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The flower is the characteristic structure concerned with sexual reproduction in flowering plants (angiosperms). Flowers vary enormously in their structure (morphology). A perfect flower, like that of Ranunculus glaberrimus shown in the figure, has a calyx of outer sepals and a corolla of inner petals and both male and female sex organs.
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes , resulting in offspring genetically different from either parent.
Sexual selection through female choice is perhaps a more difficult concept to apply to plants. There is evidence that females (or the female function of hermaphrodites) exercise choice, especially during fertilization. [2] These two mechanisms are the main driving forces of sexual selection in flowering plants.
ABC model of flower development guided by three groups of homeotic genes.. The ABC model of flower development is a scientific model of the process by which flowering plants produce a pattern of gene expression in meristems that leads to the appearance of an organ oriented towards sexual reproduction, a flower.
In 2013, flowers dating from the Cretaceous (100 million years before present) were found encased in amber, the oldest evidence of sexual reproduction in a flowering plant. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma.
Sexual systems play a key role in genetic variation and reproductive success, and may also have led to the origin or extinction of certain species. [4] In flowering plants and animals, sexual reproduction involves meiosis, an adaptive process for repairing damage in the germline DNA transmitted to progeny. [5]
Meiosis in flowering plants provides a direct mechanism for repairing DNA through genetic recombination in reproductive tissues. [75] Sexual reproduction appears to be required for maintaining long-term genomic integrity and only infrequent combinations of extrinsic and intrinsic factors permit shifts to asexuality. [75]
A far more rudimentary form of double fertilization occurs in the sexual reproduction of an order of gymnosperms commonly known as Gnetales. [3] Specifically, this event has been documented in both Ephedra and Gnetum, a subset of gnetophytes. [7] In Ephedra nevadensis, a single binucleate sperm cell is deposited into the egg cell. Following the ...