"The source, white and wet, /The most sensitive, hidden" What does the word ‘source’ refer to here? How does the poet describe the root and its function?

The poet has vividly described the root. His scientific outlook and poetic imagination are mingled in his observation of the root. He considers the root to be the anchor of the tree that stands firmly on the ground. The root is actually the strength of the tree. It is the source of life. This life-supporting source is white and wet. It is white because it has never been exposed to sunlight but is hidden inside the earth. It is wet because it is full of water and other nutrients. The poet calls the root the most sensitive thereby associating human quality to the tree.