– Via dehydration & inactivates many receptors
At maturation, arrest occurs– embryo inactive and seed dehydrated
From: Late seed maturation: drying without dying
J Exp Bot. 2016;68(4):827-841. doi:10.1093/jxb/erw363
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Relative importance of the three phases of seed development.
Data are taken from the literature showing the evolution of fresh and dry weight and water content during seed development.
The switch from embryogenesis to seed filling is defined as the onset of the increase in dry weight. Late seed maturation starts when seed filling ceases. Seed development is considered to be terminated when seed moisture content is less than 20%. Data are from Ellis et al., 1993 (1); Bartels et al., 1988 (2); Hay et al., 2010 (3); Welbaum and Bradford, 1988 (4); Zanakis et al.,
2010 (3); Welbaum and Bradford, 1988 (4); Zanakis et al., 1994 (5); Sinniah et al., 1998 (6); Hay and Probert,
1995 (7); Chatelain et al., 2012 (8); Sanhewe and Ellis, 1996 (9); Gray et al., 1988 (10); Kermode and Bewley 1985 (11); Guillon et al., 2012 (12); Ellis and Pieta Filho, 1992 (13); Demir and Ellis, 1992(14); Jayasuriya et al., 2007 (15); Galau et al., 1987 (16); Rodríguez et al.,
2013 (17); Baud et al., 2002 (18); Fischer et al., 1988 (19); Still and Bradford, 1998 (20).
Main physiological and biochemical events related to seed filling and the acquisition of longevity during late seed maturation are
overlapping in Medicago truncatula (above) in contrast to Arabidopsis thaliana (below). The broken line indicates the loss of water during development. DT, desiccation tolerance; EMB, embryogenesis; P50, half-life of viability loss during storage; RFO, raffinose family
half-life of viability loss during storage; RFO, raffinose family oligosaccharide content. Adapted from Righetti et al.(2015).
Parthenocarpy and Apomixis
Plants produce fruits and seeds following pollination and fertilization.
But, there are other ways fruits and seeds are produced.
Parthenocarpy is the formation or development of fruit without fertilization.
Apomixis, on the other hand, is the formation of seeds without Apomixis, on the other hand, is the formation of seeds without fertilization.
The difference between the fruits developed naturally and through parthenocarpy is that the fruits formed through parthenocarpy are seedless.
They are known as seedless.
Parthenocarpy is a form of asexual reproduction seen in flowering plants.
It is found naturally in plants like banana and can also be induced artificially using growth regulators.
Parthenocarpy is being increasingly used to produce seedless fruit varieties today because of the high quality and consistency in the yield.
yield.
In parthenocarpy, the ovary is stimulated even without pollination and thus fruit development begins without fertilization.
This is common in plants that have no ovary or plants that have lost their ability to reproduce sexually due to a mutation.
Apomixis
While parthenocarpy is the formation of fruit without fertilization, apomixis is the formation of seeds without fertilization.
In a natural flow of biological processes, pollination is the first step in the formation of a fruit and seed.
The subsequent steps include cell divisions and fertilization.
But, in this case, there is no meiotic division and fertilization of the But, in this case, there is no meiotic division and fertilization of the gametes to form a zygote.
The entire process is cut short and seed formation occurs by the way of apomixis.
It can be of two types:
Sporophytic – In this type, apomixis occurs from the diploid sporophyte Gametophytic – In this type, apomixis occurs from the haploid
gametophyte
Since apomixis involves the formation of seeds without syngamy, all the seeds are genetically similar. Therefore, it can be used in vegetative propagation.
Similarities and Differences
We have understood about parthenocarpy and apomixis individually, but let us understand the similarities and difference between the two.
Similarities
In both apomixis and parthenocarpy, there is no fertilization involved. So, both produce offsprings similar to parents. In both cases, there is no chance of diversity in genes.
Since both the types of phenomenon do not involve fertilization, they are both used as asexual means or vegetative propagation methods. Though both methods used as asexual means or vegetative propagation methods. Though both methods are asexual, they still use the sexual organs of the plant- the ovary and the ovules.
Differences
Both apomixis and parthenocarpy are asexual modes of reproduction, apomixis is the formation of seeds whereas parthenocarpy is the formation of fruits without fertilization.
Apomixis produces genetically identical mother cells whereas parthenocarpy produces genetically identical offsprings.
Apomixis is seen in angiosperms and gymnosperms but parthenocarpy is seen in plants and animals. Parthenocarpy in animals is called as parthenogenesis.
Apomiksis adalah suatu bentuk reproduksi non-seksual pada tumbuhan melalui biji.
Pada apomiksis, kecambah(-kecambah) muncul dari biji tetapi bukan berasal dari embrio (lembaga), melainkan dari jaringan maternal (asal tetua betina).
Akibatnya, secara genetik tumbuhan-tumbuhan baru yang muncul adalah identik dengan tetua betinanya (klon).
Walaupun demikian, sekarang ditemukan kasus "apomiksis jantan"
yang terjadi pada sejenis sipres (Cupressus dupreziana).[1]
Kasus apomiksis banyak terjadi pada tumbuhan tropika.
Beberapa varietas manggis dan kerabatnya (marga Garcinia) dapat memperbanyak hanya melalui apomiksis.
Contoh tumbuhan lain yang diketahui memiliki perilaku ini adalah berbagai jenis jeruk dan duku.
The endosperm of orchids is nuclear. In certain cases double fertilization does not occur and the endosperm does not form. The degree of endosperm development and degeneration differs between taxa. The data of some authors indicate that endosperm reduction in orchids is indicate that endosperm reduction in orchids is directly dependent on the degree of embryo reduction and/or on the degree of suspensor development (Teryokhin and Kamelina, 1969, 1972; Teryokhin, 1977).