Vascular and Nonvascular Plants

Plants primarily contain three organ systems, compared to eleven in vertebrate animals. One of these systems is the vascular system, which consists of specialized tissues for transporting minerals, water, and nutrients throughout the plant.

The existence of this circulation system means that vascular plants can evolve to larger sizes than non-vascular plants. Non-vascular plants are limited to smaller sizes, since their tissues must transport water and nutrients from cell to cell. Non-vascular plants are more primitively and simply organized, and do not produce seeds or flowers.

The individual cells of phloem are connected from one end to another, just as the sections of a pipe might be. As the plant matures and grows, new vascular tissue differentiates in the growing tips of the plant. The new tissue is formed alongside the existing vascular tissue, maintaining its role throughout the plant.

Sparknotes offers explanations of the structure of xylem and phloem "pipes."

The vascular tissue in plants is arranged in long, discrete strands called vascular bundles. These bundles include both xylem and phloem, as well as supporting and protective cells. In stems and roots, the xylem typically lies closer to the interior of the stem with phloem towards the exterior of the stem.

Between the xylem and phloem is a meristematic tissue called the vascular cambium. This tissue divides into those cells that will be become additional xylem and phloem tissue. This growth increases the thickness of the plant, rather than its length.

As long as the vascular cambium continues to produce new cells, the plant will continue to grow stouter. In trees and other plants that produce wood, the vascular cambium allows the expansion of vascular tissue that produces woody growth.

Image credit: Kristen Fowler, Vascular Bundle, Pineapple Leaf (accessed June 4, 2007)
This work is licensed under a Creative Commons Attribution-Noncommercial 2.0 License.

Non-vascular plants include the mosses, liverworts, and hornworts, as well as those land plants without a vascular system.

Nonvascular plants do not have a xylem or phloem, roots, stems, or leaves. Because these plants lack water-conducting tissues, they fail to achieve the structural complexity and size of most vascular plants and have evolved in habitats which allow their survival and reproduction.

For more information on vascular and non-vascular plants and to see examples and images of each, please visit Mike Farrabee's Online Biology Book at Estrella Mountain College.

Image credit: C. Wood, Snake Liverwort, Carmanah Valley, Vancouver Island (accessed June 4, 2007)
This work is licensed under a Creative Commons Attribution-Noncommercial-NoDerivatives 2.0 License.

Vascular Plants

The vascular plants (found within the kingdom Plantae) include higher order plants that have specialized tissues for conducting water. Vascular plants include the ferns, horsetails, conifers, cycads, ginkgo, and flowering plants.

Vascular tissue is a complex tissue system found among vascular plants which includes a food and water 'transportation' system. The primary structures of vascular tissue are the xylem, or water conducting system, and the phloem, or nutrient conducting system. These two tissues work together to transport fluid and nutrients within the plant.

All the vascular tissues within a particular plant together comprise the vascular tissue system of that specific plant. The cells in differentiated vascular tissue are typically long and slender. Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form and structures resemble 'pipes.'