Pdf on apr 18, 2002, paul kenrick and others published the telome theory find. Ferns can be used to illustrate the life cycle stages common to all pteridophytes. It envisages that firstly, instead of the primitive equal dichotomous branching of the stem, there developed a main axis with lateral side branches. Merits and demerits of telome theory biology 840 words. 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. Pteridophyta have life cycle known as metagenesis with two generations, they are sporophyte and gametophyte generations. Telome and the evolution of the independent sporophyte among pteridophytes. 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. Stelar evolution in pteridophytes ppt types of steles and its evolution in pteridophytes ppt what is stele. They are psilopsida, psilotopsida, lycopsida, sphenopsida, pteropsida and progymnospermopsida. 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.
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. Calamophyton, protohyenia and hyenia was a long way from the theoretical ancestral type. This is commonly interpreted in terms of the more highly specialized leaves of the leptosporangiate ferns as corn. Stelar evolution in pteridophytes linkedin slideshare. The distinction between main stems and strongly branched lateral stems evident in species such as p. Tippo 1942 considered tracheophyta to include pteridophytes and spermatophytes. Be aware that some people use this term just to refer to ferns. Apogamy is the development of an unusual haploid sporophyte from the gametophyte without the fusion of gametes. The telome theory, therefore, gives a satisfactory explanation of the evolution of leaves, and of sporangiophores, in this group. This theory is based on fossil record and synthesizes the major steps in the evolution of vascular plants. The different species of selaginella are grown as the garden plants. Content is available under the creative commons attribution share.
Natural apogamy is common in ferns like dryopteris, adiantum, osmunda, pteris etc. This life cycle is also believed to foster quick reproduction in connection with brief damp periods. However, the growth habit of the earliest members e. Pteridophyte definition of pteridophyte by merriamwebster. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. Download objective type questions of pteridophyta pdf visit our pdf store. They are preserved in the form of fossils or coal deposits. The empirical basis of botanical systematics has been broadened far beyond the realm of macromorphological traits on which systematists have based their decisions for more than 200 years.
Primitive siphonostele protostele with central pith. The phylloids are the prototypes of the microphyllous foliage leaves. Problems of cytology and evolution in the pteridophyta by manton, i. 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 and alternation of generation. Floristic composition of alabama piedmont floodplains across a gradient of stream channel incision. Pteridophytes ferns and lycophytes are free sporing vascular plants that have a life cycle with alternating, free living gametophyte and sporophyte phases that are independent at maturity. Followers of the telome theory believe that in a telome truss, of the two telomes the upper was fertile and the lower sterile. Before considering the telome theory itself, it is desirable to point. Stelar theory, components of stele, different types of steles in plants, protostele. Pteridophyta in the broad interpretation of the term are vascular plants that reproduce via spores. Pteridophyta objective type questions pdf download. 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. Zimmermanns telome theory of megaphyll leaf evolution.
Zimmermanns telome theory has been widely accepted for over seventy years as the leading explanation for this evolutionary innovation. Les sporophylles, portant les microsporanges, sappellent des microsporophylles et celles, portant les macrosporanges, des. Pteridophyte definition is any of a division pteridophyta of vascular plants such as a fern that have roots, stems, and leaves but lack flowers or seeds. The origin and early evolution of vascular plant shoots. Pteridophytes differ from mosses and seed plants in that both generations are independent and free living, although the sporophyte is generally much larger and more conspicuous. Thus, free water is not required for swimming sperm. Pteridophyta characteristics, life cycle, classification. Compound sporangiophores, like those of equisetum, are syntelomes. Haeckel 1866 called these groups of plants as pteridophytes because of their pinnate or featherlike fronds leaves. 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. The sexuality of pteridophytic gametophytes can be classified as follows.
