Plant Growth and Development MCQ Quiz - Objective Question with Answer for Plant Growth and Development - Download Free PDF

The correct answer is 1) A, B, C only

Concept:

• Plant growth and development are regulated by various plant growth regulators (PGRs) such as auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These regulators can either promote or inhibit plant growth depending on their type and concentration.
• Processes like parthenocarpy, dedifferentiation, and redifferentiation are fundamental aspects of plant development.
• Understanding the roles of PGRs and the processes involved in plant growth is critical to solving the given question.

Explanation:

• A. Parthenocarpy can be induced by auxins: Parthenocarpy is the development of fruit without fertilization, leading to seedless fruits. Auxins, along with gibberellins, can artificially induce parthenocarpy by mimicking the hormonal changes that occur after fertilization. This statement is correct.
• B. Plant growth regulators can be involved in promotion as well as inhibition of growth: Plant growth regulators such as auxins, gibberellins, and cytokinins promote growth, while others like abscisic acid and ethylene can inhibit growth. Thus, PGRs can have dual roles depending on the physiological context. This statement is correct.
• C. Dedifferentiation is a pre-requisite for redifferentiation: Dedifferentiation refers to the process where mature cells regain the ability to divide and form callus tissue. These dedifferentiated cells can then undergo redifferentiation to develop into specific tissues or organs. This is an essential step in plant tissue culture. This statement is correct.

Incorrect Statements:

• D. Abscisic acid is a plant growth promoter: This statement is incorrect. Abscisic acid (ABA) is primarily a growth inhibitor. It plays a significant role in stress responses such as closing stomata during water stress and inducing dormancy in seeds and buds. It is not a growth promoter.
• E. Apical dominance promotes the growth of lateral buds: This statement is incorrect. Apical dominance refers to the suppression of lateral bud growth due to the activity of the apical bud, which produces auxins. This phenomenon inhibits the growth of lateral buds rather than promoting it.

Summary:

• The correct statements are A, B, and C, which are included in option 1.
• Statements D and E are incorrect because abscisic acid is a growth inhibitor, and apical dominance suppresses rather than promotes lateral bud growth.

The correct answer is Cytokinin

Concept:

• Phytohormones are chemical substances produced in plants that regulate various physiological processes. Key phytohormones include auxins, cytokinins, gibberellins, ethylene, and abscisic acid.
• Cytokinins are plant hormones primarily involved in promoting cell division (cytokinesis) in roots and shoots. 
• Cytokinins help overcome the apical dominance. They promote nutrient mobilisation which helps in the delay of leaf senescence.
• Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits etc.
• It helps to produce new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoot formation.

Other Options:

• Ethylene: Ethylene is a gaseous plant hormone primarily involved in promoting fruit ripening and leaf abscission (shedding). It accelerates leaf senescence rather than delaying it.
• Abscisic Acid: Abscisic acid (ABA) is known as the "stress hormone" in plants. It plays a role in stomatal closure, seed dormancy, and stress responses. ABA generally induces senescence rather than delaying it.
• Gibberellin: Gibberellins are involved in promoting stem elongation, seed germination, and flowering.

The correct answer is d → a → c → b

Explanation:

• The life cycle of a typical dicot plant involves various stages of cell differentiation and development. Meristematic cells initially divide and differentiate into various cell types and tissues that form the plant body.

1. Divisions in primary meristem (d): This is the first step. The primary meristem is responsible for the initial growth and divisions that lead to the formation of various tissues in the plant.
2. Differentiation (a): This follows the divisions in the primary meristem. The cells produced from meristematic divisions undergo differentiation to become specialized cells and tissues with distinct functions.
3. Dedifferentiation (c): This occurs when differentiated cells regain the ability to divide and revert to a less specialized state, often forming secondary meristems or callus tissue under certain conditions.
4. Redifferentiation (b): This is the final step, where dedifferentiated cells undergo another round of differentiation to form new specialized tissues and organs.

