Plant Structures And Function

Question 1

What are photosynthetic organisms and what is their role?

Answer 1

Photosynthetic organisms are the main producers of food and therefore biomass.

Question 2

What is photosynthesis and what does it involve?

Answer 2

Photosynthesis is an endothermic reaction in plants and algae that uses light energy to convert carbon dioxide and water into glucose and oxygen

Question 3

What are the limiting factors of photosynthesis?

Answer 3

Temperature
light intensity
carbon dioxide concentration.

Question 4

How do temperature, light intensity, and carbon dioxide interact to limit the rate of photosynthesis?

Answer 4

These factors can work together to limit photosynthesis, with one becoming the limiting factor when the others are in abundance.

Question 5

How can the effect of light intensity on photosynthesis be investigated practically?

Answer 5

Potometre practical

Question 6

How does the practical involving pondweed and a potometre to measure photosynthesis work?

Answer 6

1) Place a piece of pondweed (e.g. Elodea) in a beaker of water with sodium hydrogen carbonate (to provide CO₂).
2) Use a lamp at a fixed distance from the pondweed.
3) Allow the pondweed to acclimatise for a few minutes.
4) Count the number of oxygen bubbles released per minute.
5) Repeat the experiment at different distances from the lamp to change light intensity.
6) Optionally, use a gas syringe for more accurate measurement of oxygen volume.

Question 7

How is the rate of photosynthesis related to light intensity and distance from a light source?

Answer 7

It is directly proportional to light intensity and inversely proportional to the square of the distance from the light source (inverse square law).

Question 8

How do substances move into and out of plant cells through which processes?

Answer 8

By diffusion, osmosis, and active transport.

Question 9

How can osmosis be investigated practically in plant cells?

Answer 9

Use potato cells in different sugar/salt solutions and calculate percentage gain or loss in mass.

Question 10

How is the structure of root hair cells adapted to absorb water and minerals?

Answer 10

They have a large surface area and thin walls to increase absorption efficiency.

Question 11

Describe the qualities of xylem

Answer 11

Xylem transports water and minerals from the roots to the rest of the plant in one direction (upward). It is made mostly of dead cells like tracheids and vessel elements, with thick, lignified walls that provide structural support. Xylem is found in the inner part of vascular bundles and forms woody tissue.

Question 12

Describe the qualities of phloem

Answer 12

Phloem transports sugars and nutrients from the leaves to other parts of the plant in both directions. It is made of living cells like sieve tubes and companion cells, with thin cell walls. Phloem is located on the outer part of vascular bundles and forms soft tissue.

Question 13

What is translocation in plants?

Answer 13

The movement of sugars through the phloem from sources to sinks (e.g. leaves to roots).

Question 14

How are water and mineral ions transported through a plant?

Answer 14

By transpiration through the xylem vessels.

Question 15

What is the role of stomata in transpiration?

Answer 15

Stomata control gas exchange and water loss by opening and closing.

Question 16

How is a leaf adapted for photosynthesis and gas exchange?

Answer 16

Large surface area, thin structure, chloroplasts in palisade cells, and stomata for gas exchange.

Question 17

What environmental factors affect the rate of water uptake in plants?

Answer 17

Light intensity, air movement (wind), and temperature.

Question 18

How can the rate of transpiration be calculated?

Answer 18

Using a potometre to measure water uptake over time

Question 19

How are plants adapted to survive in extreme environments?

Answer 19

Through changes like reduced leaf size, thick cuticle, sunken stomata, fewer stomata, thorns to ward off large predators.

Question 20

How do plant hormones control and coordinate growth?

Answer 20

Hormones like auxins control phototropism and gravitropism by stimulating or inhibiting cell growth. This is done as auxins move to the dark sides of the root and stem tips to stimulate growth so it bends towards light , upwards or towards water

Question 21

What are the commercial uses of auxins in plants?

Answer 21

Used in weedkillers as it can cause weeds to grow uncontrollably and use all their energy

Question 22

What are the commercial uses of gibberellins?

Answer 22

Stimulate germination, fruit and flower formation, and production of seedless fruit

Question 23

What is ethene used for commercially in plants?

Answer 23

Causes fruit to ripen faster

Question 25

What is the word equation for photosynthesis?

Answer 25

Carbon dioxide + water → glucose + oxygen.

Question 26

What is the balanced symbol equation for photosynthesis?

Answer 26

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 27

How is a leaf adapted for photosynthesis?

Answer 27

Large surface area, chloroplasts, thin for short diffusion path, stomata.

Question 28

What is transpiration?

Answer 28

The evaporation of water from leaves via stomata.

Question 29

How do guard cells control water loss?

Answer 29

By opening and closing stomata.

Question 30

What are the effects of temperature, light, and wind on transpiration?

Answer 30

All increase transpiration rate. Higher temperature – gives water molecules more energy, so they evaporate faster from leaf cells. Increased light intensity – causes stomata to open wider for photosynthesis, so more water escapes. Lower humidity – increases the concentration gradient between inside and outside the leaf, so more water diffuses out. Increased wind speed – removes moist air from around the leaf surface, maintaining a high concentration gradient for diffusion.

Question 31

What are tropisms?

Answer 31

Growth responses of plants to stimuli (light = phototropism, gravity = gravitropism).