DIVERSITY OF PTERIDOPHYTES B C D Fertilization G E F www.bupoyesiku.net ~ 1 ~ Department of Plant Science
Contents Topic: Diversity of Pteridophytes... 3 Objectives... 3 Reading ssignment... 3 Lecture... 3 Introduction... 4 Main Content... 4 Background of Pteridophytes... 4 Reproduction in Pteridophytes... 4 Vegetative reproduction... 4 sexual reproduction... 5 Sexual reproduction... 5 Classification of Pteridophytes... 6 Characteristics of Pteridophytes... 7 Diversity of Forms in Pteridophytes... 7 Habitats of Pteridophytes... 9 Ecology of Pteridophytes... 9 Economic uses of Pteridophytes... 9 Conclusion... 10 Summary... 10 References/Further readings/links... 10 Test Yourself Questions (TYQ)... 11 www.bupoyesiku.net ~ 2 ~ Department of Plant Science
Topic: Diversity of Pteridophytes Objectives In this lecture we will learn the followings: Clear idea of the features that separate Pteridophytes from other plants Skills in identifying them in our environment Importance of the Pteridophytes Contributions to our lives Reading ssignment In addition to the discussion in this lecture you should read current textbooks in the library and visit: ilearn.bupoyesiku.net for the online lecture. Lecture In previous lecture we discussed about non-vascular green plant bryophytes. In our earlier lectures, you have learnt about the characteristics of the members of algae, lichen, fungi and monera. In our today s lecture, we are going to be discussing the most advanced member of the spore plants, the Pteridophytes. You will be taken to the next level of understanding biodiversity with particular reference to vascular spore plants. Pteridophyte is the first land vascular photosynthetic plants. They differ from angiosperm because their leaves have apical meristem that continues to grow in length for some time. nd from other spore producing plant by bearing spores on the lower surface. They are important not only for academic teaching, but also for their unique ferns and allies for aesthetic beautification of our environment. Furthermore, your knowledge of the field (Pteridology) will makes you more conscious of their abundance and important roles to humans. Especially for those of you that are going to become famous Pteridologists, as well as those that require the knowledge in their field of study. www.bupoyesiku.net ~ 3 ~ Department of Plant Science
Introduction Pteridology is the study of Pteridophytes. Like bryophytes and other non-vascular plants they primarily trap solar energy directly from the atmosphere and convert it to food. They form an advance producer in terrestrial food web of a typical ecosystem. Main Content Background of Pteridophytes Pteridophytes are the first vascular plant with xylem and phloem. They reproduce by spores. Thus they are called vascular cryptogams. It is important to know that the seed plants are probably descendants of certain extinct members of pteridophytes, Progymnosperms. It is therefore obvious that some members are polyphyletic, from more than one ancestor. In addition, pteridophytes, probably evolved from the advanced green algae at about the same time as the first vascular seed plants because they both share multicellular sex organs, but the green algae lack vascular tissue. Reproduction in Pteridophytes Vegetative reproduction There are two describable types of vegetative reproduction in pteridophytes. Death of older portion of rhizome with separation of growing apices. Formation of buds on leaves, although very rare. www.bupoyesiku.net ~ 4 ~ Department of Plant Science
sexual reproduction Figure1.1 Fertile Fern frond. Rachis (), Pinnule (B), Sporangia (C) sexual reproduction occurs in the sporangia of the sporophytes. Spores are gathered together into a group called sori, borne under the leaves surface. The sporangium form spore mother cells that meiotically form spores. When mature spores are dispersed and germinate under favorable conditions they produce a fertile and sterile fronds. Sexual reproduction The undersurface of the green heart-shaped gametophyte bears the rhizoids, antheridia and archegonia (Fig 1.2). Fertilization depends upon a water film. The resulting embryo sporophytes compose of rhizines (roots), fronds (leaves). www.bupoyesiku.net ~ 5 ~ Department of Plant Science
B C D Fertilization G E F Figure 1.2 Simplified sexual life cycle in Pteridophyte. Heart-shaped gametophyte (), Female gametangium (B), Male gametangium (C), Rhizoid (D), Young sporophyte (E), Rhizine (F), Spores (G). Classification of Pteridophytes Under the current trend in classification, living members of pteridophytes consist of four major divisions, Psilotophyta (whisk ferns) Lycopodiophyta Sphenophyta and Pterophyta. It will interest you to know that Lycopodium spp. (Club moss) share resemblance with mosses and was in the past mistakenly classified under the Bryophyta. www.bupoyesiku.net ~ 6 ~ Department of Plant Science
