Tissue Culture Questions in English

(C) Banana plants are typically propagated vegetatively using suckers (specifically sword suckers). In commercial tissue culture,the method used for rapid multiplication is micropropagation (a form of tissue culture). However,among the traditional vegetative methods provided in the options,rhizome cuttings are the most effective way to propagate banana plants as they contain the meristematic tissue necessary for growth.

(A) An embryoid is a structure that resembles an embryo but is derived from somatic cells rather than from the fusion of gametes. These are also known as somatic embryos. They are commonly produced through tissue culture techniques,where somatic cells are induced to develop into embryo-like structures that can eventually grow into complete plants.

(C) Shoot tip culture is a vital technique in plant tissue culture. Shoot tips (meristems) are generally virus-free because viruses cannot spread rapidly through the actively dividing meristematic tissues of the plant. By using this method,virus-free clonal plants can be produced,which is essential for the safe international exchange of germplasm. Therefore,option $C$ is the correct answer.

(A) Hardening is a critical step in plant tissue culture where in vitro grown plantlets are gradually acclimatized to the external environment.
During this process,plantlets are initially kept in conditions of low light intensity and high humidity for a short period to prevent desiccation and shock.
This helps the plantlets adapt to the greenhouse or field conditions before they are fully transplanted.

(D) Tissue culture is a technique used to grow plant cells,tissues,or organs in a sterile environment on a nutrient culture medium.
$1$. Micropropagation: It allows for the rapid production of thousands of plants in a short time using explants.
$2$. Production of disease-free plants: By using meristem culture,it is possible to recover healthy plants from diseased ones because the meristem is generally free of viruses.
$3$. Androgenic haploid plants: It is used to produce haploid plants through pollen grain culture,which is useful for creating homozygous lines in plant breeding.
Therefore,all the given options are correct applications of tissue culture.

(C) Pollen culture is a technique used in plant tissue culture to produce haploid plants.
By culturing pollen grains (microspores) on a suitable nutrient medium,they undergo embryogenesis to form haploid plants.
These haploid plants are highly useful in plant breeding programs for the rapid development of homozygous lines,which helps in the production of superior hybrid varieties.

(D) Agar is a polysaccharide obtained from marine algae (specifically red algae like Gelidium and Gracilaria).
It is widely used in biotechnology as a solidifying agent in culture media for tissue culture and as a matrix for gel electrophoresis to separate $DNA$ fragments based on their size.

(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 exhibited by all living plant cells that possess an intact nucleus and the potential to dedifferentiate. This principle forms the basis of plant tissue culture,where a single explant can be used to regenerate an entire plant.

(A) Haploid plants are plants that contain only one set of chromosomes $(n)$.
In plant tissue culture,haploid plants can be produced by culturing gametophytic tissues.
Anther culture is the most common and effective method for producing haploid plants because the pollen grains (microspores) within the anther are haploid.
When these microspores are cultured on a suitable nutrient medium,they undergo embryogenesis or callus formation to develop into haploid plants.

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

(A) Hardening is a critical step in micropropagation where tissue-cultured plantlets are gradually acclimatized to the external environment.
Initially,these plantlets are grown in a controlled,high-humidity,and low-light environment within the laboratory.
During hardening,they are slowly exposed to lower humidity and higher light intensity to prepare them for survival in the field or greenhouse conditions.
This process prevents transplant shock and ensures the survival of the plantlets.

(D) Somatic hybridization is a technique in plant tissue culture where protoplasts from two different plant species are fused to form a somatic hybrid.
$1$. The primary goal is to combine desirable traits from two different species that cannot be crossed sexually.
$2$. This process often results in the production of useful allopolyploids,which possess the combined genetic material of both parents.
$3$. Therefore,somatic hybridization leads to the formation of somatic hybrids and the creation of allopolyploids with new,beneficial characteristics.
$4$. Thus,both $(B)$ and $(C)$ are correct outcomes of this process.

(D) Tissue culture is a technique used to grow plant cells,tissues,or organs in a sterile environment on a nutrient culture medium of known composition.
$1$. Micropropagation: It allows for the rapid multiplication of plants,producing thousands of plants in a short time.
$2$. Production of disease-free plants: By using meristem culture,it is possible to obtain virus-free plants even from infected parent plants.
$3$. Production of androgenic haploid plants: Through anther or pollen culture,haploid plants can be produced,which are useful for genetic research and breeding programs.
Therefore,all the given options are correct applications of tissue culture.

(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 into a complete plant.
This is the fundamental principle behind plant tissue culture,which allows for the propagation of plants from explants.
Therefore,it is a characteristic feature of plant cells.

