limiting factors

Question 1

What do plants need to photosynthesize (and grow as fast as they can)?

Answer 1

Light, warmth and carbon dioxide

Question 2

How does light affect the rate of photosynthesis?

Answer 2

If there is plenty of light, lots of photosynthesis can take place; In low light, photosynthesis will stop

Question 3

How does temperature affect the rate of photosynthesis?

Answer 3

As the temperature rises, the rate of photosynthesis increases as the reaction speeds up

Question 4

What happens when the temperature gets too high during photosynthesis?

Answer 4

The enzymes controlling photosynthesis are denatured and the rate of photosynthesis will fall

Question 5

Why does the rate of photosynthesis fall if the temperature get too high?

Answer 5

Most of the enzymes that control photosynthesis are denatured once the temperature rises to around 40–50ºC

Question 6

Why do plants need carbon dioxide?

Answer 6

To make glucose

Question 7

Why does carbon dioxide often limit the rate of photosynthesis?

Answer 7

Because the atmosphere is only about 0.04% carbon dioxide

Question 8

How do carbon dioxide levels affect the rate of photosynthesis?

Answer 8

Increasing the carbon dioxide levels will increase the rate at which photosynthesis takes place

Question 9

Why are carbon dioxide levels the most limiting factor for plants on a sunny day?

Answer 9

The carbon dioxide levels around a plant tend to rise at night, when the plant respires but does not photosynthesize

Question 10

What happens to the carbon dioxide as light and temperature levels increase in the morning?

Answer 10

The carbon dioxide around the plant is used up

Question 11

What occurs the more a plant photosynthesizes?

Answer 11

It produces more biomass and it grows faster

Question 12

How can people artificially control the environment of their plants?

Answer 12

By using greenhouses or polytunnels

Question 13

Why is artificially controlling the plants’ environment important?

Answer 13

The atmosphere is warmer inside than out, speeding up the rate of photosynthesis so the plants grow faster, flower and fruit earlier and produce higher yields

Question 14

What do companies using big commercial greenhouses do to the carbon dioxide levels?

Answer 14

They are increased during the day when light levels are at their highest

Question 15

What do companies using big commercial greenhouses do to the temperature?

Answer 15

They make sure the optimum temperature for enzyme activity is maintained all the time

Question 16

What do companies using big commercial greenhouses do to the light?

Answer 16

Artificial lighting is used to prolong the hours of photosynthesis and to increase the light intensity

Question 17

What can artificial lighting be used for?

Answer 17

It can be used to give year-round production by plants, and to grow plants out of their normal season or out of their normal habitat

Question 18

What are some advantages of using greenhouses to control a plant’s environment?

Answer 18

= Turnover is fast, which means profits can be high
= The crops are clean and unspoilt
= There is no ploughing or preparing the land
= Crops can be grown where the land is poor
= Fewer staff are needed

Question 19

What are some disadvantages of using greenhouses to control a plant’s environment?

Answer 19

= It costs a lot of money

= It takes a lot of energy to keep the conditions stable