What is made in the antheridium

Sperm are produced in structures called antheridia sing. As in protists and fungi, spores of plants are produced in sporangia sing. A dependent sporophyte is a sporophyte that is small and grows attached to the gametophyte. It obtains nutrients from the gametophyte. An independent sporophyte grows separately from the gametophyte. Similarly, a dependent gametophyte is small and grows attached to the sporophyte while an independent gametophyte grows separately from the sporophyte.

The evolutionary trend in plants has been from plants with a dominant gametophyte and reduced, dependent sporophyte ex. Mosses to plants with a dominant, independent sporophyte and a reduced, dependent gametophyte ex. Seed plants. Eudicots Bryophytes Phylum: Bryophyta Mosses Observe different kinds of moss on display and note the body form of the gametophyte. Observe live Marchantia a liverwort. Do the plants contain gemma cups? What is the function of gemma cups? Observe a live horsetail if available.

Find the a strobilus. What reproductive structures are contained within the strobilus? Members of this phylum have horizontal stems, upright stems, and small, spike-shaped leaves called microphylls.

Observe a specimen of live club mosses such as Lycopodium. Find rhizomes. Identify microphylls. Do the specimens have any strobili? Be sure to look up these words if you do not understand them. Observe a specimen of a spike moss such as Selaginella. Note the structure of the microphylls. Skip to main content.

Module 4: Seedless Plants. Search for:. Reading: Seedless Plants Introduction Plants kingdom Plantae are autotrophs ; they make their own organic nutrients. Some evidence that suggests that plants evolved from the green algae is: they both use chlorophyll a, chlorophyll b, and carotenoid pigments during photosynthesis. These traits occur in plants but not charophyceans.

Some evolved independently in other algae. Apical meristems Alternation of generations Spores with protective walls Spores produced in sporangia Gametes are produced in multicellular structures called gametangia; Antheridia produce sperm; Archegonia produce eggs Multicellular dependent embryos Many have a cuticle that waterproofs and offers some protection Alternation of Generations The basic alternation of generations life cycle is illustrated below.

Figure 1. Moss growing on a rock. Figure 2. In some bryophytes a mature antheridium will hold free sperm, but more commonly that's not the case, Rather, each sperm is still held within the cell in which it formed. In such a case, when an antheridium opens, those sperm-containing cells are released and it is only at some stage after release from the antheridium that the single sperm, within each such cell, is liberated.

Such liberation may take place shortly after the opening of the antheridium or as long as 15 minutes later, depending on species. In the following, the expression "sperm mass" will mean either a mass of free sperm or a mass of sperm-containing cells, when it's not essential to distinguish the two.

When a mature antheridium is moistened the cells at the apex absorb water, swell and finally burst or open in some way. The sperm mass inside a mature antheridium is under pressure. So, once an antheridium has opened, the sperm mass is forced out.

In some bryophytes the force is enough to shoot the sperm mass into the air, allowing dispersal over a relatively wide area. However, in most cases the sperm mass simply oozes into the area around the antheridium and further dispersal is by some other means. While the entire sperm mass may sometimes be released during the forceful extrusion, release is more often a two-stage process.

Typically a large percentage of the spore mass is quickly forced out by the built-up internal pressure, but a proportion remains within the antheridium and exits more slowly, over many minutes. The summary in the previous paragraph is enough to give you a quick grasp of the broad features of the process, but there is variation in the finer detail between species.

The sperm-to-egg process has been thoroughly studied in a relatively small number of bryophytes. Thus, the examples given on that page may not explain the processes in all bryophytes, but you will at least see some of the variations that are known to occur. Once an egg has been fertilized the development of the sporophyte begins. The fertilized egg elongates and after a few cell divisions begins to differentiate.

The lower portion usually becomes a foot that penetrates the gametophyte and anchors the embryonic sporophyte to the gametophyte. The upper will develop into the spore-bearing capsule and also the supporting stalk or seta , in species in which the mature capsule is stalked. The sporophytes are at least partially dependent on the gametophyte for nutrients.

Transfer cells develop at the sporophyte-gametophyte boundary in the majority of bryophytes, but not all. These cells are specialized cells that allow efficient transfer of nutrients from the gametophyte to the sporophyte.

In the bryophytes where they do occur they may be formed on the gametophyte, the sporophyte or both. So, combined with the possibility of no transfer cells, there are four possibilities. All hornworts have transfer cells and they form only on the gametophyte.

Three of the four possibilities occur in mosses. In the majority of moss genera the transfer cells are found on both the gametophyte and the sporophyte, though they are absent in Sphagnum and in a small number of moss genera they are found only on the sporophyte. A common example of the last is the genus Polytrichum and its close relatives. In the liverworts all four possibilities occur. The leafy liverworts have transfer cells only on the sporophytes.

In the complex thallose liverworts the transfer cells are found on both sporophyte and gametophyte. In the simple thalloid liverworts there are examples of all four possibilities. The gametophyte-sporophyte junction often has a convoluted, maze-like form. This gives a larger surface area and hence more transfer cells than would a simple, smooth boundary and so increases the rate at which nutrients can flow to the sporophyte.

After fertilization, the archegonium becomes modified into a protective sheath around the young sporophyte. There are significant differences, in both structure and development, between hornwort, liverwort and moss sporophytes.

In mosses the archegonia are typically formed in groups. In many cases once one archegonium in such a group has been fertilized the others lose the ability to be fertilized. This appears to be caused by an inhibitory hormone released from a fertilized archegonium. In such circumstances only one sporophyte can develop from that archegonial group.

However, in some circumstances more than one sporophyte may develop from an archegonial group.