(D) The $meristem$ (apical and axillary) is free from viruses even in an infected plant. This is because the virus fails to multiply in the rapidly dividing cells of the $meristem$ due to the high metabolic activity and the presence of antiviral substances. Therefore,by culturing the $meristem$ of an infected plant,we can obtain virus-free plants. This technique is widely used in horticulture and agriculture for the production of disease-free clones.

(B) In plant tissue culture,callus formation is induced by the balance of auxins and cytokinins. $BAP$ (Benzyl amino purine) is a synthetic cytokinin that is widely used in tissue culture media to promote shoot development and callus induction from explants like shoot tips.

(C) In interspecific hybridization, the hybrid embryo often fails to develop normally due to the degeneration of the endosperm, which provides essential nutrients for the developing embryo. To rescue such embryos, they are excised from the seed at an early stage and grown on a nutrient medium under sterile conditions. This technique is known as $Embryo culture$ or embryo rescue. Therefore, the correct option is $C$.

(C) Haploid plants were first obtained through anther culture by Guha and Maheshwari in $1964$. The plant species used for this pioneering experiment was $Nicotiana$ $tabacum$ (Tobacco). This technique is widely used in plant breeding to produce homozygous lines.

(C) Shoot tip culture is preferred for the international exchange of germplasm because the meristematic tissue in the shoot tip is generally free from viruses. Even in virus-infected plants,the apical meristem remains virus-free due to the high rate of cell division and lack of vascular connection with the infected tissues. By culturing these shoot tips,researchers can produce virus-free clonal plants,which is essential for safe international germplasm exchange. Therefore,option $C$ is the correct answer.

(C) The rapid multiplication of banana plants is achieved through $Micropropagation$ (a type of $Tissue \text{ } culture$).
In this technique, small pieces of plant tissue are grown in a sterile nutrient medium to produce a large number of genetically identical plantlets in a short period.
This is highly effective for commercial propagation of disease-free banana plants.

(C) Protoplast fusion is a technique in plant biotechnology where two different protoplasts are fused to create a hybrid cell. This process was first demonstrated by $E.C. Cocking$ in $1960$ using enzymes to remove the cell wall of plant cells.

(C) 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 $Explant$.
$Scion$ and $Stock$ are terms used in grafting.
$Callus$ is an unorganized mass of cells produced from the explant during the culture process.

(B) The process of transferring cells from an old culture medium to a fresh medium to allow for continued growth and proliferation is known as $Subculturing$ (or $Passaging$). This is essential in cell culture to prevent the cells from becoming over-confluent,which can lead to nutrient depletion and the accumulation of toxic metabolic waste products.

(D) $Somaclonal$ variation refers to the genetic variations observed in plants regenerated from tissue culture.
Since the plants are derived from a single parent cell or tissue (clones), they are expected to be genetically identical.
However, during the process of $in$ $vitro$ culture, spontaneous mutations or chromosomal changes can occur, leading to phenotypic and genotypic differences among the regenerated plants.
These variations are known as $Somaclonal$ variations.

(A) The ability of a single cell to divide and produce all the differentiated cells in an organism is called $Totipotency$.
This is a characteristic feature of plant cells and zygotes.
$Pluripotency$ refers to the ability of a cell to differentiate into most,but not all,cell types.
$Multipotency$ refers to the ability of a cell to differentiate into a limited number of cell types.
$Unipotency$ refers to the ability of a cell to produce only one cell type.

(D) 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 property allows a cell to develop into a complete,mature organism.

(D) Totipotency is the genetic potential of a plant cell to develop into a complete organism.
This means that any living plant cell,whether it is from the root,stem,leaf,or any other part,possesses the inherent capacity to divide and differentiate to form a whole new plant under suitable laboratory conditions (tissue culture).
Therefore,since all the options $(A)$,$(B)$,and $(C)$ describe the generation of a complete organism from different plant parts,the correct answer is $(D)$.

(B) Embryo culture is a type of plant tissue culture technique used primarily to rescue embryos that might otherwise fail to develop in vivo (e.g., in wide hybridization or seed dormancy).
$A$. Rapid clonal propagation is a standard application of tissue culture.
$B$. Producing biomass of cells is typically associated with suspension cultures or bioreactor studies, not specifically embryo culture.
$C$. Genetically modified plants can be produced using embryo culture as a target for transformation.
$D$. Development of useful plant varieties is a broad goal of plant breeding and biotechnology, often aided by embryo culture.
Therefore, the production of biomass of cells is not a primary objective of embryo culture.

