System Physiology Plant MCQ Quiz in తెలుగు - Objective Question with Answer for System Physiology Plant - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

The correct answer is A‐II, B‐III, C‐IV, D‐I

Explanation:

I. Frankia

• Frankia is a genus of nitrogen-fixing actinobacteria.
• These bacteria form symbiotic associations with actinorhizal plants, which are non-leguminous woody plants.
• Frankia bacteria live in root nodules of actinorhizal plants, where they convert atmospheric nitrogen (N₂) into ammonium (NH₄⁺), which the host plant can use for growth.
• Examples of Host Plants are alder (Alnus), bayberry (Myrica), and sweetfern (Comptonia).

II. Azorhizobium

• Azorhizobium is a genus of nitrogen-fixing bacteria closely related to Rhizobium.
• Azorhizobium forms symbiotic relationships with legumes.
• These bacteria colonize the roots of leguminous plants, forming nodules where they fix atmospheric nitrogen into a form that plants can assimilate, thereby enhancing soil fertility and plant growth.
• Examples of Host Plants are various leguminous plants, notably those in aquatic or semi-aquatic environments, such as Sesbania rostrata.

III. Anabaena

• Anabaena is a genus of filamentous cyanobacteria (also known as blue-green algae).
• Anabaena forms a mutualistic symbiotic relationship with the aquatic fern Azolla.
• In this symbiosis, Anabaena fixes atmospheric nitrogen into ammonia which benefits the host plant. In return, the cyanobacterium gains a protective environment and access to photosynthetic products from the plant.
• Examples of host plants are water fern Azolla.

IV. Acetobacter

• Acetobacter is a genus of acetic acid bacteria known for their ability to fix nitrogen and oxidize ethanol to acetic acid.
• Acetobacter diazotrophicus is a species known for its nitrogen-fixing capability associated with sugarcane.
• These bacteria live endophytically in sugarcane and other plants, fixing atmospheric nitrogen, which assists plant growth without forming visible nodules.
• Examples of host plants are sugarcane and other tropical grasses.

The correct answer is Option 3 i.e. Flowering is not altered under normal growth conditions in plants defective in vernalization.

Explanation-

Genetic and physiological studies of the vernalization pathway in Arabidopsis have identified some of the genes that are involved in this process. Vernalization involves epigenetic changes in the expression of gene, FLC (flowering locus C).

Vernalization is a key physiological process in certain species of plants characterized by the necessity of an extended period of cold temperatures to trigger the transition from vegetative growth to flowering. This process is key to ensuring that seeds germinate and grow at the optimal time such that flowers will bloom in appropriate conditions, typically spring or summer

A.Vernalization causes a stable change in the competency of the meristem to form an inflorescence in some plant species.

• This statement is correct. Vernalization involves a period of prolonged cold or winter conditions, which induces a change in some plants that is necessary for the subsequent development of flowers.

B.Vernalization causes changes in gene expression that do not involve an alteration in the DNA sequence.

• This statement is correct. Vernalization involves changes to the epigenetic state of the chromatin, specifically, methylation of histones that influences gene expression. These changes do not involve altering the DNA sequence itself.

C.Flowering is not altered under normal growth conditions in plants defective in vernalization.

• This is incorrect. In plants where the vernalization process is defective, the timing of the flowering can be significantly impacted, even under normal growth conditions. For instance, in some biennial and perennial plants, flowering does not occur until the plant has been exposed to the extended period of cold temperatures necessary for vernalization. Without this process, these plants may fail to flower at all.

D.Vernalization alters the expression of the FLC gene.

• This statement is correct. In Arabidopsis, a species often used as a model organism in plant biology, FLOWERING LOCUS C (FLC) is a key plant that represses flowering. Vernalization leads to the downregulation of FLC, lifting its repression, and thus allowing the plant to flower. FLC gene encodes a MADS-box transcription factor that represses flowering. Cold exposure induces changes in the chromatin of FLC, leading to its repression, and enables plants to flower. This suppression is mitotically stable and remains even after the plant returns to warmer temperatures, allowing the flowering process to occur at the right time.

Conclusion- So,the incorrect statement is Flowering is not altered under normal growth conditions in plants defective in vernalization.

The correct answer is Option 4 i.e.Degradation of guardee protein can activate the defense response.

