Plant Growth & Regulation MCQ Quiz in मल्याळम - Objective Question with Answer for Plant Growth & Regulation - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is 3.

Explanation:

• The increase in growth per unit time is referred to as the plant growth rate.
• When we plot the increase in cell number (growth rate) against time, we get a typical S-shaped curve.
• This curve is known as the growth curve or sigmoid growth curve due to the sigmoid shape of the curve obtained.

The sigmoid growth curve has three phases of growth:

1. Lag phase: (initial or the beginning phase) It is mainly characterized by very slow growth.
2. Log phase: (Exponential phase) It is the middle phase of the system and is characterized by very fast and rapid growth of the plant body.
   • After initiation of growth, it increases rapidly at an exponential rate.
3. Stationary phase: (Steady phase) This phase occurs when the plant reaches maturity or the nutrient supply becomes limited.

• This curve shows a characteristic feature of living organisms growing in a natural environment.
• This curve is typical for all cells, tissues, and organs of a plant.

Key Points

• Plant Growth Regulators are used to externally regulate the plant physiological processes.
• Wine are produced by fermenting grapes.
• Gibberellins are frequently used on grapes to enlarge their size and induce seedlessness.
• This increases the wine yield and decrease production cost.
• Gibberellins are chemically terpenes.

Hence, the chemical nature of the PGR helpful in wine production is terpenes.

Additional Information

PGR are of different chemical natures:

Concept:

• The aleurone layer is a specialized layer of cells that surrounds the endosperm of cereal grains like maize, wheat, and barley.
• It is located between the endosperm and the seed coat.
• The aleurone layer is rich in proteins, lipids, and enzymes and plays an important role in seed germination.
• During germination, the aleurone layer synthesizes and secretes hormones that stimulate the breakdown of stored nutrients in the endosperm.
• In addition to its role in seed germination, the aleurone layer has also been found to be involved in plant defense against pathogens and pests.

Important Points

• The hormone secreted from the aleurone layer of maize seed during germination is gibberellic acid (GA).
• Gibberellic acid (GA) plays a crucial role in maize seed germination.
• During seed germination, the embryo produces GA, which stimulates the aleurone layer to synthesize and secrete more GA.
• The GA produced by the aleurone layer then diffuses into the endosperm and stimulates the breakdown of stored starch into simple sugars that can be used by the developing embryo.
• In addition to promoting starch breakdown, GA also stimulates the synthesis of hydrolytic enzymes like alpha-amylase, proteases and lipases.
• These enzymes further help in the breakdown of stored proteins, starches and lipids in the endosperm.
• This process releases nutrients that can be used by the growing embryo for energy and growth.
• GA also plays a role in promoting the elongation of the embryo axis and the development of shoot and root systems.
• It stimulates cell elongation and division in the embryo, leading to the growth of the shoot and root meristems.
• This process helps the emerging seedling to penetrate the soil and establish itself in the environment.
• Thus, gibberellic acid is an essential hormone for maize seed germination, promoting the breakdown of stored nutrients and the growth and development of the embryo and seedling.

The correct option is Hydathodes

Explanation: 

• Guttation is the process of loss of water in the form of droplets from the leaf margins or uninjured regions. It occurs when transpiration is low and water absorption is high i.e. the root pressure is high.
• The liquid that is exuded out through guttation contains organic and inorganic dissolved substances along with water, so the liquid is not pure water only.
• Guttation is seen in herbaceous plants like tomatoes, grasses, balsam, etc.
• The process of guttation occurs through minute specialized pores called Hydathodes or water stomata, these pores always remain in the open state.
• Generally, guttation takes place at midnight or early morning.

Additional Information

• Stomata - Water gets lost through stomata during transpiration.
• Loss of water in the form of vapours, from the aerial parts (organs) of living plants, is known as Transpiration.
• About 80-90% of transpiration occurs through stomata oly. 

