Tissue Culture Questions in English

(B) In plant tissue culture,$Callus$ is defined as an unorganized,undifferentiated mass of proliferating cells. It typically develops from explants (pieces of plant tissue) when placed on a nutrient medium under controlled conditions. It can also form in nature as an irregular growth of cells at the site of a plant injury to protect the wound.

(B) Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism.
Examples include spores and zygotes.
This inherent capacity allows a cell to regenerate a new whole organism under appropriate conditions.

(B) dormant callus refers to a callus that has become inactive or permanent in its growth state. In plant tissue culture,callus is an unorganized mass of proliferating cells. When this growth stops or enters a state of quiescence due to environmental factors or nutrient depletion,it is referred to as a permanent or dormant callus.

(C) $EDTA$ (Ethylenediaminetetraacetic acid) acts as a chelating agent and is often used in tissue culture media to maintain the stability of the medium by acting as a buffer. It helps in maintaining the $pH$ of the culture medium,which is essential for the optimal growth of plant tissues.

(C) In plant tissue culture,$2,4-D$ ($2,4-$dichlorophenoxyacetic acid) is the most widely used synthetic auxin.
It is highly effective in inducing callus formation and promoting cell division in both callus and suspension cultures due to its stability and potent physiological activity.

(B) In plant tissue culture,plant growth regulators are essential for the growth and differentiation of callus. $Kinetin$ is a type of cytokinin,which is a class of plant hormones that promote cell division $(cytokinesis)$ and organogenesis. Therefore,$Kinetin$ is commonly added to the culture medium to induce shoot formation and promote growth.

(B) In plant tissue culture,the balance between auxin and cytokinin is crucial for organogenesis. Among the options provided,$Kinetin$ (a type of cytokinin) is considered indispensable because it promotes cell division (cytokinesis) and is essential for the formation of shoots in callus cultures.

(C) In plant tissue culture,the differentiation of callus into organs is regulated by the ratio of auxins (like $IAA$) to cytokinins (like kinetin).
When the concentration of cytokinin (kinetin) is higher than that of auxin $(IAA)$,it promotes the development of shoots (caulogenesis).
Conversely,a higher concentration of auxin relative to cytokinin promotes root development (rhizogenesis).
Therefore,increasing the ratio of kinetin to $IAA$ will lead to shoot initiation.

(D) . Nerve cells cannot be grown under tissue culture conditions because they are highly specialized cells that have lost the power of cell division. Once mature,neurons do not undergo mitosis,making them unsuitable for standard tissue culture propagation.

(B) Micropropagation is a tissue culture technique used to produce large numbers of genetically identical plants (clones) from a small piece of plant tissue (explant) in a sterile culture medium.
This method is widely used in agriculture and horticulture for the rapid multiplication of economically important plants.

(B) The correct answer is $B$.
Plant tissue culture media require specific nutrients for the growth of explants.
Coconut milk, derived from the endosperm of $Cocos nucifera$ (coconut), is widely used as a natural source of growth regulators (specifically cytokinins), vitamins, and amino acids in plant tissue culture media to promote cell division and growth.

(D) haploid callus is derived from cells that contain only one set of chromosomes $(n)$.
In plants,the only cells that are naturally haploid are the gametophytes,such as pollen grains (microspores) or embryo sacs (megaspores).
By culturing pollen grains (microspore culture) on a suitable nutrient medium,the cells undergo division to form a mass of undifferentiated haploid cells known as a haploid callus.
Embryos,leaf tissues,and stigmas are diploid $(2n)$ structures and would result in a diploid callus.

(D) The formation of an embryoid from a pollen grain (microspore) in a tissue culture medium is a classic example of cellular totipotency.
Cellular totipotency is the ability of a single plant cell to divide and differentiate into all the specialized cells of a mature plant.
In this process,the haploid pollen grain is induced to undergo embryogenesis,forming a haploid embryo (embryoid) instead of developing into a male gametophyte.
This phenomenon demonstrates that even specialized cells like pollen grains retain the genetic potential to regenerate an entire organism under appropriate in vitro conditions.

