Definition - What does Xylem mean?
Xylem is one of two pathways (phloem is the other one) in a plant's vascular system that transports water and nutrients, through a process called transpiration.
During transpiration, the xylem and phloem help transport dissolved minerals throughout a plant from its roots into its branches and stems.
Some nutrients, such as boron, calcium, copper, iron, manganese, molybdenum, and zinc, can only move upwards in the xylem. Others can flow both up, down, and throughout the xylem. Such nutrients include the macro-nutrients: magnesium, nitrogen, phosphorous, potassium, and sulfur.
Hydrolife explains Xylem
Xylem is a part of a vascular plant's anatomy. Along with the phloem, they make up the 'nutrient highway' in the plant in which nutrients travel. Excess water transported by the xylem is “exhaled” by the plant through its stomata. On cannabis plants, the stomata is on the underside of the leaves.
Xylem sap can sometimes ooze out of the stomata (appearing like dew but formed at night when stomata are closed) in cannabis plants by a process known as “guttation”.
Cannabis growers should be cautioned about using pesticides on their crops as any pesticide that the plant has absorbed may weep out in the xylem sap.
This same xylem sap can cause burning of cannabis leaves if nutrient levels are too high. This will be visible on the leaf surface and appear like the efflorescence of winter salts on brick walls and walkways.