Heterosporous pteridophytes produce two types of spores. The existence of heterospory has importance in the origin and evolution of seed. They also encompass a greater range of habit than any other group of tracheophytes. Download fulltext pdf origins of heterospory and the seed habit. Pteridophytes have many unique characters in both structural and reproductive features. What are the similarities between homosporous and heterosporous pteridophytes. Seed is the ripened ovule with integuments formed after fertilization. Pteridophytes general characteristics general characters of pteridophytes the vascular cryptogams pteridophytes are plants with feather like leaves. In certain species of selaginella only one megaspore develops within the mega sporangium. The different species of selaginella are grown as the garden plants. Some of the characters of pteridophytes are as follows.
Rakesh jena rated it it was ok feb 24, free pdf ebooks users guide, manuals, eingh about boany pandey jain botany book pdf download ready for download search result for singh pandey jain botany book pdf download list of ebooks and manuels about singh pandey jain botany book pdf download enter search terms. Such peridophytes are known as homosporous and this phenomenon is known as homospory. It is characterized by morphologically dissimilar spores produced from two types of sporangia. Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral condition, homospory. A seed ovule may be defined as an integumented indehiscent megasporangium. Heterospory was one of the most innovative adaptations in land plants, independently evolving in multiple lineages. The evolution of the seed habit is related to the retention of the megaspore. They are a type of vascular plants which possesses xylem and phloem tissues.
A concept based exclusive material pteridophytes, gymnosperms. Key difference homosporous vs heterosporous pteridophytes pteridophyta is the largest phylum of the kingdom plantae. Types of stele and its evolution in pteridophytes duration. Some pteridophytes are aquatic and some are epiphytes. These plants posses some of the characteristics which are precursors of the seed habit and these are. Fig i rt textbook lifihistorv of a homosporous pteridophyte. Thomson department of botany, university of toronto some months ago there were two notes in. The delimitation of families of extant pteridophytes had been very controversial in the past but a consensus has been emerging on overall. Even today, many tribal communities and rural populations are dependent heavily upon the natural resources obtained from the surrounding forest regions for treatment of various ailments and diseases. However, very little is known about the adaptive significance of heterospory. Biology experiment protocols and flow charts, diagrams for biology record work. Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular plants. In selaginella, nutritive tissue called tapetum is present.
Heterospory evolved first in pteridophytes such as selaginella and salvinia. The pteridophytes show heteromorphic alternation of generation. A seed consists of an embryo, stored food and a seed coat. Ebook an introduction to pteridophyta as pdf download. Heterospory and seed habit in pteridophytes botany. Structure, development and evolution of sorus in filicales. Heterospory can be ascribed to result from expression of one sex and repression of other in particular regions. Heterospory and seed habitat in pteridophytes easybiologyclass. Your browser does not currently recognize any of the video formats available. Heterospory originated in some pteridophytes like selaginella. Pteridophytes reproduction mainly occurs via the spores.
Heterospory and seed habit in pteridophytes ferns evolution of the seed is one of the most crucial adaptations in phanerogams for successful survival in terrestrial habitat. Jul 20, 2019 importance of heterospory and seed habit of ferns 581 words abstract the evolution of the seed is one of the major events in the history selaginlela land plants. In most of the heterosporous plants, the gametophyte is restricted to very few cells. The heterosporous fern platyzoma microphyllum has exosporic photosynthetic gametophytes. Most of the pteridophytes produce one kind of similar spore. Alternative views of character state distributions in the evolution of heterospory and the seed habit.
In selaginella germination of megaspores is insitu that is occurs within the mega sporangium and produces the female gametophyte. The book also discusses topics like heterospory, seed habit, leaf phylogeny, stellar system, alternation of generations, regeneration in general and special role of germ cellsegg and sporein life cycle. Each microsporangium contains a large number of microspores whereas. They are differentiated into micro and megasporangia. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the. The main difference between homospory and heterospory is that the homospory is the production of a single type of spores with the same size whereas the heterospory is the production of two types of spores, megaspores and microspores, with different sizes.