Explanation-

In plant-pathogen interactions, plants rely on their immune system to defend against invading pathogens. The guardee model is an important part of understanding this interaction. According to this model, certain plant proteins, known as R proteins, guard or monitor other key host (plant) proteins, named guardees, that are targets of pathogen effectors. When a pathogen effector modifies the guardee protein, the R protein 'notices' this change and initiates a defense response, often leading to a form of programmed cell death called the hypersensitive response that prevents the pathogen from spreading.

Key Points "Guardee" is a term used in plant immunology to describe a plant protein that is monitored or 'guarded' by a resistance (R) protein. The R protein is a part of the plant's immune system and may also be referred to as a 'guard.'

• The guardee and guard proteins play significant roles in protecting the plant during pathogen infections, particularly in the context of Pathogen-associated molecular pattern (PAMP)-triggered immunity and effector-triggered immunity (ETI).
• PAMP-triggered immunity: PAMPs are molecules associated with groups of pathogens recognized by cells of the innate immune system. In response to PAMP recognition, a signaling cascade triggers defensive measures like the production of antimicrobial compounds.
• Effector-triggered immunity: While PAMP-triggered immunity provides a generic defense, it's often overcome by pathogens that deliver effectors into host cells to manipulate host processes in ways favorable to the pathogen. ETI is then activated wherein specific R proteins recognize these pathogen effectors or their actions on the guardee proteins.The pathogen, which is trying to infect the plant cell, produces specific effector proteins that are delivered into a host cell. Effector proteins interfere with the host's defenses and can bind to, or otherwise modify, the behavior of the guardee proteins.

Fig-Guard hypothesis the plant R proteins (guard) are associated with the endogenous host protein (guardee) which are common target proteins for the pathogens. The interaction of effector pathogen proteins with the host proteins, causes a change in their structure which is then recognized by the guard proteins. As a result, a pathogen response signaling cascade is triggered against the microbial evasion. 

This modification to the guardee proteins alerts the R proteins that something is wrong. Upon detection of an effector's action, R proteins initiate the plant's defenses. Such defenses can include a localized inflammation, the production of antimicrobial metabolites, and a form of programmed cell death in the area around the site of infection known as hypersensitive response, which can limit the pathogen's ability to spread.

Conclusion-Thus, when a guardee protein is modified or degraded by the actions of a pathogen, it can activate the plant's defense response, limiting the spread of the pathogen and maintaining the health of the plant as much as possible.

Concept:

• Aquaporins are categorized into several different types based on their structural conformation and the type of molecules they transport.
• They are grouped into four main homologous subfamilies, particularly in plants:
• Plasma membrane Intrinsic Protein (PIP): This is the most researched type of aquaporin, typically found in the plasma membrane of cells.
• They play a crucial role in regulating water transport in response to changing environmental conditions.
• Tonoplast Intrinsic Protein (TIP): These are located in the tonoplast (the membrane surrounding the vacuole, an intracellular compartment in plant cells), where they contribute to regulating water transport into and out of the vacuole.
• Nodulin-26-like Intrinsic Protein (NIP): Found in leguminous plants, they were first identified in the symbiotic root nodules of soybeans. They can transport water and other small molecules.
• Small basic Intrinsic Protein (SIP): This is a smaller subfamily of aquaporins found in the endoplasmic reticulum.
• Additionally, in humans and other mammals, specific types of aquaporins have been identified:
• Aquaporin-0: (AQP0) Found in the eye lens, where it plays a crucial role in maintaining transparency and refractive index.
• Aquaporin-1: (AQP1) Present in many tissues, including the kidney and red blood cells; it facilitates water transport across cell membranes.
• Aquaporin-2, -3, -4: (AQP2, AQP3, AQP4) Predominantly found in the kidney, they help in the regulation of water balance.
• Aquaporin-5: (AQP5) Located in the salivary, lacrimal (tear), and sweat glands, participating in fluid secretion.
• Aquaglyceroporins (such as AQP3, AQP7, AQP9, AQP10): Besides transporting water, these proteins also transport other small, uncharged molecules, such as glycerol. They are especially important for metabolic processes.
• Aquaporins are a class of integral membrane proteins that facilitate water transport across cell membranes.
• These proteins form pores or channels in the membranes, allowing millions of water molecules to pass through each second.
• This rapid water transport is vital in tissues that require high rates of water permeability, and these proteins can be found abundantly within a diverse range of organisms from bacteria to humans, and especially so in plants.
• In addition to facilitating water transport, some specific aquaporins, known as 'aquaglyceroporins,' also permit the transport of other small, uncharged molecules such as glycerol, urea, ammonia (NH3), and carbon dioxide (CO2).
• Aquaporin activity is regulated by a series of complex mechanisms, including phosphorylation, where a phosphate group is added to the protein, modifying its function.
• This regulation can control the distribution of aquaporins between intracellular storage and the plasma membrane, or influence the individual aquaporin channel's state.
• Other regulatory factors include intracellular calcium concentration and reactive oxygen species (ROS), both of which can influence aquaporin activity by affecting their phosphorylation state or other signals controlling their trafficking within the cell.

