Answer

(b) Ethylene is a gaseous hormone and is produced by the ripened fruits and also help in ripening of other unripened fruits. Other mentioned functions are not of ethylene.

• (a) Ethylene does not retard the ripening of tomatoes; it actually promotes ripening.
• (c) Ethylene does not slow down the ripening of apples; it accelerates the ripening process.
• (d) Ethylene cannot both hasten and slow down the ripening of fruits; it only hastens the ripening process.

Thinking Process

Coconut is a drupe fruit. It has edible endospermic layer.

Answer

(c) Coconut milk is the liquid endosperm in unripened fruit and is rich in plant hormone cytokinin. The other hormones are absent in coconut milk.

• ABA (Abscisic Acid): Coconut water does not contain significant levels of ABA. ABA is primarily involved in stress responses and seed dormancy, and it is not a major component of coconut water.

• Auxin: While auxins are important plant hormones involved in growth and development, they are not present in significant amounts in coconut water. Auxins are more commonly found in other parts of the plant, such as the tips of roots and shoots.

• Gibberellin: Gibberellins are another class of plant hormones that promote growth and influence various developmental processes. However, they are not a major component of coconut water. Gibberellins are typically found in higher concentrations in other parts of the plant, such as seeds and young leaves.

Thinking Process

Various plant growth hormones are involved in the growth and development of the plant.

Answer

(d) Cytokinin is antagonistic to the action of auxin and thus overcome the phenomenon of apical dominance.

Whereas, IAA, helps in apical dominance, ethylene in ripening of fruits and gibberellin in overcoming bud and seed dormancy.

• IAA helps in apical dominance, thus it does not overcome it.
• Ethylene is involved in the ripening of fruits, not in overcoming apical dominance.
• Gibberellin helps in overcoming bud and seed dormancy, not in overcoming apical dominance.

Answer

(a)

A. IAA-Weed free lawn 2-4 D and synthetic indole acetic acid kill the broad leaf weeds Thus, used as weedicides.

B. ABA-Stomatal closure ABA is a stress hormone. Under water stressed conditions, it shuts down stomata to reduce the rate of transpiration.

C. Ethylene, a gaseous hormone is responsible for ripening of fruits.

D. GA Gibberellic acid does the phenomenon of bolting, i.e., when sprayed on the plant, it increases the internodal region of stem, thus making a plant extremely tall.

E. Cytokinin was isolated from herring sperm DNA, for the first time. Other option are incorrect.

• Option (b) is incorrect because:

  • IAA is not responsible for the ripening of fruits; it is used as a weedicide.
  • Ethylene is responsible for the ripening of fruits, not for weed-free lawns.

• Option (c) is incorrect because:

  • ABA is not associated with herring sperm DNA; it is responsible for stomatal closure.
  • Ethylene is responsible for the ripening of fruits, not for weed-free lawns.
  • GA is responsible for bolting, not for stomatal closure.

• Option (d) is incorrect because:

  • IAA is not responsible for the ripening of fruits; it is used as a weedicide.
  • Ethylene is responsible for the ripening of fruits, not for bolting.
  • GA is responsible for bolting, not for herring sperm DNA.

Thinking Process

Growth and development of a plant is a complex process involving different plant hormones.

Answer

(b) Synergistic effect means when two hormones work together, they increase the effect or functioning of each other so, there will be enhanced effect of both the hormones.

Other options (a), (c) and (d) are stating is correct statements.

• Option (a) is incorrect because it describes antagonistic action, where two hormones act together but bring about opposite effects.
• Option (c) is incorrect because it describes pleiotropic action, where one hormone affects more than one function.
• Option (d) is incorrect because it describes a situation where many hormones bring about a single function, which is not specific to synergistic action.

Answer

(b) Apples have lenticels on their skin so, they respire. They are wrapped in wax paper after harvesting so as to prevent the respiration and over ripening of the apples.

Other option do not support the reason for wrapping apple into waxed paper.

• (a) Preventing sunlight from changing its color: Apples are not typically wrapped in waxed paper to prevent color change due to sunlight. The primary purpose of waxed paper is not to block sunlight but to control respiration and moisture loss.

• (c) Prevent ethylene formation due to injury: While ethylene is a ripening hormone, waxed paper does not specifically prevent its formation due to injury. The main function of waxed paper is to reduce respiration and moisture loss, not to inhibit ethylene production.

• (d) Make the apples look attractive: Although waxed paper might make apples look more presentable, the primary reason for wrapping apples in waxed paper is to control respiration and prevent over-ripening, not merely for aesthetic purposes.

Answer

(d) All the said statements are true for growth in a living organism.

• There are no incorrect options in this question. All the given parameters (increase in cell number, increase in cell size, and increase in length and weight) are valid measures of growth in a living organism.

Thinking Process

Plants have tremendous ability to adapt to the environment for their survival.

Answer

(b) The plants have the ability to change its phenotype according to the changes in environment. So, the plant growth show plasticity (ability to change/adapt according to environment).

• (a) Plant roots being extensible refers to the ability of roots to grow and extend, but this does not encompass the broader concept of plasticity, which involves the plant’s ability to change its overall growth and development in response to environmental conditions.

• (c) Stems being able to extend refers to the elongation of stems, which is a specific growth process. However, plasticity in plant growth involves a wider range of adaptive changes in response to the environment, not just stem elongation.

• (d) “None of the above” is incorrect because option (b) correctly describes plasticity in plant growth as the ability to change and adapt according to environmental conditions.

Answer

(c) Gibberellin spray on sugarcane induces the growth in the internodal area of the sugarcane plant. Larger is the area larger will the sugar content, as sucrose is the main constituent in the of sap of sugarcane stem.

