H bonds of water, hydrophilic walls of xylem and small diameter of xylem aid in the movement of water up the tube. This pull decreases water pressure in the xylem causing the roots to take water from the soil. Turgid guard cells open the stomata, while flaccid cells close them. Phloem carries sucrose, minerals, amino acids, and hormones. Organ that consumes or stores the sugar.
Flow is always from the source to the sink.
Phloem is loads by active transport.