Section 6 - Plant structures and their functions - Photosynthesis, transport, stomata and transpiration

Question 1

Where does photosynthesis occur in a plant?

Answer 1

Inside chloroplasts which contain chlorophyll which absorb light

Question 2

Word and balanced chemical equation for photosynthesis?

Answer 2

Carbon dioxide + water –Light + chlorophyll–> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2

Question 3

Three factors that affect rate of photosynthesis?

Answer 3

Light intensity, CO2 concentration and temperature

Question 4

What plant can be used to measure the effect of light intensity on the rate of photosynthesis?

Answer 4

Canadian pondweed

Question 5

Inverse square law equation to measure light intensity?

Answer 5

Light intensity ∝ 1 ÷ distance (d)²

Question 6

What will happen to the rate of photosynthesis if temperature is too high? And the temperature it happens to the enzymes?

Answer 6

Enzymes become denatured

45Cº

Question 7

Which two factors don’t affect rate of photosynthesis if they are too high?

Answer 7

Light intensity and CO2 concentration

Question 8

Two types of transport vessels in flowering plants?

Answer 8

Xylem and phloem

Question 9

What makes root hair cells good for absorbing water and mineral ions from the soil?

Answer 9

A large surface area

Question 10

What process is water and mineral ions absorbed by in the root hair cells and why for mineral ions?

Answer 10

Water absorbed by osmosis

Concentration of mineral ions usually higher in cell than in soil so mineral ions absorbed by active transport

Question 11

Structure of phloem tubes?

Answer 11

Made up of columns of elongated living cells with small pores in the end walls to allow stuff to flow through

Question 12

What do phloem tubes transport and through which process?

Answer 12

Transport food substances made in leaves to rest of plant for immediate use or storage (translocation) and this requires energy from respiration. Transport goes in both directions

Question 13

Structure of xylem tubes?

Answer 13

Made up of dead cells joined end to end with no end walls between them and a hole down the middle. They’re strengthened with a material called lignin

Question 14

What do xylem tubes carry and from and to where? What is this movement called?

Answer 14

Carry water and mineral ions from roots to stem and leaves. Movement of water from roots, through xylem and out of leaves is called transpiration stream

Question 15

What is transpiration and what is it caused by?

Answer 15

Loss of water from the plant

Caused by evaporation and diffusion of water from a plant’s surface. Happens mostly in leaves

Question 16

What happens when there’s a shortage of water in the leaf? How does a constant transpiration stream of water occur?

Answer 16

More water drawn up from rest of plant through xylem vessels, replacing loss of water, meaning more water drawn up from roots so there’s a constant transpiration stream of water through plant, which carriers mineral ions that are dissolved in water along it

Question 17

What are stomata and what are they needed for?

Answer 17

Tiny pores on surface of a plant
They allow CO2 and O2 to diffuse directly in and out of a leaf and allow water vapour to escape during transpiration. Needed for gas exchange

Question 18

What are stomata surrounded by and what does this do?

Answer 18

Surrounded by guard cells, which change shape to control size of pore. When guard cells are turgid, stomata are open. When guard cells flaccid, stomata are closed

Question 19

3 environmental factors that affect transpiration rate?

Answer 19

Light intensity, temperature and air flow

Question 20

What happens to the stomata as it gets darker and why?

Answer 20

Stomata begins to close as it gets darker as photosynthesis can’t happen in the dark so they don’t need to be open to let CO2 in. Little water can escape

Question 21

How does a warmer temperature affect transpiration rate?

Answer 21

When it’s warm, water particles have more energy to evaporate and diffuse out of stomata

Question 22

How does air flow affect transpiration rate?

Answer 22

If there’s good air flow, water vapour swept away easily, maintaining low concentration of water in air outside leaf so diffusion happens quickly.

Question 23

What apparatus can be used to estimate transpiration rate? What does it measure

Answer 23

Potometer, measures water uptake by plant

Question 24

Formula for transpiration rate?

Answer 24

Transpiration rate (mm min-1) = distance moved (mm) ÷ time taken (min)

Question 25

What is translocation? What does it require from respiration?

Answer 25

When sucrose, which is made in the leaves, is transported to rest of plant for immediate use or storage. Requires energy from respiration