Summarizing Seedless Vascular Plants

Summary

Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. With the development of the vascular system, there appeared leaves to act as large photosynthetic organs, and roots to access water from the ground. Small uncomplicated leaves are microphylls. Large leaves with vein patterns are megaphylls. Modified leaves that bear sporangia are sporophylls. Some sporophylls are arranged in cone structures called strobili.

The seedless vascular plants include club mosses, which are the most primitive; whisk ferns, which lost leaves and roots by reductive evolution; and horsetails and ferns. Ferns are the most advanced group of seedless vascular plants. They are distinguished by large leaves called fronds and small sporangia-containing structures called sori, which are found on the underside of the fronds.

Mosses play an essential role in the balance of the ecosystems; they are pioneering species that colonize bare or devastated environments and make it possible for a succession to occur. They contribute to the enrichment of the soil and provide shelter and nutrients for animals in hostile environments. Mosses and ferns can be used as fuels and serve culinary, medical, and decorative purposes.

Glossary

adventitious

describes an organ that grows in an unusual place, such as a roots growing from the side of a stem

club mosses

earliest group of seedless vascular plants

fern

seedless vascular plant that produces large fronds; the most advanced group of seedless vascular plants

horsetail

seedless vascular plant characterized by joints

lignin

complex polymer impermeable to water

lycophyte

club moss

megaphyll

larger leaves with a pattern of branching veins

microphyll

small size and simple vascular system with a single unbranched vein

peat moss

Sphagnum

phloem

tissue responsible for transport of sugars, proteins, and other solutes

sporophyll

leaf modified structurally to bear sporangia

strobili

cone-like structures that contain the sporangia

tracheophyte

vascular plant

vein

bundle of vascular tissue made of xylem and phloem

whisk fern

seedless vascular plant that lost roots and leaves by reduction

xylem

tissue responsible for long-distance transport of water and nutrients