Mix Examples-Plant Growth and Development Questions in English

(A) The coiling of tendrils is a classic example of $Thigmotropism$.
$Thigmotropism$ is the directional growth movement of a plant in response to a touch stimulus or physical contact with a solid object.
When a tendril comes into contact with a support,the side in contact grows slower than the side away from the support,causing the tendril to coil around the object.

(A) The movement in the leaf lobes of $Dionaea$ (Venus flytrap) is a type of nastic movement known as $Thigmonasty$ (or $Thigmonastic$ movement).
This movement occurs in response to touch or mechanical stimulation.
When an insect touches the sensory hairs on the inner surface of the leaf lobes,the lobes close rapidly to trap the prey.
$Thigmonasty$ is a non-directional response to a touch stimulus.

(B) The leaves of $Mimosa$ $pudica$ (touch-me-not plant) exhibit seismonastic movement in response to physical contact or mechanical stimulation.
This movement occurs due to a sudden loss of turgor pressure in the cells of the $pulvinus$ (the swollen base of the leaf).
When the plant is touched,water moves out of the $pulvinus$ cells,causing the leaves to fold and droop.

(B) In plant tissue culture,growth regulators are essential for the differentiation and growth of explants.
Auxins and cytokinins are the primary plant hormones used as growth promoters.
Auxins (e.g.,$IAA$,$NAA$,$2,4-D$) promote root initiation and cell elongation.
Cytokinins (e.g.,$BAP$,$Kinetin$) promote shoot initiation and cell division.
Therefore,$(iv)$ Auxin and $(v)$ Cytokinin are the correct growth promoters used in culture media.

(B) $Cactushouse$ is a specialized greenhouse or botanical structure designed to provide optimal environmental conditions for the growth of $Xerophytes$.
$Xerophytes$ are plants adapted to survive in environments with little liquid water,such as deserts or ice- or snow-covered regions.
Since cacti are the most common examples of $Xerophytes$,these structures are specifically named $Cactushouses$ to facilitate their cultivation.

(B) The correct answer is $B$. Cytokinin and auxin are two essential plant hormones added to the tissue culture medium in specific proportions to regulate morphogenesis.
These hormones induce cell division and the differentiation of the callus.
Specifically,a low auxin-to-cytokinin ratio promotes the formation of shoots,while a high auxin-to-cytokinin ratio promotes the development of roots in the callus.

(C) : The growth movement in response to touch,or contact of a foreign body,in plants is called thigmotropism or thigmotropic movement.
The stems and tendrils of the climbers are positively thigmotropic in their response.
The coiling of garden pea tendrils around any support is an example of thigmotropism.
Thigmonastic (haptonastic) movements are induced by some external stimuli,but they are non-directional. For example,tentacles of $Drosera$ leaf curve and the lamina lobes of $Dionaea$ fold on coming in contact with an insect.

(A) : Gibberellic acid is a plant growth hormone that promotes cell elongation in stems and leaves,and internodal growth in dwarf plants.
It is a growth-promoting hormone and does not induce leaf abscission.
Leaf abscission (leaf fall) is primarily associated with Abscisic acid $(ABA)$,not Gibberellic acid.

(C) The development of fruits without fertilization is known as parthenocarpy,and such fruits are called parthenocarpic fruits.
Parthenocarpic fruits are typically seedless.
In horticultural practices,parthenocarpy can be artificially induced by applying plant growth regulators,specifically auxins and gibberellins,to the stigma or ovaries of the flowers.
These hormones mimic the signals usually provided by developing seeds,stimulating the ovary to grow into a fruit even in the absence of fertilization.
Therefore,treating the plants with low concentrations of gibberellic acid and auxins is a standard method to produce parthenocarpic tomato fruits.

(D) The incorrect pair is $ABA$ - flowering hormone.
$ABA$ (Abscisic Acid) is primarily known as a growth inhibitor and a stress hormone that promotes seed dormancy and stomatal closure.
Florigen is the hormone responsible for flowering,not $ABA$.
Auxin promotes growth (cell elongation).
Gibberellin was first discovered in the fungus $Gibberella$ $fujikuroi$.
Cytokinin was first isolated from herring sperm $DNA$ (as kinetin).

