Explain how water is carried by transpiration stream, including the structure of xylem vessels, transportational pull, cohesion, adhesion, and evaporation

Some of the light energy absorbed by leaves changes into heat, converting water in the spongy mesophyll into vapor
This vapor diffuses out of the stomata and is evaporated, creating a negative pressure gradient in the leaf
New water is drawn from the xylem (mass flow), which is replaced by water from the roots (enters from soil via osmosis)
The flow of water through the xylem from the roots to the leaf is called the transpiration stream
Water rises through xylem vessels because of two qualities:
Cohesion:  Water molecules are weakly attracted to each other via hydrogen bonds
Adhesion:  Water molecules form hydrogen bonds with the xylem cell wall
These properties create a suction effect (or transpiration pull) in the xylem
The xylem has a specialized structure to facilitate transpiration:
The inner lining is composed of dead cells that have fused to create a continuous tube
These cells lack a cell membrane, allowing water to enter the xylem freely
The outer layer is perforated (contains pores), allowing water to move out of the xylem into the leaves
The outer cell wall contains annular ligin rings which strengthens the xylem against the tension created by the transpiration stream