During this period important heterosporous genera were lepidocarpon, lepidostrobus, mazocarpon, plaeuromeia, sigillariostrobiis members ov lycopsid calamocarpon, calamostachys, palaeostachys. However, there are some pteridophytes which produce two different types of spores differing in size. Pteridophytes constitute a significant and important group in the plant. Evolutionary significance of heterospory and seed development in. This is an important step in evolution and is found in selaginella and salvinia among the pteridophytes. The next big step in evolution was heterospory or formation of two different types of spores, the smaller ones. Pteridophyta general characteristics, classification and stelar system pteridophyta are the most primitive vascular plants. This adaptive ability of heterospory increases reproductive success as any type of environment favors having these two strategies. We use cookies to make interactions with our website easy and meaningful, to better understand the use of our services, and to tailor advertising. How far pteridophytes approach seed habit or fall short of it is a matter in itself but our understanding of the phenomenon of heterospory is far from complete. Most pteridophytes are terrestrial plants and thrive well in abundant moisture and shade while some flourish well in open, dry situations especially in xeric conditions. Details of different genera in terms of morphology, anatomy, reproduction and sexuality have been explained with due diagrams. What is the difference between homosporous and heterosporous pteridophytes.
Furthermore, most seedless vascular plants and bryophytes are homosporous while all seed plants and some pteridophytes. There is further elaboration of the megasporangium so as to enable it to be an ideal starting point for the development of a new plant. To watch the full class on pteridophytes and gymnosperms for your neet exam for free, click. Oct 10, 2019 heterospory and origin and evolution of seed habitat in land plants pteridophytes. The spores are differentiated into microspores and megaspores borne on the microsporangium and megasporangium. Each microsporangium contains a large number of microspores whereas each megasporangium contains usually only four megaspores. When such attempts lime been made the definitions show striking contrasts in content and or emphasis table i.
Stelar evolution in pteridophytes, heterospory and origin of seed habit. Pteridophytes differ from bryophytes in that the sporophyte is branched and generally much larger and more conspicuous, and from seed plants in that both generations are independent and freeliving. Slowly in higher organisms sexual dimorphism started to occur. They occur in a wide variety of habitats and dominate todays flora. Heterospory and seed habit in pteridophytes plant life. Most of these have been found as detached organs in the tournaisian basal mississippian of southern scotland heterospory and the origin of the seed habit textfig. Selective forces in the emergence of the seed habit haig. Fern leaves used in floral arrangements are a major industry in florida, and in some cultures tree. Pteridophyta characteristics, life cycle, classification. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the phenomenon of seed habit, a characteristic feature of the spermatophytes. Heterospory and gametophytic unisexuality are not necessarily evolu tionary antecedents of endospory. The most successful origin of heterospory ultimately resulted in the great diversity of seed plants. Since their first appearance in the late devonian, seed plants have come to dominate almost every terrestrial ecosystem.
An introduction to pteridophyta start download portable document format pdf and ebooks electronic books. Full text of the origin of gymnosperms and the seed habit. Mar, 2020 building construction handbook by roy chudley pdf. Heterospory and gametophytic unisexuality are not necessarily evolutionary antecedents of endospory. Heterospory is a condition of the production of more than one type usually two of spores in a single plant. What is the difference between homospory and heterospory. Heterospory and seed habit in pteridophytes ferns plant science. The microsporangia contain microspores whereas megasporangia contain megaspores in them.
A heterosporous life history occurs in some pteridophytes and in all seed plants. Click here to visit our frequently asked questions about html5. The sporophyte is the conspicuous and familiar plant body. Heterospory and the origin of the seed researchgate. Heterospory produced the first endosporic inside the spore wall type of gametophyte development in land plants. Importance of heterospory and seed habit of ferns 581 words abstract the evolution of the seed is one of the major events in the history selaginlela land plants. The two kinds of spores the microspores and the megaspores are found on the microsporangia and megasporangia respectively. The microspores develop into male gametophyte whereas the megaspores give rise to female gametophyte. T h e seed habit was well established by the lowermost mississippian period and quite a large diversity of fossil ovules is now known. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and freeliving. They are the first evolved plant group with vascular tissue system for the conduction of water and food materials. An introduction to archegoniate plants buy online on lowest. The sexuality of pteridophytic gametophytes can be classified as follows.
In both types, the gametophyte obtains the nutrition from the sporophyte. They are the second most diverse land plants after angiosperms. Read heterothally and the seed habit versus heterospory, new phytologist on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Heterospory means production of two different sizes of sporesmegaspore and microspore. However, there are some pteridophytes which produce two different types of. Traditional view, in which all major variations on vascular plant life history are projected as steps in trend toward increasing enlargement and protection of the female gametophyte. Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit. Each microsporangium contains a large number of microspores whereas each megasporangium contains usually only. Seed habit the condition of heterospory in selaginells constitute one of the very important phases in the evolution of the plants. The role of heterochrony article pdf available in taxon 381. Importance of heterospory and seed habit of ferns 581 words this summarize the successful steps by genus selaginella towards seed habit. Life cycle, in biology, the series of changes that the members of a species undergo as they pass from the beginning of a given developmental stage to the inception of that same developmental stage in a.
