Table Comparing Apogamy and Apospory Processes in Plants
Apomixis is the process of formation of the plant from a seed without fertilization or normal sexual reproduction. The word 'Apomixis' is derived from two Greek words- "Apo" means "without" and "mixes" means "the act of mixing". It is a type of asexual reproduction, but it does not come entirely under the category of "normal asexual reproduction", which involves propagation from cuttings or leaves. Replacement of the flower by bulbs and replacement of the seed by a plantlet can be considered as types of apomixis. Apospory is the most common type of apomixis in higher plants.
What are Apogamy and Apospory?
Apogamy and apospory are two types of asexual reproduction that occur in the plant kingdom. In contrast, both sexual and asexual reproduction occur during fertilization. Apospory is a specific type of Apogamy in which new plants are formed without fertilization but using the diploid cells of an existing plant. This process does not create any new genetic variation in the species.
Apogamy is a unique process of asexual reproduction in ferns, in which the development of haploid sporophyte(n) occurs from a haploid gametophyte(n) without the fusion of gametes. Heinrich Anton de Bary termed this type of asexual reproduction in ferns as Apogamy in the year 1878. In the year 1874, Farlow discovered the natural occurrence of Apogamy in Pteris cretica. Dryopteris, Pteris, Osmunda, Adiantum are the ferns in which Apogamy occurs naturally.
Apospory is the process of formation of the diploid gametophyte (2n) from the vegetative cells of the sporophyte (2n), without meiosis and formation of spores. It was first discovered in the year 1884 by Druery in the plant Athyrium foemina var. Clarissa Jones. The prosperous gametophyte that has formed in this variety developed from its sporangium stalk and head. Pteris aquiline, Asplenium dimorphism, Osmunda javanica are the plants in which apospory occurs naturally.
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The Key Difference Between Apospory and Apogamy
The major differences between apospory and Apogamy are tabulated below.
Causes of Apogamy and Apospory
Causes of Apogamy
The chances of occurrence of Apogamy are high in those plants whose prothallus have aged.
When the gametophyte fails to produce gametes, there will be fewer chances for fusion. Hence, Apogamy will occur in such a situation where the failure of sex organ formation occurs.
Apogamy happens in those situations when the plants fail to carry out normal fertilization (sexual reproduction), either due to certain abnormal physiological conditions or environmental conditions.
If the prothallus of ferns or pteridophytes grows under high temperatures and bright light, their sexual organs cannot grow normally. Hence, Apogamy occurs in that particular situation.
When there are water and nutrition deficiencies in the plant due to high temperature, under those conditions, the plant carries out Apogamy.
Causes of Apospory
Apospory occurs in those pteridophytes who suffer from the deficiency of mineral nutrition due to the lack of minerals in the soil.
If the leaves of pteridophyte develop under dim light, chances of occurrence of apospory become high.
Similarities Between Apogamy and Apospory
Asexual reproduction takes place during both Apogamy and apospory.
Both of them take place in plants.
The gametophyte and sporophyte share the same ploidy level in both phenomena.
Both of them take place mainly in bryophytes.
The formation of gametes does not occur in Apogamy and apospory.
Both of them participate in the alternation of generation (alteration of a sexual phase, i.e., gametophyte and an asexual phase, i.e., sporophyte) in the life cycle of an organism.
Did You Know?
Apospory and Apogamy can be induced artificially in a laboratory with the help of hormones. Lycopodium and equisetum are the plants in which Apogamy can be induced artificially. The artificial induction of apospory was first reported in Pteridium. Ceratopteris richardii is a model fern that does not carry out asexual reproduction naturally. Still, Apogamy and apospory can be induced in it in the laboratory by using specific culture conditions.
FAQs on Apogamy vs Apospory: What Sets Them Apart in Biology?
1. What is apogamy in the context of plant reproduction?
Apogamy is a type of asexual reproduction where a sporophyte (the diploid plant body) develops directly from a cell of the gametophyte (the haploid structure) without the fusion of gametes (fertilisation). The cell that develops into the sporophyte is any cell other than the egg cell, such as a synergid or an antipodal cell. The resulting sporophyte is typically haploid (n).
2. What is meant by apospory in plants?
Apospory is a form of apomixis where a gametophyte develops directly from a vegetative cell of the sporophyte, such as a cell from the nucellus or integument in flowering plants, completely bypassing the process of meiosis and spore formation. Because it originates from a diploid (2n) cell without reduction division, the resulting gametophyte is also diploid (2n).
3. What is the primary difference between apogamy and apospory?
The primary difference lies in the origin and ploidy of the resulting plant structure. In apogamy, a sporophyte (usually haploid) arises from a gametophyte. In apospory, a gametophyte (usually diploid) arises from a sporophyte. Essentially, they are opposite processes in terms of the generational shift.
4. How can the key differences between apogamy and apospory be summarised?
Here are the key distinctions between apogamy and apospory:
- Definition: Apogamy is the development of a sporophyte from a gametophyte cell without fertilisation. Apospory is the development of a gametophyte from a sporophyte cell without meiosis.
- Origin: In apogamy, the new plant body originates from a gametophytic cell (e.g., synergid). In apospory, it originates from a sporophytic vegetative cell (e.g., nucellus).
- Process Bypassed: Apogamy bypasses fertilisation. Apospory bypasses meiosis.
- Resulting Ploidy: Apogamy typically results in a haploid (n) sporophyte. Apospory results in a diploid (2n) gametophyte.
5. How do the chromosome numbers (ploidy) of the resulting plants differ in apogamy and apospory?
The ploidy level is a critical distinguishing factor. In apogamy, a haploid (n) gametophyte produces a haploid (n) sporophyte because fertilisation, which would have restored the diploid number, is skipped. In apospory, a diploid (2n) sporophyte cell directly develops into a diploid (2n) gametophyte because meiosis, the process of halving chromosome numbers, is bypassed.
6. Why are apogamy and apospory commonly studied in ferns (Pteridophytes)?
These phenomena are commonly observed and studied in ferns because their life cycle features distinct, free-living gametophyte (prothallus) and sporophyte (the fern plant) generations. This clear separation makes it easier to identify when one generation arises directly from the other without the normal reproductive steps. For example, a new fern plant (sporophyte) can be seen budding directly from the prothallus (gametophyte) in apogamy.
7. How is apogamy fundamentally different from parthenogenesis?
While both are forms of asexual reproduction, their cellular origins are different. Parthenogenesis is specifically the development of an embryo from an unfertilised egg cell. In contrast, apogamy is the development of an embryo from any other cell of the gametophyte, such as synergids or antipodal cells, but not the egg cell. Parthenogenesis is development from the female gamete; apogamy is development from a non-gamete cell of the gametophyte.
8. What is the agricultural significance of understanding apogamy and apospory?
Understanding these processes is crucial for modern agriculture, particularly in plant breeding. Both are forms of apomixis, which allows for the production of seeds without fertilisation. This can be used to create clonal seeds of hybrid plants. It helps preserve desirable traits like high yield or disease resistance (hybrid vigour) across generations, which would normally be lost through sexual reproduction and genetic segregation.
