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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 ...
Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and microsporangia. A megaspore often (but not always) develops at the expense of the other three cells resulting from meiosis, which abort.
The embryo sporophyte develops by cell division of the zygote within the female sex organ or archegonium, and in its early development is therefore nurtured by the gametophyte. [1] Because this embryo-nurturing feature of the life cycle is common to all land plants they are known collectively as the embryophytes .
There is debate as to whether endospory or heterospory evolved first. Some debate centers upon the requirement of endospory to develop before heterospory. [2] Endospory is assumed to follow heterospory but it has been suggested that without endospory, early plant species dependency on water fertilization and environmental impacts on gametophytic gene expression would have reduced the chances ...
During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). [1] Angiosperms exhibit three patterns of megasporogenesis: monosporic, bisporic, and tetrasporic, also known as the Polygonum type, the Alisma type, and the Drusa type ...
The sporophyll of a fern. It is a fertile leaf bearing reproductive structures. In botany, a sporophyll is a leaf that bears sporangia.Both microphylls and megaphylls can be sporophylls.
An organelle present in plant cells which contains chlorophyll. chlorosis An abnormal lack or paleness of color in a normally green organ. cilia. sing. cilium; adj. ciliate. Very small hairs or hair-like protrusions more or less confined to the margin s of an organ, as with eyelashes; in motile cells, minute, hair-like protrusions which aid ...
In normal cells, growth is controlled by contact inhibition in which contact with neighboring cells causes a stunt in cell growth. Contact inhibition is thought to be mediated by cadherins, proteins that play an important role in cell adhesion. This inhibition prevents cells from piling up on top of one another and forming mounds.