(D) Plant growth is influenced by both extrinsic (external) and intrinsic (internal) factors.
Extrinsic factors include environmental conditions such as light,temperature,water,oxygen $(O_2)$,carbon dioxide $(CO_2)$,and nutrients.
Intrinsic factors include genetic factors and plant growth regulators (hormones) such as auxins,gibberellins,cytokinins,etc.
Therefore,growth regulators and genetic factors are classified as intrinsic factors,not extrinsic factors.

(D) Plant growth regulators (PGRs) are classified based on their physiological effects on plant growth.
$1$. Plant growth promoters: These substances promote growth activities such as cell division,cell enlargement,pattern formation,tropic growth,flowering,fruiting,and seed formation. Examples include Auxins $(1)$,Gibberellins $(2)$,and Cytokinins $(4)$.
$2$. Plant growth inhibitors: These substances play a role in plant responses to wounds and stresses of biotic and abiotic origin. They are also involved in various growth-inhibiting activities such as dormancy and abscission. Abscisic acid $(3)$ is the primary plant growth inhibitor.
Therefore,$A$ (promoters) matches with $1, 2, 4$ and $B$ (inhibitor) matches with $3$.

(D) $1$. The increased growth per unit time is defined as the growth rate. It represents the rate of increase in size or biomass over a specific period.
$2$. Abscisic acid $(ABA)$ is a plant hormone known as a stress hormone. It plays a crucial role in closing the stomata during water stress to prevent excessive transpiration.

(D) The correct matching is as follows:
$A$. Cytokinin: Promotes lateral shoot growth $(iii)$.
$B$. Ethylene: Found in large amounts in tissues undergoing senescence $(iv)$.
$C$. Gibberellin: Increases stem length $(ii)$.
$D$. Abscisic acid: Stimulates closure of stomata $(i)$.
Therefore,the correct sequence is $A-iii, B-iv, C-ii, D-i$.

(A) The incorrect pair is $A$. Gibberellic acid $(GA_3)$ is primarily involved in stem elongation,seed germination,and breaking dormancy. It does not promote leaf fall (abscission). In fact,abscisic acid $(ABA)$ is the hormone primarily responsible for promoting abscission (leaf fall). Cytokinins are known to delay senescence by promoting nutrient mobilization. $IAA$ (Indole$-3-$acetic acid) is an auxin that prevents the abscission of young leaves and fruits. $ABA$ is a growth inhibitor that inhibits seed germination and promotes dormancy.

(A) $1$. Ethephon $(A)$ is an ethylene-releasing compound that hastens fruit ripening in tomatoes and apples $(S)$.
$2$. Abscisic acid $(ABA)$ $(B)$ is a growth inhibitor that inhibits seed germination $(P)$.
$3$. Gibberellic acid $(GA)$ $(C)$ is a growth promoter that helps overcome apical dominance $(R)$.
$4$. Therefore,the correct matching is $A-S, B-P, C-R$.

(D) An annual plant completes its life cycle (germination,growth,flowering,and seed production) within a single growing season and then dies. $A$ biennial plant completes its life cycle in two years; it grows vegetatively in the first year and produces flowers,fruits,and seeds in the second year before dying. Therefore,the fundamental difference is that an annual plant completes its life cycle and dies within one year,whereas a biennial plant does not die after the first year's growth.

(B) The movement of leaves in $Mimosa$ $pudica$ (touch-me-not plant) upon being touched is known as seismonasty.
Seismonasty is a type of nastic movement in plants that occurs in response to mechanical stimuli such as touch,vibration,or shaking.
This movement is caused by a sudden loss of turgor pressure in the cells of the pulvinus (the swollen base of the leaf stalk).
When the plant is touched,electrical and chemical signals cause water to move out of the pulvinus cells,leading to the drooping of the leaves.

