The telome theory, therefore, gives a satisfactory explanation of the evolution of leaves, and of sporangiophores, in this group. The sporophyte was the dominant phase of the life cycle of these early pteridophytes. In all pteridophytes the dominant plant is the sporophyte brown below with the gametophyte blue below shortlived. On the basis of their anatomy jeffrey in 1902 divided the vascular plants into two types or stocks. Read the introductory remarks and list of characteristics of the bryophytes p. Pteridophytes introduction, authors and addresses, systematic list, glossary, and key to tribes. Characteristics of pteridophytes, morphology of pteridophytes, reproduction of pteridophytes, homosporous and heterosporous pteridophytes, megaspore and microspores, gametophytes of pteridophytes, fertilization, zygote and embryo of pteridophytes, life cycle. Eichler 1883 regarded cryptogamae as a subdivision of the plant kingdom which included club mosses, horsetails, and ferns. Zimmermanns telome theory of megaphyll leaf evolution. Unlike the ferns, which are a highly successful, flourishing group, the fern allies as we call the other pteridophytes are virtually living fossils. Primitive siphonostele protostele with central pith. Tippo 1942 considered tracheophyta to include pteridophytes and spermatophytes. The origin of the sporophyte in land plants represents a fundamental phase in plant evolution.
There are about eleven thousand different species of pteridophytes, making them the most diverse land plants. Pteridophyta characteristics, life cycle, classification. Occurrence and evolution of pteridophytes biology boom. 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.
Classification of pteridophytes for a long time the division pteridophyta includedthe ferns, lycopods and horsetails. The classes in this division represent some of the oldest lineages of land plants. Pdf on apr 18, 2002, paul kenrick and others published the telome theory find, read and cite all the research you need on researchgate. At the end of the course, the students are expected to have good working knowledge in the field of plant science. They are psilopsida, psilotopsida, lycopsida, sphenopsida, pteropsida and progymnospermopsida. Apogamy and parthenogenesis origin and evolution of pteridophytes telome theory and enation theory polyploidy and chromosome number stelar system. The pteridophytes occupy an intermediate position between the bryophytes and gymnosperms. This author lists a total of 671 references, but only one work had been carried out in brazil miraglia et al. These processes may have occurred in various sequences in different groups of vascular plants. With the commencement of monsoon about mid june, the ferns and fernallies start growing vigourously and luxuriantly. In this book, zimmermann describes the evolutionary sequence of modifications leading up to the appearance of megaphyll leaves on ancestral early axial vascular land plants.
Pteridophyta do not produce seeds but they produce spores. They formed the dominant part of the earths during palaeozoic and mesozoic periods. The true story seems to be lost in antiquity and perhaps will never. One weakness of the telome theory zimmermann, 1952 is that, although processes of organ evolution are well explained, their developmental basis remains unclear kenrick, 2002. The sterile gradually flattened while the fertile telome had a gradual reduction of the basal sterile portion, with the result, the sporangium came to lie on the leafy appendage below fig. They formed the dominant part of the earths during palaeozoic and mesozoic periods on soral evolution.
Structure, reproduction, affinities and evolutionary trends of. In the case of leaves, zimmermann essentially envisaged the transformation of a stem into a. Some pteridophytes are aquatic and some are epiphytes. The pteridophytes spore bearing vascular plants have been around for 408 milloin years. These are the telome theory and the enation theory. This fern life cycle is representative of most pteridophytes.
Compound sporangiophores, like those of equisetum, are syntelomes. Unlike the bryophytes, these plants are in the mainstream of land plant evolution and eventually gave rise to the seed plants. The pteridophytes were not necessarily the first vascular land plants see kenrick and crane 1997. The theory that the leaves megaphylls of ferns and seed plants evolved by the modification of terminal branches telomes of stems. As they produce neither flowers nor seeds, they are referred to as cryptogams. Buy isbn9781403930309 at 16% discount by macmillian india ltdnew delhi. A concept based exclusive material pteridophytes, gymnosperms. Pteridophytes pteridophtyes are a phylum of plants. Despite early success in pteridophytes and gymnosperms, the telome theory never really had a major impact on the field of angiosperm morphogenesis. Stelar organization and evolution of stele in pteridophytes. Pteridophyta is the most highly evolved group among the cryptogams. The different species of selaginella are grown as the garden plants. Telome and the evolution of the independent sporophyte among pteridophytes.
The evolution, morphology, and development of fern leaves. The phylloids are the prototypes of the microphyllous foliage leaves. Phytochemical studies in pteridophytes growing in brazil. Telome theory abulais shomrat january 12, 2020 cryptogams leave a comment 70 views a telome is defined as branch having no leaves but dichotomous branching at either apex or at base or both i. Basic types of steles protostele central xylem, surrounding phloem. This is a portion of the telome theory as proposed by zimmermann 1952 and 1959, who proposed that all of the main plant organs can be derived from simple rhynialike axes called mesomes sterile axes and telomes fertile axes.
Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as cryptogams, meaning that their means of reproduction is hidden. This pdf version does not have an isbn or issn and is not therefore effectively published melbourne code, art. The steps leading to the formation of a megaphyll are given in figure 11. According to telome theory the earliest levees are flattened telomes or phylloids, and the sporangium in all cases, together with its stalk or sporangiophore, is a fertile telome.
