Tissue Culture Questions in English

(A) In plant tissue culture,suspension culture involves the growth of cells or small aggregates of cells in a liquid medium. To induce cell division and proliferation in the callus,the liquid medium is supplemented with specific plant growth regulators. Auxins,such as $2, 4-D$ ($2$,$4$-Dichlorophenoxyacetic acid),are commonly used to promote cell division and callus growth in suspension cultures.

(A) Suspension culture involves the growth of cells in a liquid medium where they are kept in motion. In this process,the cells proliferate to form a mass of undifferentiated cells known as callus or cell aggregates. These cells are typically undifferentiated,meaning they have not yet specialized into specific tissue types like xylem or phloem. Therefore,the correct answer is $A$.

(A) Suspension culture is a technique in plant tissue culture where single cells or small groups of cells are dispersed and grown in a liquid nutrient medium.
This method allows for the rapid multiplication of cells and is widely used for the production of secondary metabolites and for genetic transformation studies.

(A) In plant tissue culture,maintaining an aseptic environment is crucial. Instruments like forceps,scalpels,and needles are sterilized using $UV$ light (ultraviolet radiation) in a laminar air flow cabinet to ensure they are free from microbial contamination. $UV$ light has germicidal properties that effectively destroy the $DNA$ of microorganisms,preventing their growth.

(C) Interspecific hybridization often leads to the failure of endosperm development, causing the hybrid embryo to abort before maturity. To overcome this, the technique of $Embryo \text{ } rescue$ (or embryo culture) is used. In this method, the immature hybrid embryo is aseptically removed from the seed and cultured on a suitable nutrient medium to allow it to develop into a viable plantlet. Therefore, the correct method to obtain hybrid embryos from such crosses is embryo rescue.

(C) The technique of isolating a small embryo from a seed and growing it on a nutrient culture medium under sterile conditions is known as $Embryo$ $culture$.
This technique is widely used in plant tissue culture to overcome seed dormancy,rescue embryos from incompatible crosses,or to propagate plants that produce seeds with poor germination rates.

(D) The process of tissue culture begins with the selection of an explant (a small piece of plant tissue).
Once placed on a suitable nutrient medium,the cells of the explant undergo rapid cell division.
This mass of undifferentiated,proliferating cells is known as callus.
To induce further growth or organogenesis,specific plant growth regulators like cytokinin are added to the medium.
Finally,these cells differentiate into meristematic or specialized tissues to form new plantlets.
Therefore,the correct sequence is: Explant $\rightarrow$ Cell division $\rightarrow$ Callus $\rightarrow$ Addition of cytokinin $\rightarrow$ Cells differentiate into meristematic tissue.

(A) In plant tissue culture,$Agar-agar$ is widely used as a solidifying agent to prepare the culture medium for callus growth. It provides a stable,semi-solid support that allows the callus to grow while remaining in contact with the essential nutrients,vitamins,and hormones provided in the medium. $Agar-agar$ is derived from red algae and is preferred because it is not digested by plant enzymes and does not interfere with the growth of the tissue.

(B) Plants developed through plant tissue culture are genetically identical to the original plant from which they were derived. These are known as $Somaclones$ because they are produced from somatic cells through asexual reproduction (micropropagation). Since they are clones,they possess the same genetic makeup as the parent plant.

(C) Callus culture is a method in plant tissue culture where an unorganized mass of cells,known as callus,is formed.
Over time,these cells undergo differentiation to form small,specialized cell groups or organs (like shoots or roots) through the process of organogenesis or somatic embryogenesis.
Therefore,callus culture is the primary method where undifferentiated cell clusters differentiate into specialized structures.

(B) Embryo rescue is a technique used in $Plant \text{ } tissue \text{ } culture$ to assist the development of embryos that might otherwise fail to survive.
It is particularly useful in $Interspecific \text{ } hybridization$ (crossing between two different species) where the embryo often aborts due to endosperm incompatibility or other developmental barriers.
While it is used to facilitate interspecific hybridization, the technique itself is a fundamental component of $Plant \text{ } tissue \text{ } culture$ technology.