The sexuality of pteridophyte gametophytes can be classified as follows. David haig and mark westoby, selective forces in the emergence of the seed habit, biological journal of the linnean society, 38, 3, 215238, 2008. Heterospory was a key event in the evolution of both fossil and surviving plants. Wiley online library divya darshan pant and rita singh, on the possible occurrence of anisospory in some hepaticae, botanical journal of the linnean society, 100, 2, 183, 1989. Biology question bank 80 mcqs on plant kingdom answered. According to rashid1976, only 9 genera of pteridophytes show heterospory,i. In this paper, we consider the suite of characters that define the seed habit, and discuss the probable selective pressures that produced each character. In the seed bearing plants there are two kinds of spores. Heterospory and seed habit in pteridophytes ferns plant. The seed habit is the most complex and diverse means of sexual reproduction in vascular land plants. Most of this diversity in angiosperms occurred during cretaceous time. Retention of the female gametophyte within the megasporangium on the parent plant for proper parental care of new embryo. For many years it has been generally assumed by botanists that in angiosperms, as in the heterosporous pteridophytes, the megaspores are larger than the microspores.
Heterospory video from neet syllabus botany plant kingdom. An introduction to pteridophyta top results of your surfing an introduction to pteridophyta start download portable document format pdf and ebooks electronic books free online rating news 20162017 is books that can provide inspiration, insight, knowledge to the reader. Sep 7, 2014 heterospory and seed habit in pteridophytes. The condition of production of two different types of spores in the same species is known as the heterospory.
Importance of heterospory and seed habit of ferns 581 words. The heterospory also reduced the size of gametophytic generation. Heterospory and origin and evolution of seed habitat in land plants pteridophytes. Heterosporyis thusconsideredan importantstepin evolution as it is a precursor to the seed habit. In most lower plants like algae fertilization takes place outside the plant body. Both the spores germinate endosporically to produce gametophytes. Most pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions. Gymnosperms a general account of the characteristic features of gymnosperms. Pdf summary the origin of the seedplant life history, and subsequent diversification of.
Our major conclusion is that most characters are a direct consequence of the origin of heterospory and of natural selection for propagules with larger food reserves. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. Pteridophytes are a group of primitive land plants belongs to the cryptogams. Difference between homosporous and heterosporous pteridophytes. Heterospory and seed habit are often exhibited by a plant possessing a petiole b ligule c bract d spathe. Examples of heterosporous pteridophytes lifeeasy biology.
The seed habit is the most complex and evolutionary successful method of sexual reproduction. Pteridophytes biology encyclopedia plant, body, different. Those from the small spores are filamentous, with few rhizoids and produce. In this article we will discuss about heterospory and seed habit in pteridophytes. Thus the origin of the seed habit is a logical progression that began with homospory, was followed by stages of heterospory, and culminated into the seed. When such attempts lime been made the definitions show striking contrasts in content andor emphasis table i. The development of zygote into young embryos takes place within the female gametophyte which is retained on parent sporophyte. Evolution of the seed habit consists of at least two independent problems. Summary the origin of the seedplant life history, and subsequent diversification of seed. Jul 17, 2019 anybody can ask a question anybody can answer the best answers are voted up and rise to the top. Heterospory and seed habitat origin of seeds and seed habitat in vascular plants from heterospory heterospory is the production of two or more types of spores. The presence of two kinds of spores in the same species is known as heterospory.
No pteridophytes are cultivated as crop plants, but the leaf buds fiddleheads of some ferns are commercially harvested and canned or frozen. Heterosporous pteridophytes are the plants that produce two types of spores i. It is a condition found in some plants in which a plant produces more than one type of spores. Pteridophyta general characteristics, classification and. Full text of the origin of gymnosperms and the seed habit see other formats stop early journal content on jstor, free to anyone in the world this article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in the world by jstor. Mar 23, 2018 the pteridophytes are an economically important group of plants. A seed is that ovule which contains an embryo developed as a result of fertilization. Being the first true land plants they include in their bodily features the results of many experiments that nature conducted with the sporophytic plant body on a primordial terrestrial habitat. One of the most important advantages of heterospory is the formation of seed habitat.
The retention of megaspores and the dispersal of microspores allow for both dispersal and establishment reproductive strategies. A few pteridophytes are aquatic while still others are epiphytes. Have naked seeds as the ovules are not enclosed by any ovary wall and remain exposed. Heterospory advanced to the seed habitat in land plants. Heterospory and the origin of the seed habit deepdyve. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext.
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