

Osmosis is a particular type of diffusion. It is the passage of water from a region of high water potential to a region of low water potential through a selectively permeable membrane.
Note that when we say a solution is more concentrated, it usually means the solute is more concentrated and the solvent (which for osmosis is water) is less concentrated.
So, osmosis is a net movement of water from a less concentrated solution to a more concentrated solution through a selectively permeable membrane.
This is the same as saying, it goes from high water concentration to low water concentration which is the same as saying it goes form a high water potential to a low water potential.

Question 6

In an experiment of photosynthesis, how can we control H₂0?

(INDEPENDENT VARIABLES)

Answer 6

1. Limit amount of water available to roots of the plant
2. Decrease water further by increasing diffusion from leaves (wind/fan, humidity)

Question 7

In an experiment of photosynthesis, how can we control sunlight?

(INDEPENDENT VARIABLES)

Answer 7

Control light intensity (light with dimmer) or distance to light or cover leaves.
Note that leaves get their green colour from chlorophyll which absorbs the light needed for photosynthesis.

Question 8

In an experiment of photosynthesis, how can we control the enzymes?

(INDEPENDENT VARIABLES)

Answer 8

Enzymes are required for photosynthesis to take place. If we increase the temp this speeds up a reaction. If we decrease the temp this slows down the reaction. Enzymes denature (and start to stop working) at about 45 degrees.

Question 9

In an experiment of photosynthesis, what are the possible control variables?

(CONTROL VARIABLES)

Answer 9

1. Temperature (effects enzymes)
2. Sunlight (lamp intensity/position or chlorophyll being in light)
3. H₂0 (available at roots, or control diffusion due to wind, humidity or temp)

Question 10

In an experiment of photosynthesis, what can we test for to measure the rate of photosynthesis?
(DEPENDENT VARIABLES)

Answer 10

1. Oxygen: when the leaf is in water, count the bubbles produced
2. Glucose: Plants convert some glucose into starch, check for starch using iodine