PHOTOSYNTHESIS

WHAT IS PHOTOSYNTHESIS?

• Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight into chemical energy.
• There are two types of photosynthetic processes: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygenic photosynthesis is the most common and is seen in plants, algae and cyanobacteria.

THE EFFECT OF TEMPERATURE, LIGHT INTENSITY AND CO2

• The rate of photosynthesis increases as light intensity increases
• Photosynthetic rate reaches plateau at high light levels
• Rate of photosynthesis increases with increase in temperature, but only till optimal temperature is reached.
• High temperatures reduce the rate of photosynthesis
• Photosynthetic rate reaches plateau at high carbon dioxide levels up to a maximum when rate levels off

THE EFFECT OF TEMPERATURE, LIGHT INTENSITY AND CO2 (CONTINUED)

• Light affects the light-dependent stage, at low intensities there is insufficient ATP and NADPH H produced which stops the Calvin cycle operating at maximum rate
• Both light and temperature can be limiting factors, although other factors can be limiting as well
• Temperature affects light-independent stage • temperature affects enzyme activity • less active at low temperatures / maximum rate at high temperatures
• but will then be denatured (as temperature rises further)

THE RATE OF PHOTOSYNTHESIS MEASURED

• • CO2 + H2O --> (CH2O)n + O2/ suitable photosynthesis equation • amount of CO2 absorbed (per unit time) can be measured • increase in biomass (per unit time) can be measured • O2 excretion (per unit time) can be measured methods for measuring the above: • volume of O2 (bubbles) produced per unit time can be measured • dry mass can be measured • increase in starch concentration in leaves (as measured by iodine) • •

THE RATE OF PHOTOSYNTHESIS MEASURED (CONTINUED)

• The rate of photosynthesis measured is relative because some of the CO2 is produced by the plant internally through respiration
• Use of pH indicator can monitor CO2 uptake in water
• The rate of photosynthesis measured is relative because some of the carbohydrates are used internally by the plan for respiration

THE ROLE OF in photosynthesis

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