(B) In plant tissue culture,when plant cells are grown on a nutrient medium,they undergo rapid division to form an unorganized,undifferentiated mass of cells. This mass is known as $Callus$.

(D) Plant tissue culture is a collection of techniques used to maintain or grow plant cells,tissues,or organs under sterile conditions on a nutrient culture medium of known composition.
Common methods of plant tissue culture include:
$1$. Callus culture: Culturing unorganized mass of cells (callus) on a solid medium.
$2$. Suspension culture: Culturing cells or small aggregates of cells in a liquid medium.
$3$. Embryo culture: Culturing isolated embryos to produce whole plants.
Since all these are established techniques in plant biotechnology,the correct answer is $D$.

(D) Plant tissue culture is a technique of maintaining and growing plant cells,tissues,or organs in a sterile environment on a nutrient culture medium of known composition.
It relies on the principle of totipotency,which is the ability of a plant cell to regenerate into a complete plant.
Therefore,option $D$ is the most comprehensive and accurate definition as it includes cells,tissues,and organs,as well as the aspects of maintenance and growth.

(D) In plant tissue culture,the part of the plant that is excised and used to initiate a culture is known as the $Explant$.
This can be any part of the plant such as a piece of leaf,stem,root,or even a single cell.
Once placed on a suitable nutrient medium under sterile conditions,the $Explant$ begins to divide and grow to form a mass of undifferentiated cells called $Callus$.

(A) In the process of tissue culture,maintaining an aseptic environment is crucial to prevent contamination by microorganisms.
Instruments used in tissue culture,such as forceps,scalpels,and needles,are typically sterilized using an autoclave (high pressure and temperature) or by flaming.
However,in the context of laminar airflow cabinets used for tissue culture,$UV$ (Ultraviolet) light is commonly employed to sterilize the working surface and the air within the cabinet before starting the procedure.
Therefore,among the given options,$UV$ light is the correct method used for sterilization in this context.

(C) In plant tissue culture,specifically during callus induction and organogenesis,the balance between $Auxin$ and $Cytokinin$ is crucial.
$Auxin$ promotes root development,while $Cytokinin$ promotes shoot development.
By manipulating the ratio of these two hormones in the culture medium,researchers can control the differentiation of the callus into roots,shoots,or embryos.
Therefore,the correct combination used in the medium is $Cytokinin$ and $Auxin$.

(B) In plant tissue culture,the explant is placed on a nutrient medium to induce cell division. The formation of callus,which is an unorganized mass of cells,typically occurs after $2$ to $3$ weeks of incubation under controlled conditions.

(A) Suspension culture is a technique in which single cells or small groups of cells are suspended in a liquid medium and agitated to maintain them in a dispersed state.
This method allows for the rapid growth of cells and is widely used in plant tissue culture for the production of secondary metabolites and biomass.
In contrast,callus culture involves growing cells on a solid medium,and embryo culture involves the isolation and growth of embryos.

(B) In plant tissue culture,specifically in suspension culture,$2,4-D$ (a synthetic $Auxin$) is commonly added to the medium.
$Auxins$ are essential for inducing cell division and promoting the growth of callus or cell suspensions.
While $Cytokinins$ are also used,$Auxins$ are the primary growth regulators required to initiate and maintain the growth of suspension cultures.

(B) Suspension culture involves the growth of cells or small aggregates of cells in a liquid medium that is constantly agitated.
Due to the continuous movement and better availability of nutrients and oxygen to each cell,the growth rate in suspension culture is significantly faster than that of callus culture,which is grown on a solid medium where nutrient diffusion is slower.

(A) In plant tissue culture, $Suspension \text{ culture}$ involves the growth of single cells or small groups of cells in a liquid medium. A $rotary \text{ shaker}$ is essential in this method to provide continuous agitation, which ensures proper aeration, nutrient distribution, and prevents the cells from clumping together.

(C) In suspension culture, cells or cell aggregates are grown in a liquid medium.
To ensure proper aeration and to prevent the cells from settling at the bottom, the culture flask is placed on a rotary shaker.
The rotary shaker is typically operated at a speed of $100$ to $250\, rpm$ (revolutions per minute).
This constant agitation helps in maintaining a uniform distribution of nutrients and oxygen throughout the medium.