The correct answer is Maize

Explanation:

• Heterophylly refers to the occurrence of different types of leaves on the same plant. It can be observed in various forms such as environmental heterophylly, developmental heterophylly, and heterophylly due to the phase of life.
• Heterophylly due to the phase of life indicates that juvenile and mature stages of the plant have leaves with different shapes and structures.
• This is a common phenomenon observed in certain plant species as they grow and transition through different stages of their life cycle.
• Plants follow different pathways in response to environment or phases
  of life to form different kinds of structures. This ability is called plasticity, e.g., heterophylly in cotton, coriander and larkspur.
• Cotton, coriander, and larkspur: These plants exhibit heterophylly due to the phase of life. The leaves in juvenile plants are morphologically different from those in mature plants. This adaptation helps the plant to optimize its growth and survival at different stages of its life cycle.
• Buttercup only: Buttercup exhibit difference in shapes of leaves produced in air and those produced in water.

The correct answer is A: Plasmatic growth, B: Differentiation, C: Expansion, D: Maturation

Explanation:

• Development is a term that includes all changes that an organism goes through during its life cycle from germination of the seed to senescence. Diagrammatic representation of the sequence of processes which constitute the development of a cell of a higher plant is given in Figure
• It is also applicable to tissues/organs.

Fig: Sequence of the developmental process in a plant cell

The correct answer is All the Above.

Key Points

•  Hormones are regulatory substances produced in an organism.
•  Different plant hormones help to coordinate growth, development, and responses to the environment.
•  Auxin hormone - It synthesizes at the shoot tip of the plant and helps the cells to grow longer.
•  Gibberellins hormone - It helps in the growth of the stem.
•  Cytokinin hormone - It promotes cell division.
•  Auxin, Gibberellins, and Cytokinins are examples of Plant growth hormones.
•  Abscisic acid - It is a type of hormone which signals to stop growth.

 Additional Information

•  Ethylene Hormone- This hormone is a critical regulator of plant growth and development. It is best known for its effect on fruit ripening and organ abscission.

Concept-

• Plant growth hormones or phytohormones are simple molecules with complex chemical composition, that regulates the growth and physiology of plants.
• Based on their functions on the living plant body, they can be classified into two groups-
  • Plant growth promoters - Eg. Auxins, Gibberellins & cytokinins.
  • Plant growth inhibitors -Eg. Abscisic acid.
• Gaseous PGR like ethylene can be put into both groups, however, it is largely an inhibitor of growth activities.

Key Points

The sub-apical elongation in plants is induced by Gibberellins.

• Gibberellins are plant growth hormones.
• It stimulates elongation of the stem, flowering, and germination.
• Gibberellin is a diterpenoid.
• There are more than 100 gibberellins reported from widely different organisms such as fungi and higher plants.
• They produce a wide range of physiological responses in plants.
• Their ability to cause an increase in length of the axis is used to increase the length of grapes stalks.

Additional Information

Auxins

• Auxins (from Greek ‘auxein’ to grow) were 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.
• They are generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action.
• Auxins like IAA and indole butyric acid (IBA) have been isolated from plants.
• NAA (naphthalene acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic) are synthetic auxins.
• All these auxins have been used extensively in agricultural and horticultural practices.

Cytokinins

• Cytokinins have specific effects on cytokinesis and were discovered as kinetin (a modified form of adenine, a purine) from the autoclaved herring sperm DNA.
• Kinetin does not occur naturally in plants.
• Search for natural substances with cytokinin-like activities led to the isolation of zeatin from corn kernels and coconut milk.
• Since the discovery of zeatin, several naturally occurring cytokinins, and some synthetic compounds with cell division promoting activity, have been identified.
• Natural cytokinins are synthesized in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits, etc.

