8.4 Making the most of photosynthesis

Question 1

How can a greenhouse maximize photosynthesis

Answer 1

• Glass or plastic building means that the environment is much more controllable than a garden or a field
• Atmosphere is warmer inside than out
• Speeds the rate of photosynthesis, plants grow faster, fruit earlier, crop better

Question 2

How does the system hydroponics affect photosynthesis

Answer 2

• Control temperature, levels of light and carbon dioxide, get fastest possible rate of photosynthesis
• Plants grown in water with perfect balance of nutrients instead of soil to make sure nothing slows down their growth

Question 3

What are the advantages and disadvantages of greenhouses

Answer 3

Dis
- Electricity and gas are used to maintain light, temperatures and carbon dioxide levels
- Expensive monitoring equipment, needed to maintain conditions within narrow boundaries. Alarms vital if things go wrong
Adv
- Less staff
- Time from seed to harvest is much shorter
- Final crop is larger and cleaner

Question 4

safety precautions for iodine experiment

Answer 4

• ethanol: highly flammable, ensure that bunsen burners are switched off before using it, wear goggles
• iodine will stain hands and clothing
• handle glassware with care

Question 5

name the process that produces starch

Answer 5

photosynthesis

Question 6

explain why the plant stores glucose as starch

Answer 6

• no effect on water balance
• will not wash out leaf

Question 7

how do you de-starch a plant

Answer 7

leave it in the cupboard for two dayse

Question 8

explain why the plant has to be de-starched before starting the experiment

Answer 8

so that any starch present at the end of the experiment has been produced during the experiment

Question 9

explain why you boil the leaf in water

Answer 9

it kills the leaf, stopping further photosynthesis

Question 10

explain why you boil the leaf in ethanol

Answer 10

to remove the chlorophyll and the waxy cuticle

Question 11

explain why you can’t simply add iodine to an untreated leaf to test for starch

Answer 11

• chlorophyll will mask any colour change produced by iodine
• waxy cuticle will not allow iodine to penetrate into the leaf

Question 12

Advantages and disadvantages of hydroponics system

Answer 12

Disadvantages:
- computer software costs a lot of money
Advantages:
- can change carbon dioxide levels, temperature and light levels, and mineral content as plants get bigger
- turnover is fast
- crops are clean and soil-free
- no need to plough or prepare the land
- crops can be grown where land is poor

Question 13

What do farmers use as giant greenhouses now and what do they grow

Answer 13

• plastic polytunnels
• eg 🍅, 🍓,🥔