Dunaliella salina - Overview

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                 Dunaliella salina Dunaliella salina is a unicellular microalgae belong to division Chlorophyta . It is found in salinity environments such as salted brines, salt evaporation ponds, and hypersaline lakes  .It is able to tolerate varying NaCl concentrations, ranging from 0.2% to approximately 35% . Thus, Dunaliella salina is a hyper-halotolerant organism found in high densities in saline lakes.  The ability to tolerate high salt concentrations is advantageous, since competition is minimal in high salt concentration areas.  How D.salina   tolerate high salt concentration? D. salina has adapted to survive in high salinity environments by accumulating glycerol to balance osmotic pressure. Note :  D. salina is also adapted to solar radiation using β-carotene to protect against ionizing energy.                 Red Colour of Salt Brines  Dunaliella salina...
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Apomixis - Definition, Types,Importance

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                  Apomixis

Definition: Formation of seeds without the fertilisation is called apomixis.

 *Term given by Winkler.  It is a specialised asexual reproduction that mimics sexual reproduction.

*Common in Asteraceae family,in grasses and 35other family.

                Types of Apomixis

***Adventitious Embryony /Sporophytic Budding: 
When diploid cells of Sporophytic tissues like nucellus and integument start to divide and develop into embryo. From nucellus cells ,nucellar embryo is formed. From integument cells , integumentary embryo is formed. Examples : Citrus, Mango 🥭,Opuntia.

***Apogamy: When Sporophyte develop directly from the gametophyte without fertilization (meiosis occur),the phenomenon called apogamy.Such sporophytes are haploid and non-viable(Non-recurrent Agamospermy).

***Parthenogenesis: The phenomenon in which egg develop directly into an embryo without fertilizing with sperm.Also called as Virgin birth.

***Diplospory and Apospory:
In apospory,Nucellus(Sporophyte)~gametohyte.Hence, apospory is the phenomenon of development of gametophyte directly from the Sporophyte without meiosis.

*Androgenesis: It is the formation of Sporophyte from the male gametophyte on artificial medium. Most commonly found in Solanaceae  and   Poaceae .In androgenesis, immature pollen grains are induced to follow the Sporophytic mode of development by various physical and chemical stimuli.

**Recurrent Agamospermy:
Development of diploid (2n) embryo sac. Example: Allium, Pear🍐,Apple 🍎,

Importance of Apomixis

*Easy maintenance of pure lines.
*Synchronous flowering and maturity of the crop.
*Fixation of heterosis in the hybrids.
*Pollen dispersal is not relevant during hybrid seed production.
*Minimal isolation distance in hybrid seed production.
*Nucleus seed of hybrid varieties is conventional maintained as the hybrid varieties.

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