(A) The correct answer is $A$ and $B$ are both incorrectly matched in the context of standard plant physiology,but typically in multiple-choice questions,we look for the most prominent error.
$1$. Gibberellic acid $(GA)$ promotes stem elongation and seed germination,while leaf abscission is primarily promoted by Abscisic acid $(ABA)$ and Ethylene. Thus,$A$ is incorrect.
$2$. Cytokinin promotes cell division (cytokinesis) and delays senescence,whereas cell wall elongation is primarily the function of Auxins $(IAA)$. Thus,$B$ is also incorrect.
$3$. $IAA$ (Indole$-3-$acetic acid) is an auxin that promotes cell wall elongation. This is correct.
$4$. Abscisic acid $(ABA)$ is known as the stress hormone that induces stomatal closure. This is correct.
Note: Since both $A$ and $B$ are incorrect,in many competitive exams,$A$ is often cited as the primary mismatch regarding abscission.

(A) Pineapple plants have a long vegetative growth phase before flowering.
To induce flowering artificially and ensure year-round production,specific plant growth regulators are used.
$Auxins$ (like $NAA$ or $2,4-D$) and $Ethylene$ are widely used in commercial pineapple cultivation to promote synchronous flowering.
$Ethylene$ is particularly effective in inducing flowering in pineapple,while $Auxins$ help in fruit development and uniform ripening.
Therefore,the combination of $Auxin$ and $Ethylene$ is the correct choice for increasing yield.

(D) Statement $I$ refers to Ethylene $(C_2H_4)$, which promotes root growth and root hair formation to increase the absorption surface.
Statement $II$ refers to Ethylene $(C_2H_4)$, which induces flowering in mango and promotes rapid internode/petiole elongation in deep-water rice plants to help them survive flooding.
Statement $III$ refers to Abscisic Acid $(ABA)$, which acts as a general plant growth inhibitor, inhibits seed germination, promotes seed dormancy, and helps plants withstand environmental stress.
Therefore, $X = C_2H_4$, $Y = C_2H_4$, and $Z = ABA$.

(N/A) The five main groups of natural plant growth regulators are:
$(i)$ Auxins
$(ii)$ Gibberellins
$(iii)$ Cytokinins
$(iv)$ Ethylene
$(v)$ Abscisic acid
Note on Auxins:
Discovery: Charles Darwin and Francis Darwin observed that canary grass coleoptiles bent toward light. Later,$F$.$W$. Went isolated auxins from the tips of oat seedlings.
Physiological functions: They promote cell elongation,apical dominance,and vascular tissue differentiation. They also induce parthenocarpy.
Agricultural/Horticultural applications: Used as rooting hormones in stem cuttings,as weedicides (e.g.,$2,4-D$),and to induce fruit set in tomatoes.

(N/A) Induce rooting in a twig: Auxins (e.g.,$IBA$,$NAA$ are used for rooting in stem cuttings).
$(b)$ Quickly ripen a fruit: Ethylene (it is a gaseous hormone that promotes fruit ripening).
$(c)$ Delay leaf senescence: Cytokinins (they promote cell division and delay the aging process in leaves).
$(d)$ Induce growth in axillary buds: Cytokinins (they help overcome apical dominance and promote lateral bud growth).
$(e)$ 'Bolt' a rosette plant: Gibberellic acid (it induces internode elongation just prior to flowering in rosette plants like cabbage).
$(f)$ Induce immediate stomatal closure in leaves: Abscisic acid (it acts as a stress hormone and triggers stomatal closure during water stress).

(N/A) If $GA_{3}$ is applied to rice seedlings,the seedlings will exhibit internode elongation and an increase in height.
$(b)$ If dividing cells stop differentiating,plant organs such as leaves and stems will not be formed. The mass of undifferentiated cells is called a callus.
$(c)$ If a rotten fruit is mixed with unripe fruits,the ethylene produced by the rotten fruit will hasten the ripening of the unripe fruits.
$(d)$ If you forget to add cytokinin to the culture medium,cell division,growth,and differentiation will not be observed.

(D) Different types of questions arise in our mind when we think about plants.
$1$. Where and how do structures like roots,stems,leaves,flowers,fruits,and seeds arise,and that too in an orderly sequence?
$2$. We are aware of the terms seed,seedling,plantlet,and mature plant. We have also seen that trees continue to increase in height or girth over a period of time.
$3$. The leaves,flowers,and fruits of the same tree not only have limited dimensions but also appear and fall periodically and sometimes repeatedly.
$4$. Why does the vegetative phase precede flowering in a plant?
$5$. All plant organs are made up of a variety of tissues. Is there any relationship between the structure of a cell,a tissue,an organ,and the function they perform?
$6$. Can the structure and the function of these be altered?
$7$. All cells of a plant are descendants of the zygote. The question is,then,why and how do they have different structural and functional attributes?
Since all these questions are relevant to the study of plant growth and development,the correct answer is $D$.