(B) Micropropagation is a technique of plant tissue culture used to produce large numbers of progeny plants from a small explant.
In the case of carrots $(Daucus \ carota)$,somatic embryogenesis is a key process.
Small pieces of carrot root (explants) are cultured in a nutrient medium to form a callus.
From this callus,somatic embryos,also known as embryoids,are developed.
These embryoids eventually grow into complete plantlets,which can then be transferred to soil.

(A) The technique of parasexual fusion,also known as somatic hybridization,involves the fusion of protoplasts from two different plant species.
This technique was first successfully demonstrated by $Harris$ and $Watkins$ in $1965$ using animal cells,but in the context of plant protoplast fusion,it is a landmark technique in plant biotechnology.
Therefore,the correct answer is $Harris$ and $Watkins$.

(D) Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism.
To produce haploid plants via tissue culture,the explant must contain haploid cells.
Root tips,stem apices,and leaves are composed of diploid $(2n)$ somatic cells.
Anthers contain pollen grains (microspores),which are haploid $(n)$ structures.
Therefore,culturing anthers or microspores is the standard method to produce haploid embryos and subsequently haploid plants.

(C) Tissue culture,specifically micropropagation,allows for the rapid multiplication of plants from a small amount of parental tissue.
Because the plants are produced through asexual reproduction (mitosis),the offspring are genetically identical to the parent plant.
This is of great economic importance because it allows for the mass production of genetically uniform populations of elite (high-yielding or disease-resistant) plant species in a short period.

(C) somatic hybrid is a plant produced by the fusion of protoplasts from two different plant species or varieties. This process involves the removal of cell walls followed by the fusion of the cytoplasm and nuclei of the two cells,which is a technique used in plant tissue culture to create new genetic combinations that cannot be achieved through sexual reproduction.

(D) Somaclonal variation refers to the genetic variations observed in plants that are regenerated from tissue culture.
These variations arise due to the stress of the culture environment,the use of growth regulators,or the duration of the culture period.
Since plants raised through tissue culture are clones of the parent,any deviation from the parent's genotype is termed as somaclonal variation.
Therefore,the correct answer is $D$.

(A) The first successful production of haploid plants through pollen culture was achieved in $Datura$ $innoxia$ by Guha and Maheshwari in $1964$.
This technique is significant in plant breeding for the rapid development of homozygous lines.

(C) The tissue culture technique is based on the totipotent nature of plant cells.
$G. Haberlandt$ $(1902)$ is considered the father of plant tissue culture because he first proposed the concept of cellular totipotency and attempted to culture plant cells in vitro.
Therefore,the correct option is $C$.

(B) The ability of a single plant cell to divide and differentiate into a complete, mature plant is known as $Totipotency$.
This biological phenomenon forms the fundamental basis for $Tissue \text{ } culture$ techniques, where explants are grown in a nutrient medium to regenerate whole plants.

(C) The cells of root tips and young leaves are diploid $(2n)$.
The endosperm is triploid $(3n)$ in angiosperms.
Pollen grains are haploid $(n)$ as they are the male gametophytes produced after meiosis.
Therefore,culturing pollen grains (anther culture) is the standard technique used to produce haploid plants.

(C) Somatic hybridization is a technique where protoplasts from two different plant species are fused to create a hybrid cell.
To facilitate the fusion of these protoplasts,a chemical agent is required.
Polyethylene glycol $(PEG)$ is the most commonly used chemical fusogen in this process because it effectively induces the fusion of protoplast membranes.
Therefore,the correct material used is Polyethylene glycol.

(B) In plant tissue culture,any part of a plant taken out and grown in a test tube under sterile conditions in special nutrient media is called an $Explant$.
$1$. $Inoculant$ refers to the material used for inoculation.
$2$. $Clone$ refers to a group of genetically identical individuals.
$3$. $Somaclone$ refers to plants that are genetically identical to the original plant from which they were grown via tissue culture.
Therefore,the correct term for the tissue used to initiate the culture is $Explant$.