(C) In $Callus$ $culture$, the explant (a piece of plant tissue) is placed on a nutrient medium. The cells divide to form an unorganized mass of cells known as $Callus$. Under specific hormonal conditions, these cell aggregates in the $Callus$ differentiate to form small, specialized cell groups or organs (like shoots or roots), a process known as organogenesis.

(A) The process of transferring a portion of an existing culture into a fresh medium or new glass apparatus to allow for continued growth and multiplication of cells or microorganisms is known as $Subculturing$. This is a standard procedure in microbiology and plant tissue culture to maintain cell lines.

(C) Callus and suspension cultures are primarily used for the production of secondary metabolites,isolation of protoplasts,production of cell biomass,and rapid clonal propagation (micropropagation).
Regeneration of plumules is a specific developmental process that typically occurs during somatic embryogenesis or organogenesis from organized tissues,but it is not considered a primary application or objective of undifferentiated callus or suspension culture systems,which are designed to maintain cells in an unorganized state.

(C) The process of plant tissue culture involves several steps.
$A$. Placing the selected explant in a suitable culture medium is the initial step of inoculation.
$B$. In suspension culture,growth regulators like $2,4-D$ (a synthetic auxin) are often added to promote cell division and growth.
$C$. In callus culture,a balance of auxins and cytokinins is typically used to induce callus formation,not necessarily gibberellins and auxins.
$D$. The process of transferring a portion of the culture to a fresh medium in new glassware is correctly defined as subculturing.
Therefore,statement $C$ is considered false in the context of standard tissue culture protocols where cytokinins are the primary requirement alongside auxins for callus induction.

(B) The process of isolating an embryo from a seed and growing it on a nutrient medium under aseptic conditions is called $Embryo \ culture$. This technique is often used to overcome seed dormancy,to rescue embryos from incompatible crosses,or to propagate rare plants.

(B) Embryo culture is a technique used to overcome seed dormancy and to rescue embryos from seeds that fail to germinate due to various reasons,such as long-term dormancy or incompatibility. By isolating the embryo and providing it with appropriate nutrient media under controlled conditions,the development of the plumule and radicle can be induced,leading to the formation of a complete plantlet.

(D) Embryo culture is a technique in plant tissue culture where an embryo is isolated from the seed and grown in a nutrient medium.
$1$. It is used for rapid clonal propagation to produce a large number of genetically identical plants.
$2$. It serves as a vital tool in genetic engineering for the production of genetically modified $(GM)$ plants.
$3$. It is used to overcome seed dormancy and incompatibility barriers,thereby aiding in the development of new and useful plant varieties.
Therefore,all the mentioned purposes are valid applications of embryo culture.

(D) Embryo culture is a type of tissue culture technique used to rescue embryos that might otherwise fail to develop in vivo.
Its primary objectives include overcoming seed dormancy,rescuing hybrid embryos,and producing haploid plants.
$A$,$B$,and $C$ are standard applications of plant tissue culture techniques.
$D$ (Production of useful species) is a broad goal of plant breeding and biotechnology in general,but it is not a specific technical objective of the embryo culture process itself,as embryo culture is a tool to assist in the development of specific embryos,not a method to create new species from scratch.

(B) The correct matching is as follows:
$1$. $(a)$ $UV$ light is used for sterilization of the laminar airflow cabinet to maintain a sterile environment: $(a-r)$.
$2$. $(b)$ Protoplast isolation involves the use of enzymes like cellulase and pectinase, which is a key step in callus culture or somatic hybridization: $(b-s)$.
$3$. $(c)$ Orchid seeds are very small and lack endosperm, so they require embryo culture for germination: $(c-p)$.
$4$. $(d)$ Explant is any part of a plant taken out and grown in a test tube under sterile conditions in special nutrient media: $(d-q)$.
Therefore, the correct sequence is $(a-r), (b-s), (c-p), (d-q)$.

(A) The term $Callus$ refers to an unorganized or undifferentiated mass of cells that develops from explants (plant tissue) when grown on a nutrient medium under sterile conditions.
To induce the formation of callus and support its growth,the culture medium is supplemented with specific plant growth regulators,primarily $Auxin$ and $Cytokinin$.
Since the addition of these hormones is the specific reason why the undifferentiated mass (callus) is formed and maintained in tissue culture,$R$ provides the correct explanation for $S$.

