Describe the differentiating traits that the three varieties of bryophytesIdentify the brand-new traits that first appear in seedless vascular plantsDescribe the major classes that seedless vascular plants

An incredible variety of seedless tree populates the terrestrial landscape. Mosses grow on tree trunks, and horsetails (

) display screen their jointed stems and spindly pipeline on the forest floor. Yet, seedless plants represent just a small portion of the tree in our environment. 3 hundred million years ago, seedless plants dominated the landscape and also grew in the enormous swampy forests of the Carboniferous period. Their decomposing body created big deposits of coal that we mine today.

You are watching: Which is the most diverse group of seedless vascular plants?

Figure 2: (a) A 1904 illustration of liverworts reflects the range of their forms. (b) A liverwort, Lunularia cruciata, displays its lobate, flat thallus. The biology in the photo is in the gametophyte stage.

HornwortsThe hornworts (Anthocerotophyta) have colonized a selection of habitats on land, although they space never much from a resource of moisture. There are about 100 described types of hornworts. The leading phase that the life bicycle of hornworts is the short, blue-green gametophyte. The sporophyte is the specifying characteristic of the group. That is a long and also narrow pipe-like structure that emerges from the parental gametophyte and also maintains development throughout the life that the plant (


Figure 4: This green feathery moss has actually reddish-brown sporophytes growing upward. (credit: “Lordgrunt”/Wikimedia Commons)Vascular Plants

The vascular plants are the dominant and most conspicuous group of land plants. There are around 275,000 types of vascular plants, which represent much more than 90 percent of earth vegetation. Number of evolutionary innovations define their success and their spread to so plenty of habitats.

Vascular Tissue: Xylem and Phloem

The first fossils that display the presence of vascular tissue space dated to the Silurian period, around 430 million years ago. The simplest arrangement of conductive cells shows a sample of xylem at the facility surrounded by phloem. Xylem is the tissue responsible because that long-distance deliver of water and minerals, the transfer of water-soluble growth determinants from the offal of synthetic to the target organs, and storage of water and also nutrients.

A second form of vascular organization is phloem, i beg your pardon transports sugars, proteins, and other solutes with the plant. Phloem cells are separated into sieve elements, or conducting cells, and also supportive tissue. Together, xylem and also phloem tissues form the vascular system of plants.

Roots: support for the Plant

Roots are not well maintained in the fossil record; nevertheless, it seems that castle did show up later in evolution than vascular tissue. The advance of comprehensive network the roots stood for a significant new feature of vascular plants. Slim rhizoids fastened the bryophytes to the substrate. Their quite flimsy filaments did not provide a strong anchor because that the plant; neither did they absorb water and nutrients. In contrast, roots, through their prominent vascular tissue system, deliver water and minerals indigenous the floor to the remainder of the plant. The comprehensive network the roots that penetrates deep in the ground come reach sources of water also stabilizes trees by acting together ballast and an anchor. The majority of roots develop a symbiotic relationship with fungi, creating mycorrhizae. In the mycorrhizae, fungal hyphae grow approximately the root and within the root about the cells, and also in some instances within the cells. This benefits the tree by significantly increasing the surface area for absorption.

Leaves, Sporophylls, and also Strobili

A 3rd adaptation clues seedless vascular plants. Accompanying the importance of the sporophyte and also the breakthrough of vascular tissue, the illustration of true leaves improved photosynthetic efficiency. Leaves capture an ext sunlight v their raised surface area.

In addition to photosynthesis, pipeline play another role in the life that the plants. Pinecones, mature fronds that ferns, and flowers room all sporophylls—leaves the were amendment structurally come bear sporangia. Strobili space structures the contain the sporangia. They are influential in conifers and are known commonly as cones: for example, the pine tree cones of jaw trees.

Seedless Vascular Plants

By the late Devonian duration (385 million year ago), plants had evolved vascular tissue, well-defined leaves, and also root systems. Through these advantages, plants enhanced in height and also size. During the Carboniferous period (359–299 million years ago), swamp woodlands of club mosses and horsetails, v some specimens reaching more than 30 meters tall, covered most of the land. These forests gave climb to the extensive coal shop that provided the Carboniferous the name. In seedless vascular plants, the sporophyte ended up being the leading phase the the lifecycle.

Water is still required for fertilization that seedless vascular plants, and also most donate a moist environment. Contemporary seedless vascular plants encompass club mosses, horsetails, ferns, and whisk ferns.

Club Mosses

The club mosses, or Lycophyta, are the earliest team of seedless vascular plants. They conquered the landscape of the Carboniferous period, farming into tall trees and forming large swamp forests. Today’s society mosses room diminutive, evergreen tree consisting that a stem (which might be branched) and little leaves referred to as microphylls (

). The department Lycophyta consists of close come 1,000 species, consisting of quillworts (Isoetales), society mosses (Lycopodiales), and also spike mosses (Selaginellales): none of i beg your pardon is a true moss.

See more: 2005 Ford F150 Ac Recharge Port, Ford F150: How To Recharge Air Conditioning

Figure 6: Horsetails thrive in a marsh. (credit: Myriam Feldman)

The stem the a horsetail is defined by the visibility of joints, or nodes: therefore the name Arthrophyta, which way “jointed plant”. Leaves and also branches come out as whorls indigenous the evenly spaced rings. The needle-shaped leaves perform not contribute greatly to photosynthesis, the majority of i m sorry takes ar in the environment-friendly stem (


Figure 8: some specimens that this quick tree-fern species can grow an extremely tall. (credit: Adrian Pingstone)
Figure 9: This chart reflects the geological time scale, beginning with the Pre-Archean eon 3800 million years ago and ending with the Quaternary duration in existing time. (credit: change of work by USGS)