Xylems are vascular cells that transport water from the root of the plant through its stem and up to the outer tips of its leaves. Xylems travel through the vascular bundles of the cell stem and the smaller bundled veins of its leaves. Xylems provide a counter-force to gravity by increasing the surface tension between water molecules and internal plant tissue.
Phloem transport nutrients and minerals between the stem, leaves and root of the plant. They transport sap and other sugars from the site of photosynthesis to the parts of the plant that use those sugars for energy.
The xylem of a vascular bundle lies towards the centre and is composed of vessels or tracheae, tracheids, wood fibres and a patch of xylem or wood parenchyma. The xylem elements, i.e., vessels and tracheids, aid in conduction of water and mineral salts from the roots to the leaves, whereas wood or xylem parenchyma are living tissues, and aid in the storage.
Usually in stems, phloem is found away from the centre of the axis towards the periphery and consists of sieve tubes or sieve cells only, or sieve tubes and companion cells only and phloem parenchyma. Phloem serves for translocation of prepared carbohydrates from leaves to the storage tissue and other growing regions.
xylem vessels are made of dead xylem cells. the water from the soil is absorbed into the roots through osmosis and is transported to the parts of the plant through the xylem vessels.(The water is needed for photosynthesis and other processes in the plant).
the phloem vessels are responsible for the transport of nutrients and food to the parts of the plant. nutrients from the soil and the food producuced by photosynthesis in a plant is transported to its storing place. some glucose that is produced is stored in the leaf but most is transported to the roots and stem etc.. for example, carrots and celery are very fiborous as the glucose (from photosynthesis) is transported to them and is stored as starch.