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Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore , is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isospory independently in several plant groups: the clubmosses , the ferns including the arborescent ...
Diagram showing the alternation of generations between a diploid sporophyte (bottom) and a haploid gametophyte (top) A sporophyte (/ ˈ s p ɔːr. ə ˌ f aɪ t /) is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase.
In gymnosperms and flowering plants, the megaspore is produced inside the nucellus of the ovule.During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). [1]
Alternation between a multicellular diploid and a multicellular haploid generation is never encountered in animals. [33] In some animals, there is an alternation between parthenogenic and sexually reproductive phases , for instance in salps and doliolids (class Thaliacea). Both phases are diploid.
There is a marked difference in shape between the first dark green "seed leaves" and the lighter second pair of leaves. The organs and tissues produced by a young plant, such as a seedling, are often different from those that are produced by the same plant when it is older. This phenomenon is known as juvenility or heteroblasty. For example ...
[11] [10] One of these cells is typically a germ cell and other cells may consist of a single tube cell which grows to form the pollen tube, sterile cells, and/or prothallial cells which are both vegetative cells without an essential reproductive function. [10] After pollination is successful, the male gametophyte continues to develop.
The etymology of the word "morphology" is from the Ancient Greek μορφή (morphḗ), meaning "form", and λόγος (lógos), meaning "word, study, research". [2] [3]While the concept of form in biology, opposed to function, dates back to Aristotle (see Aristotle's biology), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist ...
A rarely used term describing substantial differences between the overall structure of an inflorescence and that of its individual branches, e.g. the bottlebrush multiple-flower head of members of the genus Callistemon. connate Fused to another organ (or organs) of the same kind, e.g. petal s in a gamopetalous corolla tube. Compare adnate ...