Types of Photosynthesis C3 C4 CAM

Concepts: Photosynthesis Sugar

Concepts Photosynthesis: CO 2 + Water --> Sugar + O 2 –Photosynthesis is the production of sugar (stored energy) and oxygen using energy from the sun to combine carbon dioxide and water. –CO 2 is brought into plants and O 2 is released from plants through pores (stomata) in their leaves and other tissues. –RUBISCO is the enzyme plants use to undergo photosynthesis. + Solar Energy Stomata

Concepts Respiration: Sugar + O 2 --> CO 2 + Water + E –Respiration is the burning of sugar in the presence of oxygen to release energy stored in the sugar and produces carbon dioxide and water as by-products. Photorespiration : Occurs under high light/heat when RUBISCO tends to react with O 2 (undergoing respiration) rather than CO 2 (undergoing photosynthesis). This slows rates of photosynthesis under high light/heat (this is not what the plant wants to happen). + Energy

Concepts Transpiration : Loss of water out of stomata (pores) of plants during gas exchange (O 2 and CO 2 ) while photosynthesizing and respiring. Water Use Efficiency (WUE): How good a plant is at bringing in CO 2 without losing too much water. In other words it is the ratio of rate of photosynthesis (energy generation) to rate of transpiration (water lost). Stoma

Type 1: C3 Photosynthesis Adaptive Value –More efficient under normal light, temperature, and moisture. How –Uses RUBISCO to collect CO 2 during the day and undergo photosynthesis Who: most plants

Type 2: C4 Photosynthesis Adaptive Value 1 –Photosynthesizes faster under high light/heat conditions. How –Eliminates Photorespiration by using PEP carboxylase (another enzyme) to collect CO 2 during the day and hand delivering CO 2 to RUBISCO so that it can’t react with O 2.

Type 2: C4 Photosynthesis Adaptive Value 2 –Better water use efficiency How –PEP carboxylase is faster at pulling in CO 2 so stomata don’t have to be open as much so don’t lose as much water. Who –many desert summer annuals and grasses

Type 3: CAM Photosynthesis Adaptive Values 1.Better water use efficiency 2.Cam-idling How 1.Uses PEP carboxylase to collect CO 2 during the night (when evaporation rates are less), stores the CO 2 as acid, closes stomata during day when conducts photosynthesis. 2.Can keep stomata closed all the time, using CO 2 from respiration to photosynthesize and O 2 from photosynthesis for respiration. Who: cactuses, agaves, bromeliads

Review of Photosynthesis Types Adaptive Values –C3 photosynthesis –More efficient under normal light, temperature, and moisture. –C4 photosynthesis –Photosynthesizes faster under high light/heat conditions. –Better water use efficiency –CAM photosynthesis –Better water use efficiency –Cam-idling

Review of Photosynthesis Types How (summary – see full explanation in previous slides) –C3 photosynthesis –Uses RUBISCO to collect CO 2 during day. –C4 photosynthesis –Uses PEP carboxylase to collect CO 2 during day. –Delivers CO 2 directly to RUBISCO to eliminate photorespiration and is faster at pulling in CO 2. –CAM photosynthesis –Uses PEP carboxylase to collect CO 2 during night. –Stores CO 2 in form of acid. Allows idling. –Delivers CO 2 directly to RUBISCO to eliminate photorespiration and is faster at pulling in CO 2.

Review of Photosynthesis Types Who –C3 photosynthesis –Most plants –C4 photosynthesis –A variety of plants, especially our summer annuals and many of our grasses –CAM photosynthesis –Cacti, agaves, bromeliads, and others