Types of xylem tissue

Xylem tissue can be classified into two main types based on its development:

1. Primary xylem: This is the first xylem to form and is part of the primary plant body. It develops from the procambium. Primary xylem is further divided into:

   • Protoxylem: The first-formed primary xylem. It typically has annular or helical secondary wall thickenings, allowing it to stretch as the stem elongates.
   • Metaxylem: The later-formed primary xylem. It has more developed secondary wall thickenings, such as scalariform, reticulate, or pitted patterns.

2. Secondary xylem: This is the xylem that forms from the vascular cambium during secondary growth. It is found in woody plants and is responsible for the increase in stem and root diameter. Secondary xylem consists mainly of tracheids, vessel elements, xylem parenchyma, and xylem fibers.