(N/A) $(1)$ Gibberellins: These are acidic plant growth regulators that promote stem elongation,seed germination,and flowering. They are responsible for breaking seed dormancy and are widely used in the brewing industry to speed up the malting process.
$(2)$ Cytokinins: These are plant hormones that promote cell division (cytokinesis). They are primarily synthesized in regions where rapid cell division occurs,such as root apices and developing shoot buds. They help in producing new leaves,lateral shoot growth,and adventitious shoot formation. They also help delay leaf senescence.

(N/A) Plant hormones,also known as phytohormones,are chemical substances produced naturally in plants that regulate growth,development,and physiological responses. Their general effects include:
$1$. Growth Promotion: Auxins,gibberellins,and cytokinins promote cell division,cell elongation,and tissue differentiation.
$2$. Growth Inhibition: Abscisic acid $(ABA)$ acts as a growth inhibitor,promoting dormancy in seeds and buds,and inducing stomatal closure during water stress.
$3$. Developmental Regulation: Hormones control processes like flowering,fruit ripening (e.g.,ethylene),and senescence (aging).
$4$. Stress Response: They help plants adapt to environmental stresses such as drought,salinity,and temperature fluctuations.

(N/A) $(1)$ Cell enlargement vs Cell differentiation:

Cell Enlargement	Cell Differentiation
$(1)$ It involves the increase in size of cells formed after division.	$(1)$ Cells undergo structural changes to perform specific functions.
$(2)$ The size of the vacuole increases.	$(2)$ Specialized tissues are formed.
$(3)$ Cell wall growth is responsible for cell enlargement.	$(3)$ Cells differentiate to form complex tissues.
$(4)$ The size of the cell increases.	$(4)$ The size and shape of the cells become permanent.

$(2)$ Epigeal germination vs Hypogeal germination:

Epigeal Germination	Hypogeal Germination
$(1)$ Cotyledons are pushed above the soil surface.	$(1)$ Cotyledons remain below the soil surface.
$(2)$ Hypocotyl elongates significantly.	$(2)$ Epicotyl elongates significantly.
$(3)$ Example: Bean (Phaseolus vulgaris).	$(3)$ Example: Maize (Zea mays).
$(4)$ It is typical of dicots.	$(4)$ It is typical of monocots.

(N/A) $(1)$ Auxins $(IAA)$ vs. Abscisic acid $(ABA)$:
- Auxins are growth-promoting hormones that stimulate cell elongation,root initiation,and apical dominance.
- Abscisic acid $(ABA)$ is a growth-inhibiting hormone that promotes seed dormancy,stomatal closure during water stress,and abscission of leaves and fruits.
$(2)$ Gibberellins vs. Ethylene:
- Gibberellins are growth-promoting hormones that stimulate stem elongation,seed germination,and flowering.
- Ethylene is a gaseous hormone that primarily promotes fruit ripening,senescence of leaves and flowers,and horizontal growth of seedlings.

(D) The differences between plant and animal hormones are as follows:
$1$. Origin: Plant hormones are synthesized in various tissues (meristematic,developing seeds,etc.),whereas animal hormones are produced in specific endocrine glands.
$2$. Chemical Nature: Plant hormones are often simple molecules (e.g.,$Auxins$,$Gibberellins$),while animal hormones are complex molecules like proteins,peptides,or steroids.
$3$. Transport: Plant hormones move through the xylem or phloem or via diffusion,while animal hormones are transported through the blood circulatory system to target organs.

(N/A) $(1)$ Plant hormone (Phytohormone): These are chemical substances produced naturally in plants that act in very low concentrations to regulate growth,development,and physiological processes. Examples include Auxins,Gibberellins,Cytokinins,Abscisic acid,and Ethylene.
$(2)$ Deciduous: This term refers to plants (typically trees or shrubs) that shed their leaves annually,usually during a specific season such as autumn or during periods of drought,to conserve water and energy.

