vascular bundle

Vascular bundles are tissues specialized on the transport of water, nutrients, and assimilate. They typically consist of elongated cells which constitute a tubular system connecting roots and leaves. Xylem and phloem are the most important tissues. In the xylem, water is transported from the roots to the leaves. It mainly consists of dead lignified cells (vessel elements and tracheids, respectively). The phloem transports assimilate from the leaves to cells or storage organs. It consists mainly of living not-lignified cells (e. g. sieve tube members). Vascular bundles, e. g. in the leaf veins, are regularly associated with sclerenchyma, often as sclerenchymatous sheaths or sclerenchymatous strands.