(D) An explant is any part of a plant taken out and grown in a test tube under sterile conditions in special nutrient media.
$(a)$ Protoplast culture involves the use of isolated protoplasts (cells without cell walls) as explants,which is a significant technique in plant biotechnology.
$(b)$ Embryo culture involves excising a young embryo from a seed and growing it in a culture medium,which is useful for producing rare hybrids that might otherwise fail to germinate.
$(c)$ Pollen culture is a widely used method for the production of haploid plants.
Since all these parts can be used as explants for tissue culture,the correct answer is $(d)$.

(D) Tissue culture requires a specialized laboratory environment to ensure successful growth and prevent contamination.
Complete sterilization of all glassware (flasks,petri dishes,test tubes) and instruments is essential to eliminate microbes and other living organisms that could interfere with the culture.
The nutrient medium used for the growth of explants is adjusted to a specific $pH$ range,typically between $5.0$ and $6.0$,to support optimal cellular activity.
Furthermore,the cultures are maintained under strictly controlled environmental conditions,including light and a temperature range of $18^{\circ}C$ to $25^{\circ}C$.

(B) Tissue culture is a technique of growing plant cells,tissues,or organs in a sterile,nutrient-rich culture medium under controlled environmental conditions. This method allows for the regeneration of whole plants from a single cell or a small group of cells (explants),bypassing the need for seeds. This process is widely used for micropropagation and the production of disease-free plants.

(C) The most preferred organ for tissue culture is the shoot tip.
The major advantage of using shoot tip culture for the exchange of germplasm is that these tissues are generally virus-free.
Even if the parent plant is infected with a virus,the apical meristem (shoot tip) remains free from the virus because the virus cannot keep pace with the rapid rate of cell division in the meristematic region.
Therefore,it is the most reliable method for producing disease-free plants.

(D) . Coconut milk is rich in cytokinins and is used as a natural liquid nutritive medium for tissue culture.

(B) Somaclonal variations are genetic variations observed in plants regenerated from tissue culture. These variations occur during the process of callus differentiation when cells undergo rapid division and reorganization in an artificial culture medium.

(B) When two plants grow in different seasons or different geographical regions,their flowering times may not coincide,making natural cross-pollination impossible.
In such cases,the technique of $In$ $vitro$ fertilization or $Tissue$ $culture$ (specifically embryo rescue or protoplast fusion) is used to overcome these barriers.
$Tissue$ $culture$ allows for the manipulation of plant cells and tissues under controlled laboratory conditions,enabling the production of hybrids from plants that would otherwise be unable to cross-breed.

(A) The technique of producing thousands of plants through tissue culture is called $Micropropagation$.
Each of these plants will be genetically identical to the original plant from which they were grown,i.e.,they are $somaclones$.
Many important food plants like tomato,banana,apple,etc.,have been produced on a commercial scale using this method.

(B) Somatic hybridisation,also known as parasexual hybridisation,is a technique that involves the fusion of isolated protoplasts from two different plant species to produce a hybrid cell.
This process allows for the combination of desirable traits from different species that cannot be crossed through conventional sexual reproduction.

(A) In plant tissue culture,when an explant is grown in a suitable culture medium,the cells undergo division to form an unorganized,undifferentiated mass of cells. This mass is known as $Callus$.

(A) In superovulation and embryo transplantation, embryos can be preserved for a long duration at very low temperatures using liquid nitrogen.
The standard temperature for cryopreservation of embryos is $-196^{\circ}C$.

(B) Tissue culture is a modern technique used in plant biotechnology for the rapid multiplication of plants.
It involves the growth of tissues or cells in an artificial medium under sterile conditions.
Unlike traditional methods like sericulture,apiculture,and pisciculture,which have been practiced for centuries,tissue culture relies on advanced laboratory techniques and cellular biology principles.

(C) Parasexual hybridization refers to the fusion of somatic protoplasts from different sources to create a hybrid cell. This process occurs without the involvement of sexual reproductive structures or gametes. It is commonly observed in fungi,where it allows for genetic recombination through the fusion of somatic cells rather than sexual fusion.

