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In a willow (like all seed plants) the zygote first develops into an embryo microsporophyte within the ovule (a megasporangium enclosed in one or more protective layers of tissue known as integument). At maturity, these structures become the seed. Later the seed is shed, germinates and grows into a mature tree.
In both gymnosperms and angiosperms, the young plant contained in the seed, begins as a developing egg-cell formed after fertilization (sometimes without fertilization in a process called apomixis) and becomes a plant embryo. This embryonic condition also occurs in the buds that form on stems. The buds have tissue that has differentiated but ...
The embryophytes (/ ˈ ɛ m b r i ə ˌ f aɪ t s /) are a clade of plants, also known as Embryophyta (/ ˌ ɛ m b r i ˈ ɒ f ə t ə,-oʊ ˈ f aɪ t ə /) or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth 's dry lands and wetlands .
Mature egg cells are produced by mitotic divisions, and these cells directly develop into embryos. In flowering plants, cells of the gametophyte can undergo this process. The offspring produced by apomictic parthenogenesis are full clones of their mother, as in aphids. [citation needed]
In genetics, a maternal effect occurs when the phenotype of an organism is determined by the genotype of its mother. [1] For example, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation.
In animals, egg cells are also known as ova (singular ovum, from the Latin word ovum meaning 'egg'). [7] The term ovule in animals is used for the young ovum of an animal. In vertebrates, ova are produced by female gonads (sex glands) called ovaries. A number of ova are present at birth in mammals and mature via oogenesis.
Specimens of juvenile plants may look so completely different from adult plants of the same species that egg-laying insects do not recognize the plant as food for their young. The transition from early to late growth forms is sometimes called vegetative phase change .
Revertant somatic mosaicism is a rare recombination event with a spontaneous correction of a mutant, pathogenic allele. [19] In revertant mosaicism, the healthy tissue formed by mitotic recombination can outcompete the original, surrounding mutant cells in tissues such as blood and epithelia that regenerate often. [ 19 ]