Root hairs are the small projections that grow at the ends of the roots. This is where most of the water absorption happens. The root hairs collect the water and mineral nutrients that are present in the soil and pass this along through the roots to the rest of the plants.
At the end of each root are the root caps. They cover and protect the growing tips of the roots. Root caps are also called calyptra. They have cells called statocytes that are believed to help the root perceive gravity, allowing it to grow downwards (with gravity) or upwards (against gravity).