8/20/2019 The C4 Rice Project

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•Rice is a staple food - more than half the world’s population

•Rice production has to increase by over 50%

•But the rate of growth is decreasing

•C4 Rice project - using efficiency C4 photosynthesis

•All plants using normal photosynthesis (C4) but this can be inefficient since RuBisCo can bind to

oxygen instead of carbon dioxide

•C4 plants still use RuBisCo but they also have a C4 pump

•Mesophyll cells in the leaf capture CO2to produce 4-carbon molecules

•Exported to neighbouring bundle sheath cells, which strip CO2 from the 4-carbon molecules and

feed it to RuBisCO

•converts the 4-carbon molecules to 3-carbon molecules

•C4 can pump up the concentration of CO2 around RuBisCO- more likely that it binds with CO2

and O2

•compared to a turbo-charger•boost to photosynthesis means C4 plants can use less RuBisCO than C3 plants - saves nitrogen

needed to build the protein

•can survive on a lower overall CO2 concentration in the leaf

•Crassulacean Acid Metabolism is similar to C4 - evolved in desert plants

•they open their stomata at night and fix CO2 into 4-carbon molecules

•close their stomata to save water, and release CO2 from the 4-carbon molecules

•four major crops use C4: maize, sugar cane, sorghum and millet

•Rice leaves have widely spaced vascular bundles surrounded by bundle sheath cells.

•large numbers of mesophyll cells- most photosynthesis occurs•Kranz anatomy - inner layer of bundle-sheath cells and outer layer of mesophyll cells

•May have to be bred into rice