noun, plural: xylems
In plants, the different types of tissues include the meristematic tissues, the permanent tissues, and the reproductive tissues. The permanent tissues are further classified into fundamental tissues and the complex permanent tissues. The complex permanent tissues include the vascular tissues, particularly, xylem and phloem.
Xylem is the vascular tissue responsible for the conduction of water and nutrients from the roots up to the shoots and leaves, especially of terrestrial plants. Xylem is comprised of the xylem parenchyma, xylem fiber (or sclerenchyma), tracheids, and vessels. It is the primary component of wood in plants.
The mode of transport is by passive transport. For taller plants, though, the capillary action is coupled by transpiration, which is the loss of water by evaporation. The loss of water through transpiration leads to a high surface tension, which in turn, results in a negative pressure in the xylem. Consequently, the water from the roots is lifted to as high as several meters from the ground towards the apical parts of the plant.
Word origin: Greek xylon ("wood")