- Organogenesis is a word which is derived from two Greek word oregano and genesis means organ and genesis means synthesis.
- Organogenesis can be designed as the process of formation of specific organ in a plant or animal involving morphogenesis and differentiation.
- It’s a series of organised in a targeted process that transfers amorphous mass of cell into a complete organ contributing to the morphology of the organism.
- A plant contain many organ like meristem, phloem ,epidermis, cortex are consisting of structural unit called cell.
- In vitro condition when a plant cell which has the capability to produce the whole plant undergoes certain laboretical experiment to generate various organs.
- This in vitro generation of plant organ which give rise to a new individual plant is known as organogenesis in plants.
- Organogenesis is broadly classified into two types one is indirect organogenesis and another one is direct organogenesis.
Types of organogenesis
- Organogenesis employees development of organ structure usually from undifferentiated cells but also from preciously specialised cell would not normally give rise to organised multicellular growth.
- In plant tissue culture on differentiated tissue is referred to as callus.
- Although callus contain meristematic nodules that may not be obvious to naked eye but which never develop for their unless suitable condition are supplied.
- Development of organised structure may follow one of the three paths:-
- shoot regeneration based on unipolar structure with the shoot apical meristem.
- Root regeneration essentially and unipolar based on the concept with root apical meristem.
- Somatic organogenesis in which there is a epix structure.
- In vitro differentiation however can be of two types:-
- An understanding of the mechanism underlying regeneration of whole plant or parts of plant from cell.
- The direct of differentiation would be influenced by the ratio of exogenous supplied growth regulators auxin and cytokinin.
- It was observed in tobacco stain culture that a high ratio of auxin to cytokinin lead to the development of shoots.
- It is now obvious that the group of growth regulators play important role in unlocking totipotency expression to plant differentiation and callus formation occurs naturally in response involve auxin and cytokinin and some to be biological trigger for the plant regeneration of somatic cell.
- However sustainedcolours growth in vitro requires addition of one or more growth regulators prior to the chemical characterization of IAA in 1934.
- Auxins is essential for a differentiation and commonly 2, 4 dichlorophenoxyacetic acetic acid is used to promoted callus cytokinin enhance this process.
- In tissue with the high endogenous level oxygen culture of explant on a medium is the only growth regulator may lead to development of shoot with a very little callus.
- Not all living cell not respond to auxin and this is particularly true for much your cell of grasses without differentiation it is not possible to move the next page of totipotency expression plant regeneration.
- The first example of a single isolated cell dividing directly to produce an embryo recorded in 1970 in a suspension culture.
- Protoplast capable of undergoing a division is quiscent cell continuous present auxins can inhibit organised outgrowth.
- This is typical sequential function of singular hormone through a developmental progression.
- Cytokinin promote outgrowth of roots that are hormone kept out low concentration with root generation.
- Thus the formation of shoot from callus in presence of the growth hormone cytokinin is known as shoot or indirect organogenesis.
- It bypass the need callus formation of somatic embryos.
- It produce from cell which are already in emberyogenically component while they were part of original differentiated tissue.
- This tree in cryogenic cells appear only to required favourable condition to allow release into cell division and expression of embryogenesis search cell tends to the expressive than those involved in indirect organogenesis.
- This do not seem to require the more oxygen to initiate the division.
- Indeed the cells may never left the cell cycle and growth regulator applications has some subtle functions.
- Used as regeneration of whole plant for culture.
- Used as mode of mass production of plant varieties.
Factors influencing organogenesis
- Size of explant:-Organogenesis directly depends on the size of explant.
- Here small group of homogenous tissues are taken from the epidermal and some epidermal layer that could directly or indirectly give rise to plant organ.
Sources of explant
- This is important because it determine the potential of organogenesis.
Age of explant:
- The physiological age of explained often plays important role in organogentic phenomenon.
- The seasonal variation is the factor which exercise the organ formation.
- Oxygen gradient in tissue culture influence and organ formation like some culture shoot formation takes place when the gradient of variable oxygen inside the culture vessel is reduced during root formation it requires a high level of O2.
Intensity and quality of light
- This is the most important factor in the formation of organogenesis and The spectrum of light on organogenesis reveals that blue reason of the spectrum promote shoot formation and red like root formation.
- Most tissue culture are grown successfully at temperature around 25 degree Celsius but in a number of species the optimum temperature may be lower than 15 degree Celsius and for tropical spaces require a higher temperature of 25 degree Celsius.
Lateral root organogenesis:-