Pteridophyta characteristics, life cycle, classification. It is speculated that life began in the oceans, and through millions of years of evolution, life slowly adapted on to dry land. Sumita, assistant professor, department of botany, pggc11, chandigarh. The telome theory, therefore, gives a satisfactory explanation of the evolution of leaves, and of sporangiophores, in this group. The sporophyte is the conspicuous and familiar plant body.
The first vascular plants rapidly diversified to cover the earth. A pteridophyte is a vascular plant with xylem and phloem that disperses spores. Content is available under the creative commons attribution share. 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. The steps leading to the formation of a megaphyll are given in figure 11. Challenging the paradigms of leaf evolution new phytologist trust.
And among the first of the plants to truly live on land were the pteridophytes. Ferns, horsetails often treated as ferns, and lycophytes clubmosses, spikemosses, and quillworts are all 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. Pteridophyta is the most highly evolved group among the cryptogams. This theory is based on fossil record and synthesizes the major. Stelar evolution in pteridophytes linkedin slideshare. However, the growth habit of the earliest members e. Pteridophytes may represent the closest living relatives sister group to the seed plants. 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. Merits and demerits of telome theory biology 840 words. Zimmermanns telome theory has been widely accepted for over seventy years as the leading explanation for this evolutionary innovation. The printed version, however, was effectively published on 6 june 20. Phytochemical studies in pteridophytes growing in brazil.
Some pteridosperm stems and fructifications with particular reference to the medullosae. Compound sporangiophores, like those of equisetum, are syntelomes. Followers of the telome theory believe that in a telome truss, of the two telomes the upper was fertile and the lower sterile. Reproductive biology of pteridophytes springerlink. Zimmermanns telome theory of megaphyll leaf evolution. Tippo 1942 considered tracheophyta to include pteridophytes and spermatophytes. 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 presilurian plants. On leafarchitecture as illuminated by a study of the pteridophyta.
The degree of master of science in plant science aims to introduce the students to various aspects of plant biology. The sterile gradually flattened while the fertile telome had a gradual reduction of the basal sterile portion, with the result, the sporangium came to. Engler 1886 suggested the term embryophyta to include bryophytes, pteridophytes, and spermatophytes. The life cycle of pteridophytes is probably best exemplified by the general life cycle of the fern. Ethnobotanical studies of 40 pteridophytes species by uddin et al. Some of the characters of pteridophytes are as follows. Concerning the evolution of leaves, his telome theory proposed that megaphyll evolution involves three elementary processes that could occur independently of each other figure figure4. As they produce neither flowers nor seeds, they are referred to as cryptogams. Pteridophytes introduction, authors and addresses, systematic list, glossary, and key to tribes.
There are about eleven thousand different species of pteridophytes, making them the most diverse land plants after the. 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 bryophytes are a group of simple land plants which in many ways are an evolutionary dead end. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and freeliving.
The different species of selaginella are grown as the garden plants. 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. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as cryptogams, meaning that their means of reproduction is hidden. 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. Introduction this theory was first proposed by walter zimmermann in 1930. Basic types of steles protostele central xylem, surrounding phloem. The current trends in the subject are explained in a simple, lucid and understandablewriting style. As in seed plants, the greatest diversity of pteridophytes is found in the tropics, with only about six hundred species adapted for life in temperate climates. Buy isbn9781403930309 at 16% discount by macmillian india ltdnew delhi.
Pdf on apr 18, 2002, paul kenrick and others published the telome theory find, read and cite all the research you need on researchgate. This page was last modified on 26 december 2014, at 02. Pteridophytes general characters ppt general characteristics, life cycle and reproduction of pteridophytes ppt what are pteridophytes. This pdf version does not have an isbn or issn and is not therefore effectively published melbourne code, art. 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. 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. These three processes transformed the dichotomous, leafless, photosynthetic axes of the sporophyte of early devonian plants into leaves zimmermann, 1930.
Schmidt recognized the two principal types of steles in. Unlike the bryophytes, these plants are in the mainstream of land plant evolution and eventually gave rise to the seed plants. App download implementation through twitter app card. The distinction between main stems and strongly branched lateral stems evident in species such as p. The true story seems to be lost in antiquity and perhaps will never. There are two theories regarding evolution of bryophytes. Pteridophyta is designed to fulfill the needs of undergraduate and postgraduate students of botany. A concept based exclusive material pteridophytes, gymnosperms. Primitive siphonostele protostele with central pith. The pteridophytes occupy an intermediate position between the bryophytes and gymnosperms. They are psilopsida, psilotopsida, lycopsida, sphenopsida, pteropsida and progymnospermopsida. Sharma 2000 reported the ethnobotanical uses of ferns from rajasthan, india. 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.
The pteridophytes are an economically important group of plants. Evolution of bryophytes according to these theories the evolution in bryophytes is as follows. These three processes transformedthedichotomous,lea. Apogamy and parthenogenesis origin and evolution of pteridophytes telome theory and enation theory polyploidy and chromosome number stelar system. Pteridophytes general characters and life cycle of ferns email. There are no page or colour charges and a pdf version will be provided for each article. Thus, free water is not required for swimming sperm. 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.
Megaphyll leaf evolution was a critical event in earth history that had major consequences for the biotic regulation of the global environment. Thus, these characteristics make them horticulturally important plants. The evolution, morphology, and development of fern leaves. 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. The phylloids are the prototypes of the microphyllous foliage leaves. Some pteridophytes are aquatic and some are epiphytes. Pteridophytes or pteridophyta, in the broad interpretation of the term, are vascular plants plants with xylem and phloem that reproduce and disperse via spores. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. Schmidt recognized the two principal types of steles in pteridophytes. Pteridophytes pteridophytes is a general term for the vascular, free. At the end of the course, the students are expected to have good working knowledge in the field of plant science. Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants. 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.
Be aware that some people use this term just to refer to ferns. 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. Calamophyton, protohyenia and hyenia was a long way from the theoretical ancestral type. Characteristics of pteridophytes, morphology of pteridophytes, reproduction of pteridophytes, homosporous and heterosporous pteridophytes, megaspore and microspores, gametophytes of pteridophytes, fertilization, zygote and embryo of. Mar 23, 2018 the pteridophytes are an economically important group of plants. Zimmermanns theory was really a description of three. This author lists a total of 671 references, but only one work had been carried out in brazil miraglia et al. They also studied the use of pteridophytes as a vegetable and herbal medicine. It envisages that firstly, instead of the primitive equal dichotomous branching of the stem, there developed a main axis with lateral side branches. Most pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions. In common with all groups of multicellular algae they have a life cycle which involves alternation of generations. In this course we are going to use the term pteridophyte to refer to nonseed vascular plants, i. Publication date 1962 topics pteridophyta, botany morphology publisher.
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