topic 6 - plant structures and their function

Question 1

what are photosynthetic organisms

Answer 1

The main producers of food and therefore biomass

Question 2

What reaction is photosynthesis

Answer 2

Endothermic

Question 3

What is the equation for photosynthesis

Answer 3

Uses light energy to react carbon dioxide and water to produce glucose and oxygen

Question 4

What is the effect of temperature on the rate of photosynthesis as a limiting factor

Answer 4

• Enzymes needed for photosynthesis work more slowly at low temperatures
• If the plant gets too hot that enzymes it needs for photosynthesis will be denatured
• This happens at about 45°C

Question 5

What is the effect of carbon dioxide on the rate of photosynthesis as a limiting factor

Answer 5

• increasing the carbon dioxide concentration increases the rate of photosynthesis
• as long as light and carbon dioxide are in plenty of or supply then the fact limiting photosynthesis must be temperature

Question 6

What is the effect of light on the rate of photosynthesis as a limiting factor

Answer 6

As the light level is raised, the rate of photosynthesis increases (the rate is directly proportional to light intensity)

Question 7

What is inverse square law

Answer 7

1/distance squared

Question 8

How does light intensity effect rate of photosynthesis (core practicals and how to complete)

Answer 8

• a source of white light is placed at a specific distance from the pondweed
• the pondweed is left to photosynthesise for a set amount of time
• as it photosynthesises, the oxygen released will collect in the gas syringe - allows you to measure the volume of oxygen produced
• experiment is repeated and light source is placed at different lengths from the pondweed

Question 9

How to calculate rate of oxygen production

Answer 9

Volume produced / time taken

Question 10

What and how are variables controlled in core practical

Answer 10

Temperature (controlled by putting the conical flask in a waterbath)
Carbon dioxide concentration

Question 11

What is rate of photosynthesis directly proportional to

Answer 11

Light intensity

Question 12

What is photosynthesis inversely proportional to

Answer 12

The distance of a light source

Question 13

How are root cells adapted to absorb water and mineral ions

Answer 13

• cells of the surface of the plant root grows into ‘hairs’ which stick out into the soil
• each branch of the root will be covered in millions of these microscopic hairs
• gives a plant a large surface area for absorbing water and mineral ions from the soil
• mineral ions are absorbed by active transport/ water via osmosis

Question 14

How are phloem cells adapted to their function in the plant

Answer 14

• made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through
• they transport food substances (sucrose) made it in the leaves to the rest of the plant for immediate use or for storage
• process is called translocation and it requires energy from respiration (transport goes in both directions)

Question 15

How are xylem cells adapted to their function in the plant

Answer 15

• made of dead cells with no end walls and strengthened with a material called lignin
• carry water and mineral ions from roots to the stem and the leaves
• this movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream

Question 16

What is transpiration

Answer 16

Loss of water from the plant

Question 17

How are water and mineral ions transported through the plant by transpiration

Answer 17

• transpiration is caused by the evaporation and diffusion of water from a plants surface
• loss of water creates a shortage of water in the leaf, so more water is drawn up from the rest of the plant through the xylem vessels to replace it
• more water is drawn up from the roots and so there is constant transpiration stream of water through the plant
• the transpiration stream carries mineral ions that are dissolved in the water along with it

Question 18

How to estimate transpiration rate

Answer 18

• using a potometer, record the starting position of the air bubble
• start a stopwatch and record the distance moved by the bubble per unit time

Question 19

How to calculate the rate of transpiration

Answer 19

Distance moved / time taken

Question 20

What is needed for gas exchange

Answer 20

Stomata

Question 21

What is the structure of stomata

Answer 21

• allows carbon dioxide and oxygen to diffuse directly in and out of a leaf
• allow water vapour to escape during transpiration
• surrounded by guard cells

Question 22

What happens when guard cells are turgid (swollen with water)

Answer 22

Open

Question 23

What happens with guard cells when flaacid (low on water and limp)

Answer 23

Closed

Question 24

How does light intensity affect transpiration rate

Answer 24

Brighter the light, greater the transpiration rate
Stomata begins to close when it gets darker

Question 25

How does temprature affect transpiration rate

Answer 25

Warmer it is, faster transpiration rate
Warm = water particles have more energy to evaporate and diffuse out of the stomata

Question 26

How does air flow affect transpiration rate

Answer 26

• better air flow better transportation rate
  If air flow around a leaf is poor, the water vapour just surrounds the leaf and doesn’t move away.
  This means there’s a high concentration of water particles outside the leaf as well as inside it, so diffusion doesn’t happen as quickly. If there’s good air flow, the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf. Diffusion then happens quickly, from an area of higher concentration to an area of lower concentration.