(B) Embryo culture is a technique used to rescue embryos from seeds that exhibit prolonged dormancy or fail to germinate under natural conditions. By isolating the embryo and placing it on a nutrient-rich culture medium under controlled conditions,the dormancy can be broken,and the embryo can be induced to develop into a seedling. This is particularly useful in plant breeding and conservation of rare species.

(B) Plant tissue culture is a technique of growing plant cells,tissues,or organs in a sterile,controlled environment.
$1$. Sterilization is typically achieved using an autoclave (high pressure and steam) or chemical disinfectants,not infrared light.
$2$. The temperature for incubation is generally maintained between $20^{\circ}C$ to $28^{\circ}C$,making $24^{\circ}C$ a suitable and consistent condition for the growth of the explant.
$3$. Explants are usually placed on a solid or semi-solid nutrient medium (agar-based) rather than just a liquid medium to provide structural support.
$4$. While a quiet environment is good,it is not a technical requirement for the success of the culture process.
Therefore,maintaining the explant at $24^{\circ}C$ is a standard practice in tissue culture.

(A) Callus is an unorganized mass of actively dividing cells maintained in culture.
To maintain the callus in a laboratory setting, a solidifying agent is required to provide structural support to the medium.
Agar-agar, derived from seaweeds, is the most commonly used gelling agent in plant tissue culture media because it is inert, stable, and provides a firm surface for the callus to grow on.
Therefore, agar-agar gel is the correct medium component for callus maintenance.

(A) In plant tissue culture,callus is an undifferentiated mass of cells. To induce shoot and root development from the callus,specific plant growth regulators are added to the culture medium. Cytokinins are primarily responsible for promoting cell division and shoot differentiation in callus cultures. Therefore,cytokinin is the essential growth promoter added to the medium.

(A) In suspension culture,the culture medium is continuously agitated using a rotary shaker. This process is essential for two main reasons:
$1$. It ensures proper aeration,which facilitates the exchange of gases like $O_2$ and $CO_2$ between the culture medium and the atmosphere.
$2$. It ensures uniform distribution of nutrients and cells throughout the medium,preventing the cells from settling at the bottom.
Therefore,the primary purpose is to facilitate gas exchange and maintain a homogeneous environment.

(D) Plant tissue culture is a technique of growing plant cells,tissues,or organs in a sterile,nutrient-rich culture medium under controlled environmental conditions.
In this process,the explant (the part of the plant used for culture) undergoes cell division and differentiation.
As the cells divide and grow,they form a mass of undifferentiated cells called callus.
Consequently,the primary objective and essential event in this technique is the proliferation of cells,which leads to an increase in the biomass of the cells or tissues.

(C) Embryo rescue is a technique used in plant tissue culture to assist the development of embryos that might otherwise fail to mature.
It is particularly useful for obtaining viable plants from interspecific or intergeneric crosses where the embryo often aborts due to endosperm failure.
The primary application of this technique is the regeneration of plantlets from these immature or hybrid embryos,which would not survive under natural conditions.

(D) In plant tissue culture,a callus is defined as an unorganized mass of undifferentiated cells that proliferate from an explant (a piece of plant tissue) when cultured on a nutrient medium.
These cells are actively dividing but have not yet specialized into specific plant tissues or organs.
Under appropriate hormonal conditions,the callus can be induced to differentiate into shoots,roots,or somatic embryos.

(A) In plant tissue culture,callus is an undifferentiated mass of cells grown on a nutrient medium.
To induce growth and differentiation,specific plant growth regulators are added to the medium.
Auxins and cytokinins are the most important plant hormones used in tissue culture.
Auxins promote cell elongation and root initiation,while cytokinins promote cell division (cytokinesis) and shoot initiation.
Therefore,both statements are scientifically accurate as they act as growth promoters and initiate cell division in the culture.