(D) In plant tissue culture,the medium is kept in containers (like flasks or test tubes) for a long duration.
Over time,water molecules from the nutrient medium escape into the headspace of the container and eventually into the surrounding environment,a process known as evaporation.
This loss of water leads to a decrease in the total volume of the culture medium,which can change the concentration of nutrients and potentially affect the growth of the plant tissues.

(C) Callus and suspension cultures are fundamental techniques in plant tissue culture.
$1$. $Isolation \, of \, protoplasts$: Callus tissue is often used as a source to isolate protoplasts for somatic hybridization.
$2$. $Regeneration \, of \, plantlets$: Through organogenesis or somatic embryogenesis, callus can regenerate into complete plantlets.
$3$. $Production \, of \, cell \, biomass$: Suspension cultures are specifically used for the large-scale production of plant cell biomass and secondary metabolites.
$4$. $Obtaining \, interspecific \, hybrid \, plantlets$: While protoplast fusion can lead to interspecific hybrids, the direct application of callus and suspension culture itself is not primarily defined as a method for obtaining interspecific hybrid plantlets; this is a result of somatic hybridization techniques. However, in the context of standard biology curriculum, the option $C$ is considered the least direct application compared to the others.

(A) Tissue culture is a technique used to grow plant cells,tissues,or organs in a sterile environment on a nutrient culture medium of known composition. The fundamental biological principle behind this is $Totipotency$,which is the ability of a single plant cell to divide and differentiate to produce an entire new plant. Therefore,through tissue culture,the property of $Totipotency$ is utilized to regenerate whole plants from explants.

(A) In tissue culture,sterilization is a critical step to prevent contamination. Equipment is typically sterilized using an autoclave (high pressure and steam) or chemical disinfectants,not infrared light. Infrared light is not an effective method for achieving the level of sterility required for tissue culture. Therefore,the statement regarding the use of infrared light is incorrect.

(A) The process of transferring a portion of an existing culture into a fresh medium or new glassware to maintain the culture is known as $Subculturing$. This is essential in microbiology and plant tissue culture to prevent the depletion of nutrients and the accumulation of toxic metabolic waste products.

(A) Plant tissue culture is a technique used to grow plant cells,tissues,or organs under sterile conditions on a nutrient culture medium.
Key processes involved include the uptake of nutrients from the medium,leading to an increase in biomass (cell proliferation).
As cells grow and divide,they consume nutrients,leading to the depletion of the medium.
Evaporation may occur,but it is an environmental factor,not a biological or essential process for the success of tissue culture.
An increase in temperature due to cell proliferation is not a standard or essential event in this process; in fact,temperature is strictly controlled by the incubator or growth chamber.

(A) In plant tissue culture,callus is an unorganized mass of cells derived from explants. When an explant is placed on a suitable nutrient medium (like $MS$ medium) supplemented with appropriate plant growth regulators (auxins and cytokinins),the cells begin to divide and proliferate. Typically,the formation of callus from the explant takes approximately $2$ to $3$ weeks under controlled laboratory conditions.

(A) In callus culture,cells grow on a solid medium,which limits the diffusion of nutrients and oxygen to the inner cells of the callus.
In suspension culture,cells are dispersed in a liquid medium.
Using a rotary shaker provides constant agitation,which ensures uniform distribution of nutrients and efficient gas exchange (oxygen and carbon dioxide) throughout the medium.
This increased availability of nutrients and oxygen leads to a significantly faster growth rate in suspension cultures compared to callus cultures.
Therefore,both the assertion and the reason are correct,and the reason correctly explains the assertion.

(D) Plant tissue culture is a technique of growing plant cells,tissues,or organs in a sterile,controlled environment using a specific nutrient culture medium. This process allows for the maintenance and development of these plant parts into whole plants or specific structures. Therefore,option $D$ is the most comprehensive and accurate definition.

(A) In plant tissue culture,explants are grown in a nutrient-rich medium (containing carbon sources,vitamins,minerals,and growth regulators).
As the cells or tissues grow and divide,they consume these nutrients from the medium to synthesize new cellular components and increase their biomass.
Therefore,the concentration of nutrients in the medium gradually decreases over time as the biomass of the cultured cells or tissues increases.
Thus,both Assertion $A$ and Reason $R$ are true,and $R$ is the correct explanation of $A$.

(D) Plant tissue culture is a versatile technique used in biotechnology for several purposes:
$1$. Rapid clonal propagation: It allows for the production of thousands of genetically identical plants (clones) from a single explant in a short period.
$2$. Development of useful varieties: It helps in the selection and multiplication of plants with desirable traits such as disease resistance or higher yield.
$3$. Development of genetically modified plants: Tissue culture is an essential step in the process of genetic engineering,where transformed cells are regenerated into whole plants.
Therefore,all the mentioned options are correct applications of plant tissue culture.

