Sven Bot Tidskr , 39 , — Suggestions for classification of fossil and recent pollen grains and spores. Svensk Botanisk Tidskrift, 41, — Angiosperms p.
Stockholm: Almqvist and Wiksell. Handbook of palynology—An introduction to the study of pollen grains and spores p. Copenhagen: Munksgaard. Faegri, K. Textbook of pollen analysis 2nd ed. Textbook of pollen analysis 3rd ed. New York: Hafner. Textbook of pollen analysis 4th ed.
Fritzsche, J. Mem Sav Etrang Acad , 3 : St. Petersburg, — Grebe, H. A recommended terminology and descriptive method for spores. Microflore Palaeozoique, 4 : Les Spores, 1, 7— Halbritter, A. Illustrated pollen terminology p. Berlin: Springer. CrossRef Google Scholar. Harris, W. One of the very earliest practical applications of preserved pollen in the reconstruction of changing environments was by the Swedish palynologist Von Post in He studied tree pollen preserved in peat to build a picture of fluctuating climatic conditions during the Quaternary.
In Britain during the 's Raistrick used spores he recovered from coals to recognise different coal seams, but he did not name the spores he found but assigned them an alpha-numeric code. Perhaps the greatest contribution made by a single person was that made by another Swede, Gunnar Erdtman, who from the 's to the 's produced several classic books and papers which remain required reading today. The earliest terrestrial plants are recorded from the late Silurian, and these were homosporous all spores produced are of the same kind.
By the end of the Devonian heterospory had appeared, this still involves dispersal by spores only but both microspores held in a microsporangium and megaspores held in a megasorangium are produced. Both these forms of plants relied on water or at least damp conditions to allow transport of the spermatozoid to the egg.
The earliest gymnosperms appear in the very latest Devonian and rapidly become diverse and important during the Carboniferous. The angiosperms did not appear untill the early Cretaceous and diversified rapidly from the mid Cretaceous. The fact that spores and pollen are normally retrieved from their host sediments as disjunct entities, separate from the original parent plant means that their natural affinities are often obscure.
The free sporing plants including the Bryophyta e. The important feature of homospory in terms of the fossil record is the four fold division involved in spore production, this takes the form of either a tetrahedra which gives a trilete spore or a tetragon which gives a monolete spore. The trilete and monolete marks imparted on the individual spores are the marks where each of the spore tetrad once abutted each other.
Classification of pollen, like that of spores is based on the morphological trends observed among various groups of fossils which may be primarily but not entirely reflections of evolution within the groups of plants which produced the pollen. It should also be remembered that higher plants have charcteristics of reproduction which permit them to utilise modes of evolution unavailable to animals. Because of their relatively simple genetic systems plants may utilise hybridisation and self fertilisation.
The early gymnosperms produce prepollen, differentiated from true pollen by germination from the proximal rather than the distal side. Recent gymnosperms may produce very distinctive saccate pollen, i.
The angiosperms produce pollen with the greatest morphological variation, but typicaly with either a tricolpate or monosulcate form. See Biology below. While botanical information from them may be limited, fossil spores and pollen have proved exceptionally useful as biostratigraphic indices. They are particularly valuable in freshwater environments, in evaporitic deposits and situations where marine and freshwater facies interdigitate.
Spores, in the broadest sense, are produced in the life cycles of so called "lower plants" or cryptograms, comprising algae, fungi, bacteria and the extensive array of seedless metaphytes.
The extine contains one or more thin places known as the germ pores through which the intine grows out to form the pollen tube. The pollen tube elongates trough the gynoecium tissues carrying two male gametes in it. Pollen tube grows down and enters the ovule through the micropyle. Then the apex of the pollen tube degrades and the two male nuclei are released in to the ovule. Double fertilization takes place by the fusion of the one male nucleus with the egg cell nucleus, giving rise to the diploid zygote, and fusion of the other male nucleus with the diploid secondary nucleus giving rise to the triploid primary endosperm nucleus.
In other words, all pollens are spores, but not all spores are pollens. Your email address will not be published. Leave a Reply Cancel reply Your email address will not be published. What is the difference between Spores and Pollens? The answer is no, because ferns are spore-bearing plants. While seed-bearing plants like corn make pollen, spores are reproductive structures of seedless vascular plants like ferns.
There are several differences between spores and pollen grains. One of the most important differences is the fact that spores are unicellular and pollen grains are multicellular.
To define "spore," it's essential to understand how spore-bearing plants reproduce. Ferns, horsetails and club mosses are some of the types of seedless vascular plants that make spores.
The term "vascular plants" refers to the fact that these plants have xylem and phloem, vascular tissues that move water and nutrients around the plant structure. Mosses, liverworts and hornworts are examples of plants that do not have vascular tissues.
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