The modern classification of pteridophytes have been suggested by many scientist according to the sporne1975 pteridophytes have been classified into six classes. The classes in this division represent some of the oldest lineages of land plants. There are about eleven thousand different species of pteridophytes, making them the most diverse land plants. The pteridophytes occupy an intermediate position between the bryophytes and gymnosperms. Pteridophyta is designed to fulfill the needs of undergraduate and postgraduate students of botany. The term pteridophyte refers to vascular plants with independent gametophytes and motile sperm that are usually classified into 4 divisions that comprise nearly 40 families. Reproductive biology of pteridophytes springerlink. The printed version, however, was effectively published on 6 june 20. Publication date 1962 topics pteridophyta, botany morphology publisher london, hutchinson university library. On leafarchitecture as illuminated by a study of the pteridophyta. Apospory is the development of unusual diploid gametophyte from the vegetative parts of sporophyte and not from the spores. Read the introductory remarks and list of characteristics of the bryophytes p. This assessment will assess how well you understand the life.
This page was last modified on 26 december 2014, at 02. 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. The sporophyte is the conspicuous and familiar plant body. Some pteridophytes are aquatic and some are epiphytes. Most pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions. The lycopodopsida clubmoss class was the first branch of the evolutionary tree.
Schmidt recognized the two principal types of steles in pteridophytes. Pteridophytes and forbs with facwobl designations are associated with sites exhibiting referencetype geomorphic conditions, i. The telome theory of leaf evolution proposed that transformative evolutionary processes of unequal branching overtopping, rearrangement of lateral branches into a single plane planation and infilling of spaces between branches with laminar tissue webbing generated euphyllophyte leaves. In this course we are going to use the term pteridophyte to refer to nonseed vascular plants, i. Challenging the paradigms of leaf evolution new phytologist trust. They formed the dominant part of the earths during palaeozoic and mesozoic periods. App download implementation through twitter app card. The bryophytes are a group of simple land plants which in many ways are an evolutionary dead end. Pteridophytes are a group of plant species that have grown on this earth for over millions of years. The pteridophytes are an economically important group of plants. Pteridophytes definition of pteridophytes by medical. The current trends in the subject are explained in a simple, lucid and understandablewriting style. The dominant theory of leaf evolution is the telome theory zimmermann, 1952. The telome theory offers one explanation for the nature of the aerial.
The body of the sporophyte is well differentiated into roots, stem and leaves. Occurrence and evolution of pteridophytes biology boom. Pteridophytes, paleobotany, environmental biology and ecosystem management. Some of the characters of pteridophytes are as follows. Pteridophytes general characters and life cycle of ferns email. Apospory and apogamy in pteridophytes biology discussion. Ferns are known to have an attractive foliage and therefore, they are grown as ornamental plants in gardens and homes. Basic types of steles protostele central xylem, surrounding phloem. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and free living. The pteridophytes are known to be of high economic importance. Pteridophytes introduction, authors and addresses, systematic list, glossary, and key to tribes. All pteridophytes have a true alternation of generations, in which a dominant sporophyte generation produces spores through meiosis, and a free living gametophyte generation forms gametes egg and sperm by mitosis. The dominant theory of leaf evolution is the telome theory zimmermann, 1952, which suggests that megaphylls arose by overtopping, planation and webbing of subsets of shoots within a. The steps leading to the formation of a megaphyll are given in figure 11.
Engler 1886 suggested the term embryophyta to include bryophytes, pteridophytes, and spermatophytes. The pteridophytes are vascular plants plants with xylem and phloem that produce neither flowers nor seeds, and are hence called vascular cryptogams. According to telome theory, a megaphyllous leaf originates as per the following steps. There are no page or colour charges and a pdf version will be provided for. The life cycle of pteridophytes is probably best exemplified by the general life cycle of the fern. Pteridophyta mcq multiple choice question and answer pteridophyta mcq with detailed explanation for interview, entrance and competitive exams. This thoroughly revised edition, besides retaining almost all topics of the first edition, now also discusses topics like economic importance of pteridophyta, some characteristic features of pteridological divisions, some more rhynophytes, trends of evolutionary specialization in psilophytes, a note on silurian and pre.
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