Eustele

Eustele refers to a specific arrangement of vascular tissues in the stems of plants. This pattern is characteristic of seed plants, including gymnosperms and angiosperms. In a eustele, the vascular bundles are discrete and arranged in a ring, separating the pith (the central core) from the cortex (the region between the vascular bundles and the epidermis). Each vascular bundle contains xylem, responsible for water transport, and phloem, responsible for sugar transport. The xylem is typically located towards the center of the stem, while the phloem is positioned towards the outside. Between the xylem and phloem, there is often cambium, a layer of actively dividing cells that allows for secondary growth, leading to an increase in stem diameter. This ring-like arrangement of vascular bundles is a significant evolutionary development, providing a more efficient and organized system for transporting water and nutrients throughout the plant compared to simpler arrangements found in some non-seed plants. The presence of a eustele is a key feature used in plant anatomy and classification.