Measurements of the stem of a young tree showed that the diameter varied slightly. It decreased during the day and increased during the night.
Which statement explains these observations?
1 )
During the day, cohesion between water molecules and lignin in the walls of the xylem vessels pulls the walls of the vessels inwards.
During the day, the tension developed in a moving column of water molecules reduces the pressure inside the xylem vessels, so that their walls move inwards.
3 )
During the night, the adhesion of water molecules to the lignin in the walls of the xylem vessels pushes the walls of the vessels outwards.
4 )
During the night, the pressure of the column of water molecules adhering to one another increases and pushes the walls of the xylem vessels outwards.
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