Explanation:

Statement: A. Aquaporins form water channels in the membrane. This is generally true. Aquaporins are integral membrane proteins that function as channels in the cellular lipid bilayer, primarily facilitating the transport of water between cells.

Concept:

• Heat stress events are major factors limiting crop productivity.
• During summer, land plants must anticipate in a timely manner upcoming mild and severe temperature.
• They respond by accumulating protective heat-shock proteins (HSPs), conferring acquired thermotolerance.
• All organisms synthetize HSPs; many of which are members of the conserved chaperones families.
• An unclear cellular signal activates HSFs, which act as essential regulators.
• In particular, the HSFA (Heat Shock Transcription Factor) subfamily can bind heat shock elements in HSP promoters and could mediate the dissociation of bound histones, leading to HSPs transcription.
• HSP chaperones prevent, use, and revert the formation of misfolded proteins, thereby avoiding heat-induced cell death.
• Remarkably, the HSP20 family is mostly tightly repressed at low temperature, suggesting that a costly mechanism can become detrimental under unnecessary conditions.

Explanation:

•  The increase in temperature increases the fluidity of the plasma membrane, resulting in the activation of CNGCs ( cyclic nucleotide-gated channels ) heat sensors.
• Transient periplasmic Ca2+ entry into the cytosol trigger is an unknown signaling cascade that activates HSFA1.
• Excessive temperatures are expected to denature heat-labile proteins in the cytosol.
• Misfolded and aggregated proteins are assumed to recruit the HSP90 and HSP70 being in part bound to HSFA1.
• The dissociation of HSP70-90 is a key step that leads hyperphosphorylation of HSFA1 by CBK3 and leads to its translocation into the nucleus to bind HSEs.
• HSFA1 might mediate a signal to the chromosome remodeling machinery to remove bound histones from HSP genes.
• HSFA1 can also activate histone and DNA modifications required for the regulatory responses of HSPs.
• RNA polymerase II is then recruited for the transcription of HSFA2 (red circle), forming a superactivator complex with HSFA1 and leading to accumulation of HSPs, ultimately conferring acquired thermotolerance in land plants.

Fig 1: Mechanism of heat tolerance in plants

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The correct answer is Option 4 i.e.Both large and small subunits in chloroplast. 

Key Points

• Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) enzyme is an important enzyme in the plant kingdom.
• It catalyses the rate-limiting step in the Calvin cycle. 
• It is present in large amount in plant cells due to its slow catalysing activity and its lower substrate specificity.
• It consitiutes 30-40% of the total soluble proteins in the C3 plant.
• Oxygen molecule is another substrate that competes with carbon dioxide for reaction with ribulose 1,5-bisphosphate. 
• Rubisco catalyzes a non-productive oxygenation reaction which results in the production of 2-phosphoglycolate (2PG), which is a toxic compound that is recycled by plants in an energy-wasteful process termed photorespiration.
• Oxygen and carbon dioxide binds to the same active site in the Rubisco.

Explanation:

• Rubisco is a hexadecamer enzyme that is composed of 8 large subunits and 8 small units.
• The larger subunits of the Rubisco are universally synthesised in the chloroplast. Hence, large subunit of Rubisco is synthesised in the chloroplast of the red and brown algae as well as green plants and green algae.
• The smaller subunits of the Rubisco is synthesized in the nucleus in the case of green plants and green algae while it is synthesised in the chloroplast in the case of red and brown algae.
• So, the case of red and brown algae all the subunits of the Rubisco (8 large and 8 small subunits) are synthesized in the chloroplast.

