Roots are considered to be an important part of a plant. The primary sources for a plants growth are food, water and oxygen. Without water a plant will not be able to grow and it will die soon. Therefore, water is an essential part for the growth of a plant.
Plant cells are important to support the plant (they become turgid when they take in water. Other cells have various functions: root hair cells are adapted to take water and nutrients from soil, xylem cells form tubes to transport water and phloem cells form special tubes for sugar transport.
in a plant if you look carefully and debark a tree you will see llines going up theese are cells. the roots collect water from the ground gives it to the cells and the cells take the water to the rest of a plant.
take water and minerals from roots to the leaves and take food substances from leaf to rest of the plant. and if its a non-photosynthetic plant then food from its environment/special organ to rest of the plant.
as much water as the plant needs. each plant is different. you will need to monitor the plant daily and see if the leaves are beginning to wilt or if something looks wrong. do not try to overwater the plant, though, because too much water is not good for the plant.
Soil and water help a plant grow because when the roots take up the water from the soil,some of it's minerals have dissolved in the water giving the plant nutrients. Water also helps the plants make food using the process photosynthesis.
The process of water moving from a plant to the cloud and the other way around is described in the water cycle. Plants take up water from the soil through its roots after rainfall and gives it back to the atmosphere through evaporation from the leaves.