The correct answer is Cambium.

Key Points

• Cambium is a layer of actively dividing cells located between the xylem and phloem tissues in plants.
• This layer is responsible for secondary growth, which increases the girth of stems and roots.
• The cells of the cambium divide and differentiate to form secondary xylem (wood) towards the inside and secondary phloem towards the outside.
• Cambium activity is seasonal in temperate regions, with growth rings forming as a result of variations in growth rate during different seasons.

Additional Information

• Primary Growth: This occurs at the tips of roots and shoots due to the activity of apical meristems, leading to an increase in length.
• Apical Meristem: These are the regions at the tips of roots and shoots where cells actively divide, contributing to the primary growth of the plant.
• Intercalary Meristem: Found at the base of leaves or internodes, especially in grasses, contributing to lengthening of these plant parts.
• Secondary Growth: This involves the thickening of stems and roots, occurring due to the activity of the vascular cambium and cork cambium.

Concept:

• Plant hormones or phytohormones are chemical compounds that control various developmental as well as physiological functions of a plant.
• They are produced by the plant and are functional at very low concentrations.
• The major plant hormones include - Auxin, Gibberellin, Cytokinin, Ethylene and Abscisic acid.

Important Points

• Auxin - 
  • It helps in cell elongation, growth and differentiation.
  • It is present mainly at the root and shoot apices.
  • It is responsible for the phenomenon of apical dominance, where the apical buds inhibit growth of lateral buds.
  • It results in increasing the height of a plant due to apical dominance.
  • It can also initiate root growth in stem cuttings.
  • It may also promote flowering and prevent early fruit drop.
• Cytokinin - 
  • It is mainly associated with cell division and is present in regions of rapid cell division.
  • It helps to overcome apical dominance and promote lateral shoot growth.
• Florigen - 
  • It is a proteinaceous hormone-like signal molecule that controls flowering in plants.
  • According to Chailakhyan (1936), it is a universal flowering hormone that helps in initiating flowering in plants.
  • It is believed to be synthesized in the leaves and transported to the shoot apical meristem, where it stimulates floral transition.
• Ethylene - 
  • It is a gaseous phytohormone produced in the tissues undergoing senescence.
  • It helps in fruit ripening and other senescence-related activities.
  • It breaks seed and bud dormancy to initiate germination in some species.
  • It also induces leaf epinasty under stress conditions.
  • The triple response of ethylene includes reducing rate of elongation, increasing lateral expansion and swelling of region below hook in seedlings.

Therefore, the correct answer is Ethylene.

Confusion Points

• Please note that there are 2 sets of information given in the question.
• The first set (options a-e) mentions the names of compounds.
• The second set (options 1-4) mentions the combinations of first set of options.

Key Points

• Auxin refers to a group of plant hormones that regulate plant growth.
• Based on their origin, auxins can be divided into:
  • Natural Auxins - They occur naturally in the plant and affect physiological functions. E.g. - IAA, IBA.
  • Artificial Auxins - These are synthetically-derived chemical compounds that resemble IAA in biological activity. E.g. - NAA.
• Artificial auxins are widely used in horticultural practices, as weedicides, rooting agents and defoliating agents.

Important Points

• IPA
  • Indole-3-pyruvic acid (IPA) is an intermediate in the IAA biosynthesis pathway.
  • Hence, it is not an artificial auxin.
• PAA
  • Phenylacetic acid (PAA) is a natural auxin.
• NAA
  • Naphthalene acetic acid (NAA) is a artificial auxin that is used as a rooting agent.
• 2,4,5-T
  • 2,4,5 - Trochlorophenoxyacetic acid is an artificial auxin that is used as a herbicide.
• 2,4-D
  • 2,4 - Dichlorophenoxy acetic acid (2,4-D) is a artificial auxin that is widely used as a herbicide.
• Thus the answer will be (c), (d) and (e).

