Dathan C S

Factors affecting rate of photosynthesis

The process of photosynthesis is affected by two types of factors namely:

1.External factors2.Internal factors

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External factors

a. Sunlightb. Temperaturec. Carbon dioxide d. Water ande. Minerals

The three main things affecting the rate of photosynthesis are:

LightTemperatureCarbon dioxide

These three factors are called LIMITING FACTORS.

• Law of limiting factors:

“The overall rate of the process will be limited by the factor which is at the least favorable value”

Light

The rate of photosynthesis increases when light gets brighter

Effect of light

Light response curve-C3 and C4 plants

Light saturation point

Light compensation point• Rate of photosynthesis is equal to rate of

respiration• the light intensity at which the amount of carbon

dioxide released in respiration equals the amount used in photosynthesis and the amount of oxygen used in respiration equals the amount released in photosynthesis, varying in different species of plants and in response to changes in temperature and other environmental factors

TemperatureThe higher the temperature then typically the greater the rate of photosynthesis

Carbon dioxideAn increase in the concentration of carbon dioxide gives an increase in the rate of photosynthesis.

Ethanol plant, Ontario, Canada

Co2 compensation point

• The level at which the oxygen production rate drops to zero is called the compensation point for carbon dioxide.

• it represents the CO2concentration at which CO2 consumption in photosynthesis is balanced by CO2 production in photorespiration

CO2 Saturation Point

• The CO2 Saturation Point of Photosynthesis. At this point increases in CO2 concentration do not cause increases in photosynthetic rate, so factors other than the supply of CO2 must be limiting the photosynthetic process. These factors include:

• a) The supply of light to the leaf.

b) The amount, and turn-over rate, of enzymes involved in the "dark reactions" of photosynthesis.

Co2 compensation point-c3 and c4 plants

Global warming

Global warming and co2

Global warming-C3 and C4• in bright sunlight and warm temperatures, C4 plants grow

faster than C3 ones. yield advantage of C4 plants in hot weather

• C4 plants are better at scavenging carbon dioxide (the source of carbon for sugars) from the air and waste much less water

• whereas rising temperatures benefit C4, rising carbon-dioxide levels do not. In fact, C3 plants get a greater boost from high carbon dioxide levels than C4. Nearly 500 separate experiments confirm that if carbon-dioxide levels roughly double from preindustrial levels, rice and wheat yields will be on average 36% and 33% higher, while corn yields will increase by only 24%.

• C4 has a larger share of the market in weeds. battle against weeds should get easier as carbon dioxide levels rise-because C3 crops can accelerate their growth more than C4 weeds can.

Water

• Water stress leads to stomata closure, less absorption of Co2 and less photosynthetic rate

• No water logging: as it can reduce mineral uptake by active transport which affect the rate of process

Minerals

• All nutrients needed at optimum concentrations

• Pottasium particularly important in stomatal mechanisms so must be at desirable levels

Internal factors

• Chlorophyll• Leaf anatomy• Accumulation of end products• Hormones• Rubisco Performance• Rate of Chloroplast Electron Transport• Enzyme Activity of Calvin Cycle

Internal factors

• Capacity of Metabolite Transport Processes and Carbon Utilization

• Stomatal characteristics etc..

Thnx all