Characteristics of Pteridophytes Most fronds (leaves) are compound, although some are simple Fertile leaves with spore on the undersurface and sterile leaves Sporophyte is the dominant plant (independent of gametophyte) Gametophyte (prothallus) is free living small green heart-shaped plant Leaves, large and pinnate (fronds) Circinate vernation or fiddlehead (coiling leaves of young fern) Stem or rhizome in horizontal underground near soil surface Spores are house in sacs called sporangium under the leaves Spore germinate to give filamentous and later green heart-shaped prothallus Two types of spores (microspores and megaspores) Diversity of Forms in Pteridophytes Pteridophytes have two alternating plant bodies the gametophyte and sporophyte. Gametophyte for the first time in spore producing plants is dependent on the sporophytes for nutrient supply. The form of the gametophyte is heart-shaped and that of sporophyte is pinnate compound leaves (fronds). t this point it is important you to acquire the necessary skill to distinguish between the gametophyte of a thallus liverwort and that of a pteridophyte. Club mosses (Lycopodium cernuum): Go online to view the images of club mosses Spike mosses (Selaginella serpens): Go online to view the images of spike mosses www.bupoyesiku.net ~ 7 ~ Department of Plant Science
B C Figure 1.3 Portion of the shoot of Selaginella serpens collected from the OOU BIOME, go-iwoye, Nigeria. Lower large leaf (), Upper small leaf (B), Rhizine (C) Quillwort (marsh plant with rosette of tubular leaves, spores at the base): Go online to view the images of Quillwort Marattioid fern: Go online to view the images of Marattioid fern Horsetails (Equisetum spp.): Go online to view the images of horsetail. Whisk ferns (Psilotophyta): Go online to view the images of Whisk ferns. dder s tongue and Grape ferns (Ophioglossophyta): Go online to view the images of adder s tongue and grape ferns. Leptosporangiate fern (the largest member of ferns): Go online to view the images of ferns www.bupoyesiku.net ~ 8 ~ Department of Plant Science
Habitats of Pteridophytes s you have learnt in previous lectures, Pteridophytes are also native citizen of the entire world. They grow in great diverse habitats except in the marine Ocean. They are found in water as well as on land in marshy ground in shady situation. Major groups of substrate on which Pteridophytes grow are as outline here. Trees (branch, neck and trunk) Rock (cracks and crevices) Decaying woods and plant debris on forest floor Bare ground rtificial structures (culvert and old fences) Ecology of Pteridophytes Pteridophytes are also important plants in the ecosystem. Pteridophyte members have functional stomata on the sporophytes. There has never been a record of pteridophyte fixing nitrogen gas into nitrate for other plant use. Other ecological importance of Pteridophytes is enumerated here. Capture and recycling of nutrients wash with rainwater from the atmosphere. Binding soil surface to prevent erosion Providing seed beds for higher plants Highly sensitive to habitat disturbances Poor indicators of atmospheric pollution Economic uses of Pteridophytes Besides the ecological role, pteridophytes have great economic and aesthetic values. Current trend in the use of ferns have stimulated interests in the field of pteridophytes. Leaves of ferns are traditionally used in floral arrangements. Some of the economic values are stated here. Leaf buds (fiddle heads) of some ferns are commercially harvested and canned or frozen for food www.bupoyesiku.net ~ 9 ~ Department of Plant Science
Spores (Club moss) in making gunpowder and to create dramatic lighting effects because they can easily and quickly ignite. Spore powder is use to coat inside of rubber gloves to enhance smooth insertion of fingers and to reduce sweat irritation The spore powder (club moss) is used in the pharmaceutical industry to coat tablets to protect them from moisture The herb is usually referred to as vegetable sulfur Conclusion In this last lecture note, you have learnt how to recognize the members of pteridophytes as a group of spore producing plants. t the end of this lecture you must have learnt how to recognize, and where to find the Pteridophytes. Focus on the usefulness, if encouraged, the use of Pteridophytes as biomonitor of environmental pollution and vegetation disturbances will be a wise decision. It can alert us of impending danger in our immediate environment. Summary Having study this lecture note, you should: Have some understanding of members of pteridophytes Have a better idea of the characteristics that separate pteridophytes from other groups of cryptogams Be ready to get going with identification of the members on the field Understanding contributions of pteridophytes to our lives References/Further readings/links www.bupoyesiku.net ~ 10 ~ Department of Plant Science
Test Yourself Questions (TYQ) Matric No Department ttendance-code Session/Student s Level C Question TRUE FLSE 1. ll pteridophytes are non-vascular plants X 2. Pteridophytes are first non-vascular seed plants X 3. Spike moss is a pteridophyte X 4. Progymnosperms is an ancestor of seed plant X 5. Fiddle heads are observed only in ferns X 6. fern sporophyte is leafy X 7. Fern gametophyte is capable of fixing nitrogen in the soil X 8. Spores in Pteridophyte form future fertile and sterile fronds X 9. Stem of a fern is always visible ground X 10. Sexual organs in fern are found on gametophyte X Comment: www.bupoyesiku.net ~ 11 ~ Department of Plant Science