Late * primary xylem. The metaxylem completes its elongation after the organ has ceased longitudinal growth and therefore its tracheary elements are not destroyed. Like the * protoxylem , the metaxylem is composed mostly of tracheary elements and parenchyma cells, but sclerenchyma fibres may also be present. The vessels or tracheids of the metaxylem, however, are generally wider and more numerous than those of the protoxylem and have pitted secondary cell walls. In plants not exhibiting secondary growth at maturity, the metaxylem is the only water-conducting vascular tissue. Compare metaphloem. |