A pteridophyte is a vascular plant with xylem and phloem that disperses spores. Characteristics of pteridophytes, morphology of pteridophytes, reproduction of pteridophytes, homosporous and heterosporous pteridophytes, megaspore and microspores, gametophytes of pteridophytes, fertilization, zygote and embryo. While telome theory accounts for the origin of both microphylls and megaphylls, enation theory explains only the origin of microphylls. Embryophyte cells also generally have an enlarged central vacuole enclosed by a vacuolar membrane or tonoplast, which maintains cell turgor and keeps the plant rigid. In its general form, the telome theory proposes that, by combining and modifying simple multicellular telomes through one or more developmental processes, it is possible to explain all extant and extinct plant morphologies. The pteridophytes are an economically important group of plants. Journal of economic education 19692015 books by language journal of autism and developmental disorders 19712014 journal of paediatric dentistry. However, the growth habit of the earliest members e. Most pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions. Some of the characters of pteridophytes are as follows. I the emergence of ferns is best to be compared with a looming up from the fog. Most pteridophytes are terrestrial and grows in moist and shady places while some flourish well in open dry places.
The modern classification of pteridophytes have been suggested by many scientist according to the sporne1975 pteridophytes have been classified into six classes. Pteridophyta living in water are known as hydrophyte, sticking in other plants are called epiphyte and living in residue or waste of other plants are known as saprophyte. Content is available under the creative commons attribution share. They are the vascular plants those having xylem and phloem tissues that reproduce by releasing spores rather than seeds, and they include the highly diverse true ferns and other graceful, primarily forestdwelling plants. Pteridophytes general characters ppt general characteristics, life cycle and reproduction of pteridophytes ppt what are pteridophytes. According to zimmermann, these telomes or telome trusses of primitive rhynia type of vascular plants have been subjected to certain evolutionary processes in varying degrees among the various taxonomic groups. The sexuality of pteridophytic gametophytes can be classified as follows.
Merits and demerits of telome theory biology 840 words. At first you see forms vaguely resembling ferns and bit by bit the image becomes sharper. The degree of master of science in plant science aims to introduce the students to various aspects of plant biology. Occurrence and evolution of pteridophytes with its origin and economic importance in pteridophyta is a group of ancient plants. Engler 1886 suggested the term embryophyta to include bryophytes, pteridophytes, and spermatophytes. Figure 4 three processes from the telome theory proposed to be involved in megaphyll evolution redrawn from zimmermann, 1952. Zimmermanns telome theory has been widely accepted for over seventy years as the leading explanation for this evolutionary innovation.
Wilson dartmouth college, hanover, new hampshire introduction morphologists have long been concerned with the fundamental nature of the vascular plant bodywith the relationships between root, stem and leaf, and with the origin of reproductive structures. It envisages that firstly, instead of the primitive equal dichotomous branching of the stem, there developed a main axis with lateral side branches. Les sporophylles, portant les microsporanges, sappellent des microsporophylles et celles, portant les macrosporanges, des. Mar 23, 2018 the pteridophytes are an economically important group of plants. It is speculated that life began in the oceans, and through millions of years of evolution, life slowly adapted on to dry land. Linnaeus 1754 included them in the class cryptogamae kruptos hidden, gamos marriage. It envisages that firstly, instead of the primitive equal dichotomous branching of the stem. In common with all groups of multicellular algae they have a life cycle which involves alternation of generations. Followers of the telome theory believe that in a telome truss, of the two telomes the upper was fertile and the lower sterile. Today this subject is controversial, and scarcely considered in textbooks and journals of botany, in spite of its importance.
One is the antithetic theory interpolation theory or heterologous theory, proposed by bower. Most of the pteridophytes ferns and fernallies show their luxuriant and vigorous growth during the rainy season particularly in the hilly regions usually above 1400 m altitude. The printed version, however, was effectively published on 6 june 20. Pteridophytes or pteridophyta, in the broad interpretation of the term, are vascular plants plants with xylem and phloem that reproduce and disperse via spores. According to telome theory first proposed by zimmermann 1930, 1938, primitive pteridophytic shoot was naked and dichotomously branched. Usually a fern is defined as a cryptogam with sporangia evolving from the leaf. They are preserved in the form of fossils or coal deposits. Calamophyton, protohyenia and hyenia was a long way from the theoretical ancestral type. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and freeliving. Ferns, horsetails often treated as ferns, and lycophytes clubmosses, spikemosses, and quillworts are all pteridophytes. Reproductive biology of pteridophytes springerlink. This page was last modified on 26 december 2014, at 02.
This theory is based on fossil record and synthesizes the major steps in the evolution of vascular plants. Phytochemical studies in brazilian pteridophytes soeder 1985 reported a large inventory of papers that appeared between 1966 and 1984 on the chemical constituents of pteridophytes. This page was last modified on 26 december 2014, at 03. Some pteridosperm stems and fructifications with particular reference to the medullosae. The sporophyte is the conspicuous and familiar plant body. They proposed the stellar theory, according to which the root and stem have the same basic structure consisting of two fundamental units the cortex and the central cylinder. Schmidt recognized the two principal types of steles in pteridophytes.
The lycopodopsida clubmoss class was the first branch of the evolutionary tree. The first vascular plants rapidly diversified to cover the earth. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. And among the first of the plants to truly live on land were the pteridophytes.
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