Hence, the correct answer is Option 4.

The correct option is: 3

Explanation:

• Auxin is a plant hormone that plays a key role in promoting cell elongation, particularly in young shoot tissues. It is involved in various aspects of plant growth, including phototropism (growth toward light) and gravitropism (growth in response to gravity). Auxin promotes elongation by loosening the cell walls, allowing cells to expand.
• Abscisic acid is involved in stress responses, such as drought tolerance, and helps in the closure of stomata, but it does not promote cell elongation.
• Cytokinin promotes cell division and can delay aging in plant tissues, but it does not primarily promote cell elongation.
• Ethylene is involved in fruit ripening, leaf abscission, and responses to stress but does not promote cell elongation. In fact, it can inhibit elongation in certain contexts.
• Auxin is synthesized mainly in the apical meristem of plants and then transported downward, where it regulates growth. The gradient of auxin concentration in plant tissues is essential for proper growth and development.

 The correct answer is A, D, and E.

Explanation:

Crassulacean Acid Metabolism (CAM) is an adaptation in certain plants, allowing them to conserve water by opening their stomata at night to capture CO₂ and close them during the day. 

Statement A: "The HCO₃⁻ concentration is enriched in the cytosol during the night by the CO₂ coming from the external atmosphere through the open stomata and the mitochondrial respiration."

• This is correct. At night, CAM plants open their stomata to take in CO₂, which is converted to bicarbonate (HCO₃⁻) in the cytosol. CO₂ is also generated from mitochondrial respiration.

Statement B: "Oxaloacetate produced by the action of PEPCase is stored in the vacuole during dark."

• This is incorrect. Oxaloacetate is not stored directly in the vacuole. Instead, it is rapidly converted into malate, which is stored in the vacuole during the night.

Statement C: "During light, oxaloacetate produces malate that provides CO₂ for the Calvin Benson cycle in the chloroplast."

• This is incorrect. During the day, malate (stored during the night) is decarboxylated to release CO₂, which then enters the Calvin-Benson cycle in the chloroplast. Oxaloacetate itself is not directly involved in this process during the day.

Statement D: "During dark, phosphoenolpyruvate is produced by the breakdown of starch present in the chloroplast."

• This is correct. During the night, starch is broken down to produce phosphoenolpyruvate (PEP), which is used by PEP carboxylase (PEPCase) to fix CO₂ into oxaloacetate.

Statement E: "CAM is a mechanism of concentrating CO₂ around Rubisco by keeping stomata closed during the day."

• This is correct. CAM plants concentrate CO₂ around Rubisco during the day by decarboxylating malate when the stomata are closed, thus reducing water loss.

Key Points

• HCO₃⁻ is enriched in the cytosol at night when the stomata are open.
• Malate, not oxaloacetate, is stored in the vacuole during the night and provides CO₂ during the day for the Calvin-Benson cycle.
• Phosphoenolpyruvate (PEP) is produced at night by the breakdown of starch.
• CAM plants close their stomata during the day, concentrating CO₂ around Rubisco to reduce water loss.

Fig. CAM Plant

The correct answer is Reducing sugars.

Explanation:

1. Reducing Sugars: These sugars, such as glucose and fructose, have free aldehyde or ketone groups that can participate in oxidation-reduction reactions. While they can be transported in the phloem, they are less stable over long distances due to potential for oxidation and involvement in Maillard reactions. As a result, they are not the primary form of carbon transported in the phloem.

2. Mannitol: This is a sugar alcohol that can be transported in the phloem and is stable over long distances. It is used by some plants as an osmotic agent and can help with water retention, making it suitable for transport.

3. Galactosyl-sucrose Oligosaccharides: These are forms of non-reducing sugars and are commonly found in the phloem sap. They are stable and effective for long-distance transport of carbon because they do not have reactive groups that can lead to degradation.

4. Non-reducing Sugars: These sugars, like sucrose, are preferred for long-distance transport in phloem because they are stable and do not readily participate in reactions that can lead to loss of carbon or energy.

Conclusion:

While reducing sugars can be transported, they are not ideal for long-distance transport due to their instability. In contrast, non-reducing sugars and stable compounds like mannitol and oligosaccharides are more suited for this function.

Thus, the correct answer is Reducing sugars.