(B) Statement $(i)$ is correct: Callus formation typically occurs within $2$ to $3$ weeks of culture initiation.
Statement $(ii)$ is incorrect: Suspension culture generally shows faster growth compared to callus culture because cells are in direct contact with the nutrient medium.
Statement $(iii)$ is correct: Orchid seeds are minute and lack endosperm or stored food,requiring symbiotic fungi for germination.
Statement $(iv)$ is incorrect: $2,4-D$ (a synthetic auxin) is widely used in both callus culture and suspension culture to promote cell division and growth.
Therefore,statements $(ii)$ and $(iv)$ are incorrect.

(C) The correct matching is as follows:
$(i)$ Callus culture: It is an unorganized,undifferentiated mass of cells derived from explants. Thus,$(i-C)$.
$(ii)$ Suspension culture: It involves the growth of cells in a liquid medium,often resulting in a differentiated mass or specific cell types. Thus,$(ii-B)$.
$(iii)$ Embryo culture: It is primarily used for the rescue of hybrid embryos that might otherwise fail to develop in vivo. Thus,$(iii-A)$.
Therefore,the correct sequence is $(i-C, ii-B, iii-A)$.

(A) In plant tissue culture,the differentiation of callus into organs (organogenesis) is controlled by the ratio of plant growth regulators in the medium.
Specifically,a high concentration of $Auxin$ relative to $Cytokinin$ promotes the development of roots (rhizogenesis).
Conversely,a high concentration of $Cytokinin$ relative to $Auxin$ promotes the development of shoots (caulogenesis).
Therefore,$Auxin$ is the hormone responsible for inducing root formation in callus culture.

(D) In plant tissue culture,auxins are essential for inducing cell division and root formation.
$NAA$ (Naphthalene acetic acid),$IBA$ (Indole$-3-$butyric acid),and $2,4-D$ ($2$,$4$-Dichlorophenoxyacetic acid) are all synthetic auxins widely used in laboratory settings.
These auxins are commonly employed in both callus induction and suspension culture media to promote growth and morphogenesis.
Therefore,all the listed auxins are standard choices for these culture techniques.

(D) Callus and suspension cultures are fundamental techniques in plant tissue culture.
$1$. Regeneration of shoots: Callus can be induced to differentiate into shoots (organogenesis) under specific hormonal conditions.
$2$. Production of cell biomass: Suspension cultures allow for the rapid growth of cells in liquid media,which is used for the large-scale production of secondary metabolites or biomass.
$3$. Isolation of protoplasts: Callus and suspension cultures serve as excellent sources for isolating protoplasts,which are plant cells without cell walls,used in genetic engineering and somatic hybridization.
Therefore,all the given options are correct applications.

(C) The correct matching is as follows:
$(1)$ Callus culture: Callus is an unorganized,undifferentiated mass of cells derived from plant tissue culture. Thus,$(1)-(R)$.
$(2)$ Suspension culture: This involves the growth of cells or small aggregates of cells in a liquid medium,often resulting in a differentiated mass or specific cell types. Thus,$(2)-(Q)$.
$(3)$ Embryo culture: This technique is used to rescue embryos that might otherwise fail to develop,often used in hybrid embryo rescue. Thus,$(3)-(P)$.
Therefore,the correct sequence is $(1)-(R), (2)-(Q), (3)-(P)$.

(A) $A:$ Suspension culture involves the growth of single cells or small cell aggregates in a liquid medium,which allows for faster nutrient uptake and rapid growth compared to the solid callus culture.
$R:$ The use of a rotary shaker provides constant agitation,which ensures uniform distribution of nutrients and improves oxygen availability (aeration) for the cells,thereby supporting faster growth.
Since the rapid growth in suspension culture is directly facilitated by the improved nutrient mixing and aeration provided by the rotary shaker,$R$ is the correct explanation of $A$.

(A) In plant tissue culture,explants are grown on a nutrient medium containing essential minerals,vitamins,and carbon sources.
As the cells or tissues grow and divide,they consume these nutrients from the medium to support their metabolic activities and increase their biomass.
Therefore,the depletion of nutrients in the medium $(A)$ is a direct consequence of the rapid growth and increase in biomass of the cultured cells or tissues $(R)$.
Thus,$R$ is the correct explanation for $A$.