(N/A) Positive role of ethylene: Influences of ethylene on plants include horizontal growth of seedlings,swelling of the axis,and apical hook formation in dicot seedlings. Ethylene breaks seed and bud dormancy,initiates germination in peanut seeds,and promotes the sprouting of potato tubers.
Negative roles of ethylene: Ethylene promotes senescence and abscission of plant organs,especially of leaves and flowers.
Positive role of abscisic acid: $ABA$ plays an important role in seed development and maturation.
Negative roles of abscisic acid: It acts as a general plant growth inhibitor and an inhibitor of plant metabolism. $ABA$ inhibits seed germination. $ABA$ stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses.

(D) It is difficult to attribute an observed effect to a single hormone because of the following reasons:
$1$. Phytohormones are synthesized by plant cells individually, but they often exhibit overlapping functions. For example, both $Auxins$ and $Gibberellins$ $(GA)$ can promote stem elongation.
$2$. There is no separate, dedicated system for the translocation of each hormone; they often move through the same pathways, leading to intermixed effects.
$3$. Phytohormones often act synergistically or antagonistically. For instance, $Ethylene$ and $Abscisic$ $Acid$ $(ABA)$ support each other in various physiological roles.
$4$. The effects of phytohormones observed $in$ $vitro$ (in a laboratory setting) often differ significantly from those observed $in$ $vivo$ (within the living organism) due to the complex interaction of multiple signaling pathways.

(B) The process of $parthenocarpy$ produces seedless fruits.
This is a biological process in which fruits develop without the process of fertilization, resulting in the absence of seeds within the fruit.
Artificially, $parthenocarpy$ can be induced by spraying plant growth regulators, specifically $auxins$ and $gibberellins$, on the flowers to produce seedless watermelons.

(A) $(1)$ The maximum growth rate is observed during the exponential phase (log phase),where the growth is rapid and follows a geometric progression.
$(2)$ Apical dominance is caused by the hormone auxin,which is produced in the apical buds and inhibits the growth of lateral buds.

(A-ETHYLENE, B-AUXIN, C-ETHYLENE, D-2,4-D, E-GIBBERELLINS) Ethylene is a plant hormone that exists in a gaseous state at room temperature.
$(B)$ Auxin is primarily responsible for phototropism,as it promotes cell elongation on the shaded side of the stem.
$(C)$ Ethylene promotes the development of female flowers in cucumber plants,thereby increasing the yield.
$(D)$ Synthetic auxins,such as $2,4-D$ ($2,4-dichlorophenoxyacetic$ acid),are used as herbicides to selectively kill broad-leaved dicot weeds.
$(E)$ Gibberellins are known to induce flowering in many long-day plants,especially under non-inductive conditions.

(A) $(1)$ During the initial phase of growth,the rate is slow,which is called the Lag phase. During the rapid growth phase,the rate of growth increases exponentially,which is called the Log phase or Exponential phase.
$(2)$ $IAA$ (Indole$-3-$acetic acid) is a type of auxin,which is an indole compound. Abscisic acid $(ABA)$ is a plant growth inhibitor derived from carotenoids.

(A) $(1)$ $Skoog$ and $Miller$ discovered the effects of $Cytokinin$ (kinetin),while $Cousins$ confirmed the release of a volatile substance from ripened oranges that hastened the ripening of stored unripened bananas,which was later identified as $Ethylene$.
$(2)$ $Cytokinin$ was discovered from autoclaved $Herring$ fish $DNA$. Similarly,$Gibberellin$ was discovered from the fungus $Gibberella$ $fujikuroi$ (which causes 'bakanae' or 'foolish seedling' disease in rice).

(A) partial parasite is a plant that derives some of its nutrients from a host but can perform photosynthesis. $Viscum$ (also known as $Loranthus$ or mistletoe) is a partial parasite because it has chlorophyll and can photosynthesize,but it derives water and minerals from the host plant.
$A$ total parasite is a plant that is completely dependent on the host for all its nutrients and water,lacking chlorophyll. $Cuscuta$ (dodder) is a classic example of a total parasite as it lacks chlorophyll and derives all its nutrition from the host plant.
Therefore,the correct sequence is $Viscum$ (partial parasite) and $Cuscuta$ (total parasite).

