Limiting Factors In Photosynthesis

Front 1

What are the optimum conditions for photosynthesis?

(Just name them, no detail)

Back 1

• high light intensity of a certain wavelength

• Temperature around 25°C

• CO2 conc. at 0.4%

• Constant supply of water (not too much or too little)

• (given an adequate amount of Mg2+ and Fe to make chlorophyll, photosynthesis will be reduced otherwise)

Front 2

Explain this optimum condition for photosynthesis?

“High light intensity of a certain wavelength”

Back 2

• light needed - provides the energy for the LDR - the higher the light intensity = the more energy it provides

• only certain wavelengths of light are used for photosynthesis - The photosynthetic pigments chlorophyll a, chlorophyll b and carotene can only absorb the red and blue light in sunlight

Front 3

Explain this optimum condition of photosynthesis?

“temperature around 25°C”

Back 3

• Photosynthesis involves enzymes (ATP synthase, rubisco)

• If temp falls below 10°C, enzymes become inactive

• If temp more than 35°C, enzymes denature

• At high temperatures stomata close (avoid losing too much water) - less CO2 enters the leaf (CO2 conc gradient too small to diffuse through cuticle like oxygen)

Front 4

Explain this optimum condition for photosynthesis?

“CO2 at 0.4%”

Back 4

• CO2 makes up 0.04% of the gases in the atmosphere

• Increasing CO2 conc. to 0.4% gives a higher rate of photosynthesis - because plants use CO2 to make glucose

• CO2 concs. any higher - the stomata start to close

Front 5

Explain this optimum condition for photosynthesis?

“Constant supply of water (not too much/not too little)”

Back 5

• Too little - photosynthesis stops

• too much - soil becomes waterlogged, there is less oxygen in waterlogged soil, roots are unable to respire aerobically, less ATP available for active transport of mineral ions into roots - reduces uptake of mineral ions such as Mg2+ needed to make chlorophyll a

Front 6

Light, temperature and CO2 can also limit photosynthesis all of these things need to be at the right level to allow maximum rate of photosynthesis

If any one of these factors are too low or too high (even if other two are at the perfect level) rate of photosynthesis will be limited.

Back 6

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Front 7

Explain this graph?

Back 7

• between points A and B, the rate of photosynthesis is limited by light intensity (as light intensity increases so can the rate of photosynthesis)

• Point B is the saturation point - Increasing light intensity after makes no difference because something else has become the limiting factor

Front 8

Explain this graph?

Back 8

• Both these graphs level off when light intensity is no longer the limiting factor

• The graph at 25° C levels off at a higher point than the one at 15°C - showing that temperature must have been a limiting factor at 15°C

Front 9

Explain this graph?

Back 9

• Both the graphs level off when light intensity is no longer the limiting factor

• Graph at 0.4% CO2 levels off at a higher point than the one at 0.04% CO2 - CO2 must have been a limiting factor at 0.04% CO2

• the limiting factor is not temperature coz - the temp is the same for both graphs (25)

Front 10

Define - saturation point?

Back 10

Where a factor is no longer limiting the reaction – something else has become the limiting factor

Front 11

Why do agricultural growers (e.g. farmers) care about the factors that limit photosynthesis?

Back 11

Photosynthesis makes lots of important organic compounds that the plant needs.

Limiting the rate of photosynthesis therefore limits the plant growth

• Lowers yield of crops

Front 12

How do agricultural growers (e.g. farmers) create optimum conditions for photosynthesis?

Back 12

In Glasshouses:

• CO2 added to the air (e.g. by burning propane in generator)

• Light can get in through the glass

• lamps provide light at night

• Glasshouses trap heat energy from sunlight which warms the air

• Heaters and cooling systems used - to keep a constant optimum temperature

• Air circulation systems make sure the temperature is even throughout the glasshouse

Front 13

How do agricultural growers (e.g. farmers) create optimum conditions for photosynthesis?

Back 13

In Glasshouses:

• CO2 added to the air (e.g. by burning propane in generator)

• Light can get in through the glass

• lamps provide light at night

• Glasshouses trap heat energy from sunlight which warms the air

• Heaters and cooling systems used - to keep a constant optimum temperature

• Air circulation systems make sure the temperature is even throughout the glasshouse

• use red or blue lights to maximise absorption

Front 14

Why can’t plant photosynthetic pigments absorb green light?

Back 14

Green light is reflected by the plants.

Front 15

Explain why plants grown in an optimum concentration of CO2 will grow taller than plants grown in normal atmospheric conditions?

Back 15

• Plants use CO2 to produce glucose by photosynthesis

• More CO2, means more glucose can be produced, can respire more, more ATP for DNA replication cell division and protein synthesis (i.e. growth)

• increased growth rate

Front 16

Remember - A wood fire burning will increase the CO2 concentration in the air, an electric heater will not.

Back 16

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