Ethylene

• Ethylene is a group of plant growth regulators which are widely used for ripening fruits.
• It is also used for the production of more flowers and fruits.
• Ethylene is also used in agriculture practices to ripen fruits, germinate seeds.
• It is a gaseous hormone that stimulates transverse or isodiametric growth but retard longitudinal one.
• Ethylene is regarded as a multifunctional phytohormone that regulates both growth and senescence.
• It promotes or inhibits growth and senescence processes depending on its concentration, timing of application, and the plant species. 

Correct answer: 4)

Concept:

• Plasticity is defined as the ability of an organism to change its phenotype concerning a different environment.
• Plasticity also affects the morphology and physiology of an organism.

Explanation:

• In plants, plasticity forms different types of structures in response to the environment.
• Heterophylly is a common example of plasticity.
• Heterophylly is the formation of different types of leaf forms according to environmental conditions.
• For example, coriander, and cotton have leaves in the juvenile phase which are very much different from the matured plant leaves.​
• So, the correct answer is option 4.

Concept: 

• ‘Auxin’ is applied to the indole-3-acetic acid (IAA), and to other natural and synthetic compounds having certain growth regulating properties.
• It also helps to initiate rooting in stem cuttings.

Explanation:

• Synthetic auxins are used as weedicides.

Option 1:

• IBA (indole butyric acid ) is natural auxin.
• It plays a major role in inducing adventitious roots in stem cuttings. 
• Therefore, this is the incorrect option.

​Option 2:

• IAA (Indole acetic acid) is also natural auxin.
• It plays a major role in the elongation of plants and their development. 
• Therefore, this is the incorrect option.​

Option 3:

• NAA (Naphthalene acetic acid) is a synthetic auxin.
• It initiates the rooting process.
• It is also useful in plant tissue culture. 
• Therefore, this is the incorrect option.​

Option 4:

• 2, 4-D (2, 4-dichlorophenoxyacetic) is synthetic auxin. 
• 2,4-D is widely used to remove broad-leaved weeds or dicotyledonous weeds in cereal crops or monocotyledonous plants.
• It is also used to prepare weed-free lawns by gardeners. 
• Therefore, the correct answer is option 4.​​

Concept:

• Plant growth regulators (PGRs) also called phytohormones are small, simple molecules of different chemical compositions.
• There are two categories of PGRS: one that promotes growth, cell division, formation of flowers, fruits, seeds, etc., and other categories of PGRs promote wound healing and response to stress in plants.

Explanation:

Different plant growth regulators are:

• Auxins
  • Indole 2-Acetic Acid (IAA) is a type of Auxins.
  • Auxins help in root initiation in stem cuttings, promote flowering, and prevent fruit, and leaf drop in the early stages of plant growth.
• Gibberellins
  • The most common gibberellin used is Gibberellic acid (GA3).
  • They are used to increase the length of the axis (grapes), length of stem (sugarcane), elongation, and improvement in the shape of fruit (apple), and bolting (beetroot, cabbage). 
• Cytokinin
  • Natural cytokinin is synthesized in the sites of rapid cell division like root apex, shoot buds, and young fruits.
  • They help in overcoming apical dominance and delay in leaf senescence.
• Ethylene
  • It is a gaseous PGR. It plays a major role in the senescence and abscission of leaves and flowers.
  • It also helps in early fruit ripening.
  • Ethephon is commonly used ethylene it promotes female flowering in cucumber and helps in improving the yield.

So, the correct answer is option 4.

Concept:

• Plant growth regulators or plant hormones or phytohormones are small and simple chemical substances that control growth and differentiation of different plant cells.
• They can be classified into two groups based on their function:
  • Plant growth promoters - promote activities like cell division, cell growth, flowering, fruiting, seed formation, tropic growth etc.
  • Plant growth inhibitors - promote activities like dormancy and abscission.
• The five major plant hormones are-
  • Auxin
  • Cytokinins
  • Gibberellins
  • Ethylene
  • Abscisic acid​

Important Points

Indole Acetic Acid - 

• Indole Acetic Acid is the main Auxin present in the plants and is a plant growth promoting hormone.
• Auxins is majorly produced in the apices of stem and root and help in elongation.
• It plays an important role in cell division and differentiation by enhancing them.
• Auxins are also play a role in promoting flowering.
• Auxins are responsible in the maintenance of apical dominance
• It inhibits the growth of lateral (axillary) buds and promotes the growth of the apical buds.
• Auxins are widely used in vegetative propagation as it is used to initiate rooting in the stem cuttings.
• Indole acetic acid is sprayed on plants to stop premature fall of leaves, flowers and fruits in apple trees.