(A) The correct answer is $A$.
Tissue culture is a modern technique used in agricultural biotechnology for the rapid propagation and improvement of crops.
It involves the growth of plant cells,tissues,or organs in a sterile nutrient medium.
Besides crop improvement,it is also widely used in the production of secondary metabolites such as antibiotics,alkaloids,and dyes.

(A) Tissue culture is a technique of growing plant cells,tissues,or organs in a sterile nutrient medium.
It allows for the production of new plants from a small piece of plant tissue (explant) without the need for seeds.
This process is widely used for micropropagation and cloning of plants.

(C) Tissue culture is a technique of growing plant cells, tissues, or organs in a sterile environment on a nutrient culture medium of known composition.
It involves the maintenance of fragments of cells or tissues alive after their removal from an organism, allowing them to grow and differentiate into new plants under controlled laboratory conditions.
Therefore, option $C$ is the most accurate definition among the choices provided.

(B) The concept of tissue culture was pioneered by Gottlieb Haberlandt in $1902$. However,in the context of animal tissue culture,Alexis Carrel is widely recognized for his significant contributions and for launching the technique of culturing animal cells in vitro during the early $20$th century. Among the given options,Carrel is the correct choice.

(B) Coconut milk is a rich source of $Cytokinin$ (specifically $Zeatin$).
In plant tissue culture,$Cytokinin$ is essential for promoting cell division and shoot differentiation.
Therefore,it is added to the culture medium to support the growth and development of explants.

(D) Somatic hybridization is a technique where protoplasts from two different plant species are fused to create a hybrid cell. This method allows for the transfer of genetic material,such as the streptomycin resistance gene,between species like $Nicotiana$ $tabacum$ and $Nicotiana$ $sylvestris$ that might not be able to cross-breed through conventional sexual hybridization. Therefore,the correct method is somatic hybridization.

(B) Somaclones are genetically identical plants produced from a single parent through asexual reproduction or vegetative propagation.
In plant biotechnology, these are typically obtained through $Tissue \text{ } culture$ (specifically micropropagation).
Since the plants are regenerated from somatic cells (explants) without meiosis, they maintain the same genetic makeup as the parent plant.
Therefore, the correct option is $B$.

(B) Somatic hybridization is a technique where protoplasts from two different plant species are fused to create a hybrid plant.
$1$. $Bt$ cotton is a transgenic plant created using recombinant $DNA$ technology.
$2$. Pomato is a somatic hybrid produced by the fusion of protoplasts of potato ($Solanum$ $tuberosum$) and tomato ($Lycopersicon$ $esculentum$).
$3$. Golden rice is a genetically modified crop engineered to produce beta-carotene.
Therefore,the correct example of somatic hybridization is Pomato.

(C) The method used to obtain virus-free plants is $Meristem$ $culture$.
Even if a plant is infected with a virus, the $meristem$ (apical and axillary) remains free of the virus because the virus cannot replicate in the rapidly dividing cells of the $meristem$ due to the high metabolic activity and the presence of specific antiviral proteins.
By isolating the $meristem$ and growing it in vitro, we can obtain healthy, virus-free plants.

(A) The ability of a single plant cell to divide and differentiate into a complete plant is known as $Cellular \text{ } totipotency$. In tissue culture, pollen grains (which are haploid) can be induced to form embryos (haploid embryos) when placed in a suitable nutrient medium. This phenomenon is a direct application of the property of $totipotency$, where the cell retains the genetic potential to develop into an entire organism under specific laboratory conditions.

(D) Somaclonal variation refers to the genetic variations observed in plants regenerated from tissue culture (callus culture).
These variations arise due to the instability of the genome during the process of in vitro culture.
Since tissue culture involves the asexual propagation of cells,the resulting plants are expected to be genetically identical to the parent (clones); however,mutations or epigenetic changes during the culture process lead to 'somaclonal variations'.
Therefore,the correct option is $D$.

(B) Cellular totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism.
In plants,this property is widely observed,where a single somatic cell can regenerate an entire plant.
This is the fundamental principle behind plant tissue culture,which allows for the cloning of plants from explants.
While some animal cells show pluripotency,true totipotency is a characteristic feature primarily associated with plant cells in the context of biological studies.