What are bryophytes?

Bryophytes are a group of non-vascular plants that include mosses, liverworts, and hornworts. Unlike vascular plants (such as ferns, conifers, and flowering plants), they lack a well-developed system for transporting water and nutrients (vascular tissues like xylem and phloem). As a result, bryophytes rely on their environment for moisture and must live in humid, shaded areas to survive.

Bryophytes are primitive plants that appeared around 450 million years ago, making them some of the earliest land plants. They play a significant role in ecosystems by helping in soil formation, regulating water cycles, and providing habitats for small organisms.

Marchantia, a species in the genus of liverworts moss

Characteristics and differences from other plants

Bryophytes differ from vascular plants in several ways:

Lack of vascular tissues

While vascular plants have an internal system (xylem and phloem) to transport water and nutrients, bryophytes absorb water directly through their surfaces from the surrounding environment. This limits their size and makes them more dependent on moist habitats.

No true roots

Instead of roots, bryophytes have rhizoids, which are root-like structures that anchor them to the ground but do not play a significant role in nutrient absorption.

Dominant gametophyte stage

Bryophytes exhibit an alternation of generations, but in contrast to most vascular plants, the gametophyte stage (the phase that produces sex cells) is the dominant, visible form. In vascular plants, the sporophyte stage is dominant.

Water-dependent reproduction

Bryophytes have no pollen nor flowers but reproduce through spores and need water for fertilization. Their sperm must swim through water to reach the eggs and fertilize them to produce the spores, which explains their preference for moist environments.

Size and structure

Bryophytes are generally small, with simple structures. Mosses, for example, have a basic stem-and-leaf structure, whereas liverworts often have a flat, thalloid body.

The specificities of European bryophytes

Though bryophytes are widespread, their distribution and diversity can differ based on geography, climate, and local environments.

Europe is home to a diverse range of bryophytes, especially in its temperate and boreal regions. Western and Northern Europe, including the UK, Scandinavia, and parts of the Alps, have an abundance of mosses and liverworts. These regions provide moist, cool environments ideal for bryophyte growth. Many European bryophytes thrive in forested areas, peat bogs, and along streams. A significant part of Europe’s bryophyte diversity is found in mountainous regions where the cooler, damp conditions mimic the environments in which bryophytes flourish.

In the United States, bryophytes are also widespread, but the diversity and distribution patterns differ. The Pacific Northwest, with its rainforests and damp coastal areas, is a hotspot for bryophytes in North America. Unlike Europe, where bryophytes are concentrated in cooler climates, the United States shows greater diversity across a wider range of environments, from coastal rainforests to drier, warmer areas. Bryophyte communities in North America can sometimes be found in more xeric (dry) conditions compared to their European counterparts. Some species are common to both Europe and North America, however, bryophyte communities in North America might include more endemic species.