Additional Information

• Gibberellins - 
  • Gibberellins is a plant growth promoting hormone.
  • This hormone is responsible for the increase in length of the stem axis.
  • This is used to increase the length of the grape stalks in agriculture.
• Ethylene - 
  • It is a simple gaseous plant growth regulator.
  • It is produced by the tissues which are undergoing senescence and ripening fruits.
  • It is used to break the dormancy of seeds and buds.
  • Initiates germination in seeds (e.g. - peanut), sprouting of potato tubers etc.
  • It is majorly used for ripening the fruits.
• Benzyl amino purine - 
  • Benzyl amino purine is a synthetic cytokinin.
  • It is majorly used to induce sprouting and also shoot initiation in plant materials.
  • Cytokinins are the hormones which promote cell division activity.
  • Cytokinins are naturally synthesized in the regions where rapid cell division occurs like root apices, developing shoot buds etc.

Concept:

• Plant hormones or phytohormones are plant growth regulators that regulate the growth, development, reproduction, and death of the plant.
• There are different plant hormones such as ethylene, auxin, cytokinin, gibberellin, abscisic acid, etc.
• Coconut water represents the endosperm that is undergoing free-nuclear divisions, which is a type of cell division in which the nucleus divides multiple times before cell wall formation.

Explanation:

Option 1:

• Abscisic acid (ABA) is known as the stress hormone.
• It closes the stomata, causes abscission of plant organs, plant growth inhibitor, promotes dormancy, and works antagonistically to gibberellic acid/gibberellin.

Option 2:

• Auxin is another plant hormone. IAA (indole acetic acid) is a naturally occurring auxin.
• It is important in apical dominance, cell differentiation, elongation, tissue differentiation, etc.

Option 3:

• Cytokinin is another plant hormone that regulates plant growth and development.
• It promotes cell division, formation of leaves, formation of chloroplast, delays the process of senescence, etc.
• Zeatin is a hormone that belongs to the cytokinin family. It was discovered from corn Zea.
• The cytokinin in coconut water helps in the free-nuclear divisions of the endosperm that is taking place.

Option 4:

• Gibberellin is a plant growth regulator that has many physiological effects.
• Gibberellin plays a role in flowering, increases the length of the internode, delays senescence, and promotes rosette formation in cabbages.

Hence, the correct answer is option 3, Cytokinin.

Concept:

• As plants are sessile in nature, so to compensate for this and to deal with the rapid changes in the environment, they have developed growth responses.
• Plants therefore, alter their growth so they can grow into more favorable conditions. This is done by plant movement.
• Plant movements - the changes in the spatial orientation or conformation of an organ or its parts.
• Plants exhibit two types of movements:
  • Tropic - When a plant exhibits some growth movement in response to a stimulus, it is referred to as Tropic movement/ tropism.
  • Nastic - Movements which are non-directional responses to the stimuli and are independent to the direction of stimulus, are referred to as Nastic movements.
• So, tropic movement is a response to a stimulus that is particular to the direction of the stimulus in which the plants can respond to stimuli positively or negatively.
• When the movement is in the direction of the stimuli, it is Positive tropism; when the movement is away from the stimuli, it is Negative tropism.

