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| Easy Q&A Review of Pteridophytes
1. What are the main representatives of the pteridophytes? Is this plant group cryptogamic or phanerogamic? The better known pteridophytes are the ferns and the maidenhairs, from the filicinae (filicopsida) group, and the selaginellas, mosslike plants from the lycopodineae group (lycopsida). Pteridophytes are cryptogamic plants, i.e., they are flowerless and seedless. Image Diversity: pteridophytes ferns maidenhairs selaginellas 2. How different are pteridophytes from bryophytes regarding substance transport? Pteridophytes are tracheophyte (vascular) plants, i.e., they have tissues specialized in conduction of water and nutrients. Bryophytes are nonvascular plants. In pteridophytes therefore the substance transport is done through vessels and in bryophytes that transport occurs by diffusion. Image Diversity: vascular plants 3. Why are pteridophytes better adapted to dry land than bryophytes? Were pteridophytes always less abundant than phanerogamic plants? Although bryophytes and pteridophytes have water-dependant gametes for fecundation the emergence of conductive vessels in this last group facilitated life in a terrestrial environment. The conductive vessels of the pteridophytes collect water from the moist soil and distribute it to the cells. Bryophytes do not have this option and they depend entirely on the water that reaches the aerial part of the plant and so they need to live in humid or rainy places. Before the ascension of the phanerogamic plants (plants that present seeds) the pteridophytes were the plants that predominated in the terrestrial environment. The large pteridophyte forests of the Carboniferous period (named after the pteridophytes) are responsible for the formation of coal deposits, mainly in Europe, Asia and North America; the Carboniferous period occurred between 290 and 360 million years ago and is part of the Paleozoic era. Image Diversity: Carboniferous forests 4. What is the evolutionary importance of pteridophytes? As the first tracheophytes, pteridophytes were also the first plants to extensively colonize the terrestrial environment forming forests. They also constituted an important source of food for terrestrial animals. By presenting conductive vessels they could be larger, a feature inherited from them by phanerogamic plants. 5. What are the main parts of ferns? Ferns are constituted by small roots that come downwards from the rhizome (stem, often horizontalized). The fronds also arise from the rhizome. On the back side of each leaf of the plant there are small dustlike dots called sori (singular, “sorus”, also known as “seeds”). Image Diversity: pteridophyte parts 6. What is the type of life cycle present in pteridophytes? Like all plants pteridophytes present diplobiontic (alternation of generations, or metagenesis) life cycle. Image Diversity: pteridophyte life cycle 7. Why are pteridophytes more common in humid places? Pteridophytes are more common in humid places because they depend on water for their gametes to fecundate one another. In humid environments their reproduction is more intense and they proliferate. 8. What is the structure of the adult fern within which cells undergoing meiosis can be found? In these plants meiosis takes place within structures called sorus (plural, sori), small dustlike brown dots lining the underside of fern leaves. The sori contain sporangia where reproductive cells undergo meiosis and where spores are produced. 9. What is the prothallus of pteridophytes? Prothallus is the pteridophyte gametophyte (the haploid individual that forms gametes). The gametophyte develops by mitosis from a spore. Image Diversity: prothallus 10. How are gametes formed in the pteridophyte life cycle, by mitosis or meiosis? What is the type of meiosis that occurs in pteridophytes? In pteridophytes gametes are made by mitosis from special cells of the gametophyte. As in all plants, in pteridophytes, meiosis is sporic, i.e., cells of the sporophyte undergo meiosis and generate spores that then by mitosis develop into the gametophyte. 11. What is the lasting form in pteridophytes, the gametophyte or the sporophyte? How can it be compared to bryophytes? The lasting form in pteridophytes is the diploid (2n) sporophyte (the fern itself, for example). In bryophytes the lasting form is the gametophyte (n). 12. What is xaxim? Most pteridophytes have subterraneous stems parallel to the substrate called rhizomes. Xaxim is a type of pteridophyte with an aerial stem generally perpendicular to the soil and from which hundreds of roots arise to absorb water from the environment. The xaxim stem is used to make flower pots and other plant supports for gardening (also popularly known as xaxim). Image Diversity: xaxim |