Dictionary > Protoxylem


The first xylem to develop from the procambium, and characterized by narrow tracheary elements with annular, spiral or reticular thickenings
The xylem is the vascular tissue that is responsible for the conduction of water and nutrients from the roots up to the shoots and leaves. In contrast, the phloem is the other vascular tissue and is responsible for the translocation of metabolic products in various parts of the plant. The xylem may be categorized as primary xylem or secondary xylem. These two types of xylems are distinguished based on their origin. The primary xylem is produced from primary growth. The procambium gives rise to the primary xylem.
The primary xylem may be differentiated into two main parts: protoxylem and metaxylem. Both protoxylem and metaxylem contain tracheids, vessels, and parenchyma. They are produced from the procambium. Nevertheless, the protoxylem is the first xylem that develops (thus, the name). It consists of narrow vessels. The vessels are formed of cells that are relatively smaller than those of metaxylem. Nevertheless, the protoxylem has more parenchyma cells than metaxylem. In young plants, the protoxylem in stems has very little secondary wall material. In the stem, it is arranged towards the center whereas in the root, it is towards the periphery.
In a young stem, the protoxylem consists of tracheary element with annular or spiral thickenings, hence, capable of stretching or elongating (for stem growth). As the stem gets older, the stem stops elongating and the tracheary elements become more filled in.
Word origin: Greek prôtos (“first”) + xylem, from Greek xúlon (“wood”)
See also:

You will also like...

Sugar Homeostasis
Sugar Homeostasis

The blood sugar level is regulated by two hormones. The mechanism behind this type of negative feedback control is descr..

A chart depicting Mendel's Law of Dominance
Mendel’s Law & Mendelian Genetics

One of Mendel’s law of inheritance is the “law of dominance”. Read this tutorial to know more about this form of i..

Lotic community of algal species
Lotic Communities & Algae

Lotic communities have conditions that are rather harsh for typical plants. Thus, the diversity of plant species in loti..

Water Cycle
The Water Cycle

The water cycle (also referred to as the hydrological cycle) is a system of continuous transfer of water from the air, s..

Freshwater Ecology
Freshwater Ecology

Freshwater ecology focuses on the relations of aquatic organisms to their freshwater habitats. There are two forms of co..

Pink Lotus plant on a pond
Freshwater Lentic Communities & Animals

This tutorial looks at some of the communities in freshwater lentic habitats. For instance, symbiosis occurs in a commun..