Explanation-

• Auxins refer to a group of plant growth hormones or regulator (PGR).
• Auxin (from Greek ‘auxein’ : to grow) was first isolated from human urine.
• The term ‘auxin’ is applied to the indole-3-acetic acid (IAA), and to other natural and synthetic compounds having certain growth-regulating properties.
• Seedless fruits are called parthenocarpic fruit which can be produced by a spray of auxin(IAA).

Therefore statement 1 is CORRECT.

• Fruits are the results of fertilization, there are a few species in which fruits develop without fertilization. Such fruits are called parthenocarpic fruits.
• Such fruits are seedless.

Therefore statement 2 is CORRECT.

• Gibberellins are another kind of promoter PGR.
• There are more than 100 gibberellins reported from widely different organisms such as fungi and higher plants.
• They are denoted as GA1, GA2, GA3, and so on.
• Gibberellins, Auxin, etc. are effective in producing parthenocarpic fruit.

Therefore statement 3 is INCORRECT.

• Fruits are the results of fertilization, there are a few species in which fruits develop without fertilization. Such fruits are called parthenocarpic fruits.

Therefore statement 4 is CORRECT.

The correct answer is Peroxyacetyl nitrate.

Explanation:

• Peroxyacetyl nitrate are a phytotoxic air pollutant produced by the reaction of nitrogen oxides and hydrocarbons in the presence of light. 
• This pollutant can inhibit plant growth in both closed ecosystems and in the field.

Key Points

• Plant growth regulators are also known as Plant growth substances, phytohormones, and plant hormones.
• These are the small, simple organic molecules of the diverse chemical composition produced naturally in higher plants that control the growth and other physiological functions.
• These are required in a very small amount by the plant.
• Five main natural plant growth regulators are auxins, gibberllins, cytokinin, ethylene, and Abscisic acid (ABA).
  • Auxin: It controls cell division and xylem differentiation.
  • Gibberellin: It helps in elongation of the internodes so as to increase the height of the plant.
  • Cytokinin: It helps in the growth of lateral buds and overcome apical dominance.
  • Abscisic acid: It gives signal for closure of stomata in plants to prevent water loss during water stress.
  • Ethylene: It is highly effective in fruit ripening.

Key Points

• Apoptosis is a form of programmed cell death or cellular suicide
• Apoptosis is an orderly process in which the cell’s contents are packaged into small packets of membrane for digestion by immune cells.
• They shrink and develop blebs on their surface
• The DNA in the nucleus, organelles, and endoplasmic reticulum, break down into fragments
• In the end, the entire cell splits up into small chunks, each neatly enclosed in a package of membrane
• Apoptotic cells release signals that attract debris-eating (phagocytic) immune cells, such as macrophages
• Fragments of the dying cell display a lipid molecule called phosphatidylserine on their surface
• Phosphatidylserine is usually hidden on the inside of the membrane
• Caspases, a unique family of cysteine proteases, execute programmed cell death (apoptosis) 
• Apoptosis removes cells during development, pest attack, cancerous cells etc.

Additional Information

• Necrosis 
  • When cells are damaged by harmful factors (such as injury or toxic chemicals), they undergo necrosis and die
  • Damaged cell’s plasma membrane can no longer control the passage of ions and water
  • The cell swells up, and its contents leak out through holes in the plasma membrane
  • This often causes inflammation in the tissue surrounding the dead cell
  • It is not orderly and is caused by external harmful factors
• Senescence
  • Biological aging is the gradual deterioration of functional characteristics in living organisms
  • Senescence is a cellular response that limits the proliferation of aged or damaged cells
• Abscission
  • Natural detachment of parts of a plant, typically dead leaves and ripe fruit
  • Removal of a part of a plant by killing the cells around the joint
  • A protective layer or scar tissue forms at the point of detachment
  • It prevents the entry of pathogen and protects the inner tissues from desiccation
  • Ethylene promotes abscission