Nonvascular Plants

Nonvascular plants are plants that do not have any special internal pipelines or channels to carry water and nutrients. Instead, nonvascular plants absorb water and minerals directly through their leaflike scales. Nonvascular plants are usually found growing close to the ground in damp, moist places.

Nonvascular plants are made up of mosses, liverworts, and hornworts—all of which belong to the subdivision of plants called Bryophyta or bryophytes. They are described as nonvascular because they do not have an internal transport or circulatory system as do other plants. Bryophytes are also nonflowering plants, meaning that they reproduce without growing flowers. Lacking a system to move food and minerals, these plants are unable to grow very tall since they depend on direct contact with moisture. Bryophytes lack true leaves and do not have roots, using rhizoids instead. Rhizoids are slender, rootlike hairs that both anchor and absorb like roots.

After rhizoids perform this initial absorption, movement throughout the plant takes place by the processes of diffusion and active transport. Diffusion is the distribution of a substance away from an area where it is highly concentrated. In this way, water and nutrients move from cells that are full to cells that are empty. Diffusion uses no energy. Active transport, however, does require a plant to use energy. It is used when a plant needs to achieve the opposite of diffusion and must try to concentrate a substance in one place. A plant carries out active transport by using carrier protein molecules. These molecules actually carry the needed substance from one side of a cell membrane to the other. Because of this essentially primitive means of obtaining and moving water and nutrients, a humid, moist environment is essential to nonvascular plants.

[See alsoPlant Anatomy; Plants ]