Plant Tissue Culture Flashcards
PLANT TISSUE CULTURE
Plant tissue cultureis a collection of techniques used to grow plant cells, tissues or organs under sterile conditions on a nutrient culture medium of known composition
Plant tissue culture relies on the fact that plant cells have the ability to regenerate into a whole plant
Single cells, plant cells without cell walls (protoplast), pieces of leaves, stems or roots can be used to generate a new plant on culture media given the required nutrients andplant hormones
Totipotency
Ex plant
Callus
Totipotency: the ability of a single cell to divide and produce all the differentiated cell of an organism
Ex plant: a piece ofplant tissueplaced intotissue culture
Callus : a mass of undifferentiated cells,cultivated on gel media that develops during tissue cultureof plant parts
1…………………….. is thein vitroaseptic culture of cells, tissues, organs or whole plant under controlled nutritional and environmental conditions to produce the clones of plants
1.Tissue culture
The resultant clones are true-to type of the selected genotype
The controlled conditions provide the culture an environment conducive for their growth and multiplication
These conditions include proper supply of nutrients, pH medium, adequate temperature and proper gaseous and liquid environment.
common types of tissue culture
Anther culture and Embryo culture.
Anther culture is a tissue culture method used to develop improved varieties in a short time
Pollen within an anther contains half dose of the genome (haploid) which spontaneously double (diploid) during culture
In some species, however,** colchicine** treatment is necessary to induce doubling
Doubling of the genome will allow the expression of recessive traits which were suppressed, masked or undetected in routine plant breeding
Anthers are placed in a special medium, and immature pollen within the anther divide and produce a mass of dividing cells (callus)
Healthy calli (plural of callus) are picked and placed in another medium to produce shoots and roots (regeneration)
Stable plantlets are allowed to grow and mature in the greenhouse
Plant breeders can then select the desired plants from among the regenerated plants.
This technology has been employed in the successful development of doubled haploid lines or varieties of rice, wheat, sorghum, barley, and other field crops
Embryo rescue involves the culture of immature embryos of plants in a special medium to prevent abortion of the young embryo and to support its germination
This is used routinely in breeding parental lines having different or incompatible genome such as in introducing important traits of wild relatives into cultivated crops.
Embryo culture
Embryo culture is used to grow embryos from seeds and ovules in a nutrient medium
The plant develops directly from the embryo or indirectly through the formation of callus and then subsequent formation of shoots and roots
The development of a new rice plant type for West Africa (NERICA – New Rice for Africa) was a result of wide crosses between the Asian Oryza sativa and the African rice Oryza glaberrima
It employs embryo rescue in the initial breeding and in the successive back crossing work followed by anther culture to stabilize the breeding lines.
Micro-propagation
Micro-propagation is a tissue culture method developed for the production of disease-free, high quality planting material and for rapid production of many uniform plants
Actively-dividing young cells (meristem) are placed in a special medium and treated with **plant hormones **to produce many similar sister plantlets
Since the meristem divides faster than disease-causing virus, clean materials are propagated and hundreds of uniform plantlets are produced in a short time.
Through micro-propagation, it is now possible to provide clean and uniform planting materials in plantations crops (oil palm, banana), field crops (eggplant, tomato), root crops (cassava, potato) and many ornamental plants such as orchids
Micro-propagated plants are found to establish more quickly, grow more vigorously and taller, have a shorter and more uniform production cycle, and produce higher yields than conventional propagules.
Stages in micro-propagation
Micro-propagation starts with the selection of plant tissues (ex plant) from a healthy, vigorous mother plant
Any part of the plant (leaf, apical meristem, bud and root) can be used as ex plant
There are usually four stages:
Stage 0: Preparation of donor plant
Any plant tissue can be introducedin vitro
To enhance the probability of success, the mother plant should beex vitrocultivated under optimal conditions
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Stage I: Initiation stage**
In this stage an ex plant is surface sterilized and transferred into nutrient medium
The cultures are incubated in growth chamber either under light or dark conditions according to the method of propagation.
Stage II: Multiplication stage
The aim of this phase is to increase the number of propagules
The number of propagules is multiplied by repeated subcultures until the desired (or planned) number of plants is attained
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Stage III: Rooting stage**
The rooting stage may occur simultaneously in the same culture media used for multiplication of the explants
However, in some cases it is necessary to change media, including nutritional modification and growth regulator composition to induce rooting and the development of strong root growth.
Stage IV: Acclimatization Stage
At this stage, thein vitroplants are weaned and hardened
Hardening is done gradually from high to low humidity and from low light intensity to high light intensity
The plants are then transferred to an appropriate substrate (sand, peat, compost etc.) and gradually hardened under greenhouse.
Plant Tissue Culture Media
Plant tissue culture media generally contain these components: macronutrients, micronutrients, vitamins, amino acids or nitrogen supplements, sources of carbon, growth regulators and solidifying agents
Macronutrients: The essential elements include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S)
Micronutrients :The essential micronutrients include iron (Fe), manganese (Mn), zinc (Zn), boron (B), copper (Cu) and molybdenum (Mo)
Carbon and energy sources : Besides sucrose, other carbohydrates such as lactose, galactose, maltose and starchare also used
Vitamins : The vitamins most used in the cell and tissue culture media include: thiamin (B1), nicotinic acid and pyridoxine (B6)
Amino acids : The required amino acids for optimal growth are usually synthesized by most plants, however, the addition of certain amino acids is important for establishing cultures of cells and protoplasts
Solidifying agents : There are a number of gelling agents such as agar, agarose and gellan gum.
Advantages of Tissue Culture
The production of exact copies of plants that produce particularly good flowers, fruits, or have other desirable traits.
To quickly produce mature plants.
The production of multiples of plants in the absence of seeds or necessary pollinators to produce seeds.
The regeneration of whole plants from plant cells that have been genetically modified.
The production of plants in sterile containers that allows them to be moved with greatly reduced chances of transmitting diseases, pests, and pathogens.
Advantages of Tissue Culture
The production of exact copies of plants that produce particularly good flowers, fruits, or have other desirable traits.
To quickly produce mature plants.
The production of multiples of plants in the absence of seeds or necessary pollinators to produce seeds.
The regeneration of whole plants from plant cells that have been genetically modified.
The production of plants in sterile containers that allows them to be moved with greatly reduced chances of transmitting diseases, pests, and pathogens.
The production of plants from seeds that otherwise have very low chances of germinating and growing, example: OrchidsandNepenthes
To clear particular plants of viral and other infections and to quickly multiply these plants as ‘cleaned stock’ for horticulture and agriculture.
