Grains Research and Development

Date: 01.01.2001

C3, C4 the difference is...

An interesting feature of Australia's grasslands is the way the two major perennial grass classifications — C3 and C4 — have evolved to take best possible advantage of the continent's 'freezer to frypan' climate.

There are two different photosynthetic pathways plants can use. Plants using the C3 pathway rely on the enzyme rubisco to fix carbon atoms from carbon dioxide. The first stable product in this process is based on three carbon atoms, hence the C3 pathway.

C4 plants use the enzyme, PEP carboxylase, leading to a four-carbon molecule and the C4 pathway.

As a generalisation, C3 plants are more temperate, preferring cooler, moister conditions — winter active. C4 plants grow better in warmer, dryer conditions. Their mix in the paddock ensures productive growth year-round.

Examples of C3 grasses (common names only) are Plains Grass,* Corkscrew Grass, Wallaby Grass, Common Wheat Grass and Microlaena — as well as winter cereals.

C4 grasses include Kangaroo Grass, Red Grass, Queensland Blue Grass, Native Sorghum, Lovegrass, Warrego Summer Grass, Umbrella Grass, Wire Grass — as well as summer crops like sorghum and maize.

Region North