C3 and C4 photosythesis

The evolution of C3 Photosythesis

Cyanobacteria where the first to C3 photosythesis; Green alge evolved a chloroplast with C3 by endosymbiosis; First land plants evolved to do C3 Photosynthesis

Problems with C3 Photosyntheis

It’s the most ancestral form of photosynthesis; rubisco is inefficient; this inefficency causes more H2O loss, as the plant needs to keep the stomata open longer

Rubisco

The enzyme responsible for fixing CO2; Can sometimes grab oxygen in hot or oxygen rich environments, called photoresperation;

Significant C3 plants

Soybeans; Wheat; Rice; All of these are greatly effected by Climate change due to temp increases

C4 photosynthesis

Evolved as a solution to photorespiration; Uses Pep carboxylase in mesophyll to capture CO2 as PEP → OAA → Malate; Malate then travels to the bundle sheath where C3 photosynthesis takes place, called decarboxylation

important c4 plants

Corn; Sorghum

Benefits of C4 photosynthesis

Stomata open less often and less stomata dencity; higher photosynthetic rates leading to more growth

where did c4 evolve

Tropical grasses at the edge of rainforests; Temperate grasslands with low rainfall and temperature fluctuations;

Can plants be converted to C4 photosynthesis

Yes; rice is being tested to convert to C4; some other solutions include breeding less methane producing varieities, and planting it spaced out

CAM photosynthesis

Open their stomata at night to collect CO2 while it is cold and store it as malic acid in the vacuole; they then convert it into CO2 during the day

CAM photosynthesis at night

PEP + CO2 -> OAA -> malate -> Malic acid

CAM photosynthesis during the day

Malic acid -> malate; malate is then decarboylated to produce CO2

CAM photosynthesis benefits

prevents the stomata from opening during the day when it is hottest; keep CO2 concentration high in the plant during photosynthesis

CMM

Carboxysomoes; found in cyanobacteria;a protein shell that traps CO2 around rubisco to allow for efficient carbon fixation; being tested in other plants