What do sporophytes produce

The cycle then begins anew. The spores of seedless plants are surrounded by thick cell walls containing a tough polymer known as sporopollenin. This complex substance is characterized by long chains of organic molecules related to fatty acids and carotenoids: hence the yellow color of most pollen.

Sporopollenin is unusually resistant to chemical and biological degradation. In seed plants, which use pollen to transfer the male sperm to the female egg, the toughness of sporopollenin explains the existence of well-preserved pollen fossils. Sporopollenin was once thought to be an innovation of land plants; however, the green algae, Coleochaetes, also forms spores that contain sporopollenin.

Gametangia singular, gametangium are organs observed on multicellular haploid gametophytes. In the gametangia, precursor cells give rise to gametes by mitosis. The male gametangium antheridium releases sperm. Many seedless plants produce sperm equipped with flagella that enable them to swim in a moist environment to the archegonia: the female gametangium.

The embryo develops inside the archegonium as the sporophyte. Some of them grow exclusively in dark, damp environments in order to provide moisture. Find out more about them here Read More.

Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum. Bryophytes Bryophytes nonvascular plants are a plant group characterized by lacking vascular tissues. Related Articles No related articles found See all Related Topics. All three zones are in the first centimeter or so of the root tip. Modified roots : Many vegetables are modified roots, such as radishes and carrots, which store energy in the form of starches and sugars.

The vascular tissue in the root is arranged in the inner portion of the root, which is called the vascular cylinder. A layer of cells, known as the endodermis, separates the vascular tissue from the ground tissue in the outer portion of the root. A waxy substance called suberin is present on the walls of the endodermal cells. This waxy region, known as the Casparian strip, forces water and solutes to cross the plasma membranes of endodermal cells instead of slipping between the cells.

This ensures that only materials required by the root pass through the endodermis, while toxic substances and pathogens are generally excluded. In dicot roots, the xylem and phloem of the stele are arranged alternately in an X shape, whereas in monocot roots, the vascular tissue is arranged in a ring around the pith.

Root structures may be modified for specific purposes. For example, some roots are bulbous and store starch. Aerial roots and prop roots are two forms of aboveground roots that provide additional support to anchor the plant. Tap roots, such as carrots, turnips, and beets, are examples of roots that are modified for food storage.

Ferns, club mosses, horsetails, and whisk ferns are seedless vascular plants that reproduce with spores and are found in moist environments. Water is required for fertilization of seedless vascular plants; most favor a moist environment. Modern-day seedless tracheophytes include lycophytes and monilophytes. The club mosses, or phylum Lycopodiophyta, are the earliest group of seedless vascular plants. They dominated the landscape of the Carboniferous, growing into tall trees and forming large swamp forests.

The phylum Lycopodiophyta consists of close to 1, species, including the quillworts Isoetales , the club mosses Lycopodiales , and spike mosses Selaginellales , none of which are true mosses or bryophytes.

Lycophytes follow the pattern of alternation of generations seen in the bryophytes, except that the sporophyte is the major stage of the life cycle. The gametophytes do not depend on the sporophyte for nutrients. Some gametophytes develop underground and form mycorrhizal associations with fungi. In club mosses, the sporophyte gives rise to sporophylls arranged in strobili, cone-like structures that give the class its name.

Lycophytes can be homosporous or heterosporous. Strobili of club mosses : In some club mosses such as Lycopodium clavatum , sporangia are arranged in clusters called strobili.

Horsetails, whisk ferns, and ferns belong to the phylum Monilophyta, with horsetails placed in the Class Equisetopsida. The single extant genus Equisetum is the survivor of a large group of plants, which produced large trees, shrubs, and vines in the swamp forests in the Carboniferous. The plants are usually found in damp environments and marshes. Leaves and branches come out as whorls from the evenly-spaced joints.

The needle-shaped leaves do not contribute greatly to photosynthesis, the majority of which takes place in the green stem. Leaves of a horsetail : The whorls of green structures at the joints are actually stems. The leaves are barely noticeable as brown rings just above each joint. Horsetails were once used as scrubbing brushes and so were called scouring rushes. Silica collects in the epidermal cells, contributing to the stiffness of horsetail plants.

Underground stems known as rhizomes anchor the plants to the ground. Modern-day horsetails are homosporous and produce bisexual gametophytes. While most ferns form large leaves and branching roots, the whisk ferns, Class Psilotopsida, lack both roots and leaves, which were probably lost by reduction. Photosynthesis takes place in their green stems; small yellow knobs form at the tip of the branch stem and contain the sporangia.

Whisk ferns were considered an early pterophytes. However, recent comparative DNA analysis suggests that this group may have lost both leaves and roots through evolution and is more closely related to ferns. With their large fronds, ferns are the most-readily recognizable seedless vascular plants. More than 20, species of ferns live in environments ranging from tropics to temperate forests. Although some species survive in dry environments, most ferns are restricted to moist, shaded places.

Ferns made their appearance in the fossil record during the Devonian period and expanded during the Carboniferous. The dominant stage of the life cycle of a fern is the sporophyte, which typically consists of large compound leaves called fronds. Fronds fulfill a double role; they are photosynthetic organs that also carry reproductive structure. The stem may be buried underground as a rhizome from which adventitious roots grow to absorb water and nutrients from the soil, or they may grow above ground as a trunk in tree ferns.

Adventitious organs are those that grow in unusual places, such as roots growing from the side of a stem. Most ferns produce the same type of spores and are, therefore, homosporous. The diploid sporophyte is the most conspicuous stage of the life cycle.

On the underside of its mature fronds, sori singular, sorus form as small clusters where sporangia develop. Sporangia in a sorus produce spores by meiosis and release them into the air. Those that land on a suitable substrate germinate and form a heart-shaped gametophyte, which is attached to the ground by thin filamentous rhizoids. The inconspicuous gametophyte harbors both sex gametangia.

Flagellated sperm are released and swim on a wet surface to where the egg is fertilized. The newly-formed zygote grows into a sporophyte that emerges from the gametophyte, growing by mitosis into the next generation sporophyte. Sori on a fern frond : Sori appear as small bumps on the underside of a fern frond. Seedless vascular plants provide many benefits to life in ecosystems, including food and shelter and, to humans, fuel and medicine. Mosses and liverworts are often the first macroscopic organisms to colonize an area, both in a primary succession where bare land is settled for the first time by living organisms or in a secondary succession where soil remains intact after a catastrophic event wipes out many existing species.

Their spores are carried by the wind, birds, or insects. Once mosses and liverworts are established, they provide food and shelter for other species. In a hostile environment, such as the tundra where the soil is frozen, bryophytes grow well because they do not have roots and can dry and rehydrate rapidly once water is again available.

Mosses are at the base of the food chain in the tundra biome. Many species, from small insects to musk oxen and reindeer, depend on mosses for food. In turn, predators feed on the herbivores, which are the primary consumers.

Some reports indicate that bryophytes make the soil more amenable to colonization by other plants.