(C) Plant tissue culture is broadly classified into two main types based on the explant used and the method of culture:
$1$. Organ culture (e.g.,meristem culture,embryo culture).
$2$. Cell/Callus culture (e.g.,suspension culture,protoplast culture).
Therefore,there are two primary categories of plant tissue culture.

(D) In suspension culture,cell aggregates or single cells are grown in a liquid medium. To prevent the cells from settling at the bottom and to ensure proper aeration and nutrient distribution,the culture is continuously agitated or shaken. This process keeps the cells in a suspended state throughout the medium.

(D) Statement $(i)$ is correct: Embryo culture is effectively used to overcome seed dormancy and produce seedlings from seeds that are difficult to germinate.
Statement $(ii)$ is correct: The fundamental process of embryo culture involves the excision of the embryo from the seed and its subsequent growth on a sterile nutrient culture medium.
Statement $(iii)$ is incorrect: Bean seeds are dicotyledonous seeds that store food in their cotyledons.
Statement $(iv)$ is incorrect: Rapid clonal propagation is primarily an application of micropropagation (tissue culture),not specifically suspension culture.
Therefore,statements $(i)$ and $(ii)$ are correct.

(D) Callus and suspension cultures are fundamental techniques in plant tissue culture.
$1$. They are used to produce genetically modified plants through transformation techniques like Agrobacterium-mediated gene transfer.
$2$. They are used to produce large quantities of biomass of cells for the extraction of secondary metabolites.
$3$. They are used for organogenesis or somatic embryogenesis to regenerate plantlets from undifferentiated cells.
Therefore,all the given options are correct.

(A) In suspension culture,a rotary shaker is used for the following reasons:
$1$. $(i)$ Continuous agitation increases the surface area for gas exchange (oxygen and carbon dioxide) between the cells and the culture medium.
$2$. $(ii)$ It ensures that nutrients are uniformly distributed throughout the medium,preventing localized depletion.
$3$. $(v)$ The mechanical force of agitation helps in breaking down large cell aggregates into smaller,uniform cell clusters,which promotes better growth and nutrient uptake.
Sterilization $(iii)$ is a separate process performed before inoculation,and temperature $(iv)$ is usually maintained by the incubator environment,not by agitation itself. Thus,the correct statements are $(i), (ii),$ and $(v)$.

(B) In plant tissue culture,the induction of callus from an explant typically requires a controlled environment. The optimal temperature range for most plant species to initiate callus formation is generally between $20^o\, C$ and $25^o\, C$. Among the given options,$24^o\, C$ is the most suitable temperature for callus induction.

(C) In plant tissue culture,specifically suspension culture,the 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 is continuously agitated using a rotary shaker.
The standard speed for this agitation in a rotary shaker is typically maintained between $100$ to $250 \, rpm$ (revolutions per minute).
This agitation helps in the uniform distribution of nutrients and oxygen to the cells.

(D) Embryo culture is a technique used in plant tissue culture where an embryo is isolated from a seed and grown in a sterile nutrient medium. This method is particularly useful for seeds that exhibit dormancy or have low viability,as it allows the embryo to bypass the natural germination inhibitors or environmental requirements,leading to the development of plantlets.

(D) Plant tissue culture is a technique used to maintain or grow plant cells,tissues,or organs under sterile conditions on a nutrient culture medium of known composition. This method is widely used for the production of clones of plants,known as micropropagation,and is a fundamental tool in plant biotechnology.

(D) Embryo rescue is a technique in plant tissue culture used to assist the development of embryos that might otherwise fail to mature.
$1$. It is used to develop useful plant varieties by overcoming hybridization barriers,such as embryo abortion in wide crosses.
$2$. It is often employed in the creation of genetically modified plants where the transformation process might affect embryo viability.
$3$. It can also be used as part of rapid clonal propagation protocols to ensure the survival of valuable genotypes.
Therefore,all the mentioned purposes are valid applications of embryo rescue.

(A) In plant tissue culture,callus formation and maintenance are primarily regulated by the balance of plant growth regulators,specifically $Auxin$ and $Cytokinin$. $Agar-agar$ is a solidifying agent used to provide a physical support medium for the explant to grow. $Ethylene$ is a gaseous plant hormone primarily involved in fruit ripening,senescence,and stress responses,and it is generally not added to the culture medium for the induction or maintenance of callus.