1. the first-formed primary xylem tissue in plant stems and roots, characterized by narrow vessels and tracheids
Usage: botanical

Examples

• The protoxylems develop before the metaxylems in the vascular bundles.
• Botanists examined the protoxylems under a microscope to study early plant development.
• The narrow vessels of the protoxylems are easily distinguished from later-formed xylem tissue.
• In young seedlings, the protoxylems provide the initial water transport system.
• The formation of protoxylems marks an important stage in plant vascular development.