Important Points

• ​Phototropism:
  • The type of tropism in response to light in which the plants can grow towards or away from the light.
  • As the stem grows towards the direction of light, it is positive phototropism while the roots grow away from light showing negative phototropism.
• Chemotropism:
  • The movement of the plant part towards a chemical stimulus.
  • Example: The growth of the pollen tube through the style is guided by the chemical secreted by the cells lining the style.
  • Also, within the ovary the pollen tube moves toward the egg because of the chemical cues provided by the degenerating synergids.
• Thigmotropism/ Haptotropism:
  • Touch / friction generated responses shown by the plants.
  • Tendrils and twiners are examples of this type of movement.
• Hydrotropism:
  • The movement of plants occurring due to the stimulus of water.
  • Example: The roots grow towards the area where water is present and shows positive hydrotropism.
• Geotropism/ Gravitropism:
  • The movement of plant parts in response to gravity.
  • Example: stems show negative geotropism while roots show positive geotropism.
• Thermotropism:
  • The growth movement of plants regulated by temperature.
  • A common example is the curling/ bending  of the leaves of Rhododendron plant in response to cold temperature.

So, when a pea tendril comes in contact of a string, it coils around it, it shows thigmotropism.

Concept:

• Plant growth regulators (PGRs) are defined as small, simple molecules of diverse chemical composition.
• They are also described as plant hormones or phytohormones.
•  PGRs are classified into two broad groups based on their functions in a living plant body.
• One group of PGRs is involved in growth-promoting activities, such as cell division, cell enlargement, pattern formation, tropic growth, flowering, fruiting, and seed formation
• The PGRs of the other group play an important role in plant responses to wounds and stresses of biotic and abiotic origin.
• A few examples of  PGRs are indole-3-acetic acid, abscisic acid, terpenes (gibberellic acid, GA3 ), or gases (ethylene, C2H4 ).

Explanation:

Option 1:

• IAA stands for indole acetic acid. It is a naturally occurring auxin.
• It is the derivative of indole. It is important in apical dominance, cell differentiation, elongation, tissue differentiation, etc.
• Apical dominance is a process of inhibition of the growth of lateral buds by the shoot tips that contain auxin hormone in it.

Option 2:

• Ethylene is a gaseous hormone that regulated both growth and senescence.
• It promotes fruit ripening, senescence, abscission of plant organs (mainly leaves), breaks seed dormancy, etc.

Option 3:

• Gibberellin is a plant growth regulator that has many physiological effects.
• Gibberellin plays a role in flowering, increases the length of the internode, delays senescence, and promotes rosette formation in cabbages.

Option 4:

• Cytokinin is another plant hormone that regulates plant growth and development.
• It promotes cell division, formation of leaves, formation of chloroplast, delays the process of senescence, etc.
• Cytokinin prevents apical dominance by encouraging lateral bud expansion during cell division.

So, the correct answer is option 4, Cytokinin.

Explanation:

Option 1:

• Auxin is another plant hormone responsible for apical dominance. Apical dominance is a process where the growth of lateral roots is inhibited due to the presence of auxin.  It also controls xylem differentiation. Indole acetic acid (IAA) is the naturally occurring auxin. Auxins such as 2,4-D act as a weedicide and can be used to form weed-free lawns.

Option 2:

• Cytokinin is another plant hormone that regulates plant growth and development. It promotes cell division, formation of leaves, formation of chloroplast, delays the process of senescence, etc.
• Zeatin is a hormone that belongs to the cytokinin family. It was discovered from corn Zea.
• Coconut water is rich in cytokinin.

Option 3:

• Gibberellin is a plant growth regulator that has many physiological effects.
• Gibberellin plays a role in flowering, increases the length of the internode, delays senescence, and promotes rosette formation in cabbages.
• As gibberellin helps in the elongation of internode length, they are sprayed on sugarcane to increase sugar production.
• The more the area, the more the sugar content of sugarcane.

Option 4:

• Ethylene is a gaseous hormone that regulates both growth and senescence.
• It promotes fruit ripening, senescence, abscission of plant organs (mainly leaves), breaks seed dormancy, etc.

So, the correct answer is Option 3, Gibberellin.