What do C3 grasses primarily possess in comparison to C4 grasses?

C3 grasses primarily possess lower water use efficiency compared to C4 grasses due to their distinct photosynthetic pathway. In the C3 photosynthetic mechanism, carbon dioxide is fixed into a three-carbon compound during the process of photosynthesis. This pathway is optimal under cool, moist conditions but becomes less efficient in high temperatures and under drought stress.

C3 plants typically open their stomata more frequently and for longer periods to take in carbon dioxide, which can result in higher water loss through transpiration, leading to lower water use efficiency. In contrast, C4 grasses have evolved a more efficient way to fix carbon dioxide that minimizes water loss by using a different biochemical pathway that allows them to keep their stomata closed more often, particularly under high light and temperature conditions.

This distinction emphasizes the adaptability of C4 grasses to hotter and drier environments, granting them better water use efficiency and resilience compared to C3 grasses.