(A) The correct matches are as follows:
$(a)$ Fruit ripener: Ethephon $(iv)$. Ethylene is a gaseous hormone that promotes fruit ripening.
$(b)$ Herbicide: $2,4-D$ $(ii)$. $2,4-D$ is a synthetic auxin used as a weedicide.
$(c)$ Bolting agent: $GA_{3}$ $(iii)$. Gibberellins promote internode elongation just prior to flowering, a process known as bolting.
$(d)$ Stress hormone: Abscisic acid $(i)$. $ABA$ is known as the stress hormone as it helps plants withstand various environmental stresses.
Therefore, the correct sequence is $(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)$.

(B) Plant growth regulators (PGRs) are organic compounds that influence the growth and development of plants.
$IAA$ (Indole$-3-$acetic acid) and $2IP$ ($2$-isopentenyl adenine) are natural plant hormones.
$GA_{3}$ (Gibberellic acid),$ABA$ (Abscisic acid),and $IBA$ (Indole$-3-$butyric acid) are also recognized as plant growth regulators.
Zinc $(Zn)$ is an essential micronutrient required for plant metabolism and enzyme activation,but it is not classified as a plant growth regulator or hormone.
Therefore,the set containing $Zn$ is not a set of plant growth regulators.

(A) Plant growth regulators are broadly classified into two groups: plant growth promoters and plant growth inhibitors.
Plant growth promoters include auxins (e.g.,$NAA, IBA, IAA$),gibberellins (e.g.,$GA_3$),and cytokinins (e.g.,Zeatin,$BAP$).
Plant growth inhibitors include substances like Abscisic acid $(ABA)$.
In option $A$,$NAA$ (auxin),$IBA$ (auxin),Zeatin (cytokinin),and $GA_3$ (gibberellin) are all growth promoters.
Options $B, C,$ and $D$ contain $ABA$,which is a growth inhibitor.

(D) Colchicine is an alkaloid that inhibits the formation of spindle fibers during cell division (mitosis) by binding to tubulin proteins.
As a result,the sister chromatids fail to separate,leading to a state of polyploidy where the chromosome number is doubled in the daughter cells.

(B) Water stress leads to a reduction in the turgor pressure of plant cells,which causes the leaves to $A-wilt$.
As the leaves wilt,they curl or droop,which effectively $B-decreases$ the surface area available for photosynthesis.
Additionally,water stress limits the availability of water for metabolic processes,thereby reducing the overall metabolic activity of the plant.

(A) $I.$ Cytokinin is known to delay leaf senescence by promoting nutrient mobilization.
$II.$ Auxin is responsible for apical dominance,where the apical bud inhibits the growth of lateral buds.
$III.$ Ethylene is primarily associated with fruit ripening and horizontal growth of seedlings,not seed germination (which is primarily promoted by Gibberellins).
$IV.$ Gibberellins promote growth and seed germination; the immature falling of leaves (abscission) is primarily promoted by Abscisic Acid $(ABA)$ and Ethylene.
Therefore,statements $I$ and $II$ are correct.

(B) Abscisic acid $(ABA)$ is known to promote stomatal closure during water stress.
Cytokinins are primarily responsible for promoting cell division in plants.
$IAA$ (Indole$-3-$acetic acid),an auxin,promotes cell wall elongation and cell enlargement.
Gibberellic acid $(GA)$ promotes stem elongation,seed germination,and flowering,but it does not promote leaf fall. Leaf fall (abscission) is primarily promoted by Abscisic acid $(ABA)$ and ethylene. Therefore,the pair 'Gibberellic acid - Leaf fall' is incorrectly matched.

(C) The movement which occurs due to the difference in the rate of growth on two opposite sides of a plant organ is called nastic movement.
When movement occurs due to faster growth of the upper surface of an organ compared to the lower surface,it is called epinasty.
The opening of a flower is a classic example of epinastic movement,where the growth of the inner surface of the petals is faster than the outer surface,causing the flower to open.