CBSE Class 10 Answered

Transpiration and root pressure are the 2 main forces responsible for transporting water in plants.

At night, transpiration is low or zero. So it has minimal or no role in upward transportation of water. Without transpiration to carry the ions up the stem, they accumulate in the root xylem and lower the water potential. Water then diffuses from the soil into the root xylem due to osmosis. Root pressure is caused by this accumulation of water in the xylem pushing on the rigid cells. Root pressure provides a force, which pushes water up the stem. Thus root pressure can transport water and dissolved mineral nutrients from roots through the xylem to the tops of relatively short plants when transpiration is low or zero.