R2101 4.1 Describe photosynthesis and the factors that affect it

Question 1

Equation for photosynthesis in words

Answer 1

Carbon dioxide+water [light / chlorophyll] = glucose + oxygen

Question 2

What are the inputs of photosynthesis?

Answer 2

Carbon dioxide and water

Sunlight and chloroplasts

Question 3

Water are the outputs of photo synthesis?

Answer 3

glucose and oxygen

Question 4

What is an autotroph?

Answer 4

A producer, can create food within themselves e.g. green plants and algae

Question 5

What is a heterotroph?

Answer 5

A consumer, dependant on outside sources of food. e.g. animals and fungi

Question 6

How does the leaf take in the building blocks of photosynthesis? (3)

Answer 6

1. Sunlight passes through the epidermis to the internal tissue of the leaf to reach the chloroplasts
2. Carbon dioxide enters through the stoma by diffusion
3. Water enters the roots by osmosis then travels up through the vascular tissue into the leaves

Question 6

How does the leaf take in the building blocks of photosynthesis? (3)

Answer 6

1. Sunlight passes through the epidermis to the internal tissue of the leaf to reach the chloroplasts
2. Carbon dioxide enters through the stoma by diffusion
3. Water enters the roots by osmosis then travels up through the vascular tissue into the leaves

Question 7

Output and use of photosynthesis details: Carbohydrates

Answer 7

1. Transported around the plant in the phloem
2. Used in respiration to provide energy for growth
3. Strored as starch that can be used later. Often in the cortex the root
4. Used to produce other plant materials such as cellulose and proteins

Question 8

Output of photosynthesis details: Oxygen

Answer 8

1. Re-used during respiration
2. Released by stomata back into atmosphere

Question 9

What is photosynthesis?

Answer 9

The process in the chloroplasts by which green plants trap light energy from the sun, convert it to chemical energy and use it to produce food in the form of carbohydrates such as sugars and starch

Question 10

Main environmental factors that affect photosynthesis (5)

Answer 10

1. Carbon dioxide
2. Light
3. Adequate temperature
4. water
5. mineral nutrients

Question 11

Carbon Dioxide in photosynthesis (3)

Answer 11

1. Rates in atmosphere at 0.04%
2. In a closed environment levels can fall (greenhouse). Ventilation can rectify this.
3. Some commercial greenhouses actively enrich the atmosphere above normal levels to increase the rate of photosynthesis and crop yield.

Question 12

Light in photosynthesis (4)

Answer 12

1. The greater the light intensity the more photosynthesis takes place
2. Can be increased using artificial lighting
3. Duration of light will effect the rate of photosynthesis - summer v winter
4. Light quality is important if using supplemental lighting - photosynthesis mostly uses red and blue wavelengths of light.

Question 13

What is the photosynthesis saturation point?

Answer 13

Beyond a certain light intensity the rate of photosynthesis falls off as the chloroplasts are fully engaged.

Question 14

What is photosynthetically Active Radiation (PAR)

Answer 14

1. PAR contains the range of wavelengths useful for photosynthesis
2. Between 400nm and 700nm
3. Red and blue wave lengths are the most important
4. Blue wave lengths help vegetative growth
5. Red wave lengths help flowering
6. Green light is not used

Question 15

Temperature in photosynthesis (3)
Including precise amount

Answer 15

1. Optimum temperature for photsynthesis is 25-35C
2. Chemical reactions faster as temperatue rises
3. Minimum of 5C and max of about 45C

Question 16

Water in photosynthesis (2)

Answer 16

1. If there is not an adequate supply of water the stomata close to limit evaporation and carbon dioxide cannot enter the plant
2. Changes in leaf angle in wilting plant also reduce light interception. A visibly wilting plant is not photosynthesising

Question 16

Water in photosynthesis (2)

Answer 16

1. If there is not an adequate supply of water the stomata close to limit evaporation and carbon dioxide cannot enter the plant
2. Changes in leaf angle in wilting plant also reduce light interception. A visibly wilting plant is not photosynthesising

Question 17

Mineral nutrients in photosynthesis

Answer 17

1. Minerals are required by the leaf to produce cholorplasts
2. Plant deficient in iron, nitrogen or magnesium turns yellow (chlorotic) and loses muvh of it ability to photosynthesise.

Question 18

What is the law of limiting factors (Liebig’s Law)

Answer 18

Growth is controlled not by the total resources available but by the scarcest resource or limiting factor

Whatever element is in least supply, controls the rate of photosynthesis

Question 19

Horticultural implications for photosynthesis - helping improve (6)

Answer 19

1. Ventilation / atmospheric enrichment with carbon dioxide in closed enviroments.
2. Keep greenhouse glass clean - 1% loss of light = 1% loss of crop
3. Use supplemental lighting - red and blue wavelengths
4. Insulate with bubble wrap in cold or use heaters
5. To reduce temperatures use blinds, netting, damping down, washed applied to glass
6. Feeding correctly to keep nutrients
7. Site vegetable / fruit gardens where they will get best light

Question 20

Photosynthesis - plants (not leaf) adaptations (4)

Answer 20

1. Shade adapted plants, often evergreen and carry leaves all year round will photosynthesise whenever temperatures and light levels are enough
2. Opportunist plants like bulbs, snowdrops and anemones in woodland areas come up before leaf canopy opens
3. Climbers orientate and lift themselves towards the light
4. Variegated leaves often produce green shoots called reversions. Because they contain more chlorophyll than other parts that are true to type. They are stronger growing and must be removed before they take over. e.g. Pittosporum tenuifolium ‘Silver Queen’