• IAA (Indole-3-acetic acid): IAA is a type of auxin, which primarily promotes cell elongation and root formation. It is not specifically known for increasing sugar production in sugarcane.

• Cytokinin: Cytokinins are involved in cell division and growth, as well as delaying leaf senescence. They do not specifically enhance sugar production in sugarcane.

• Ethylene: Ethylene is a plant hormone that regulates fruit ripening and leaf abscission. It does not play a direct role in increasing sugar content in sugarcane.

Thinking Process

Sometimes some phytohormones act opposite to each other but this act could be beneficial for the plant.

Answer

(c) Gibberellic acid ABA is stress hormone as it induces seed dormancy in plants. Whereas, gibberellic acid breaks down seed dormancy and induces seed germination so, both act opposite to each other, the refer are antagonistic to each other.

• Ethylene: Ethylene is primarily involved in processes like fruit ripening, leaf abscission, and flower wilting. It does not have a direct antagonistic relationship with ABA in terms of seed dormancy and germination.

• Cytokinin: Cytokinins are involved in cell division, shoot initiation, and delay of leaf senescence. They do not directly oppose ABA’s role in seed dormancy and germination.

• IAA (Indole-3-acetic acid): IAA is a type of auxin that promotes cell elongation, root formation, and differentiation. It does not have a direct antagonistic relationship with ABA in the context of seed dormancy and germination.

Answer

(b) Monocarpic plants flower once and die. The plants like Bamboo flower only once during their life cycle. Thus, these plants are called monocarpic plants.

• Option (a) is incorrect because monocarpic plants are not defined by the number of ovaries in their flowers. The term “monocarpic” specifically refers to plants that flower once and then die, regardless of the number of ovaries in their flowers.

• Option (c) is incorrect because monocarpic plants are not defined by bearing only one flower. Monocarpic plants can produce multiple flowers during their single flowering event before they die.

• Option (d) is incorrect because not all the given statements (a, b, and c) are true for monocarpic plants. Only statement (b) correctly defines monocarpic plants.

Thinking Process

A typical photoperiod exposer is the requirement of the plants for flowering however, for some plant it is not necessary.

Answer

(d) Fully developed leaves receive the stimulus of light photoperiodism is the effect of light and its duration on the growth and development especially flowering in plants.

Even a single leaf as its part is part is capable of inducing photoperidism but very young leaves are insensitive to light. Other parts meristem flower and floral buds denot perceive the stimulus.

• Meristem: The meristem is a region of plant tissue, found chiefly at the growing tips of roots and shoots, consisting of actively dividing cells forming new tissue. It does not perceive the stimulus of light for photoperiodism.
• Flower: The flower is the reproductive structure of the plant and does not have the capability to perceive light stimuli for photoperiodism.
• Floral buds: Floral buds are the early stages of flower development and do not have the ability to perceive light stimuli for photoperiodism.

Answer

(a) A phase of growth which is maximum and fastest is exponential phase.

(b) Apical dominance as expressed in dicotyledonous plants is due to the presence of more auxins in the apical bud than in the lateral ones.

(c) In addition to auxin, a cytokinin must be supplied to culture medium to obtain a good callus in plant tissue culture.

(d) Leaves of vegetative plants are the sites of photoperiodic perception.

Thinking Process

Pytohormones have their effect on various developmental and physiological functions of the plants.

Answer

(a) Gibberellic acid increases the yield of sugarcane.

(b) Cytokinin spray on plants promote lateral shoot growth.

(c) The effect of ethylene on potato causes its sprouting.

(d) ABA - Abscissic acid inhibit the seed germination.

Answer

Growth is dependent on three factors - initial size $\left(W_{0}\right)$, rate of growth $(r)$ and time interval $(+)$ for which the rate of growth is retained.

Where,

$$ \begin{aligned} & W_{1} =W_{0} e^{r t} \\ \text{where, }\quad \quad \quad \quad & W_{1} =\text { final size, } \\ & W_{0} =\text { Initial size, } \\ & r =\text { growth rate, } \\ & t =\text { time, } \\ & e =\text { base of natural logarithim. } \\ & 19 =5 \times(2.7)^{r \times 7} \\ & \frac{19}{5} =(2.7)^{r \times 7} \\ & 3.8 =(2.7)^{r \times 7} \end{aligned} $$

$$ \begin{aligned} \log 3.8 & =r \times 7 \times \log (2.7) \\ 0.5798 & =r \times 7 \times 0.4314 \\ \frac{0.5798}{7 \times 0.4314} & =r=0.1907 \\ \text { Relative growth rate } & =\frac{\text { Growth in given time period }}{\text { Measurement at start of time period }} \\ & =\frac{19}{5}=3.8 \mathrm{~cm} \end{aligned} $$

Thus absotule growth rate is 0.1907 while relative growth rate is $3.8 \mathrm{~cm}$.

Answer

(a) The hormone, gibberellin

(i) Produce the phenomenon of bolting, i.e., the growth of the internodal region of stem in rosette plants.

(ii) Induces seed germination and break bud and seed dormancy.

(b) The rice seedling/plant show excessive growth in their internodal region when get infected with fungus Gibberella fujikuroi. This fungus produces excessive amount of plant hormone GA which makes plants taller than the normal plant foolishly and many result into death of the plant.

Answer

Besides some primary function, both gibberellins and ethylene have some special effect on some specific plants as

Gibberellin promotes the formation of male flower an genetically female plants while ethylene promotes formation as Female flowers an genetically, male plants.

Answer

Long Day Plant (LDP) Some plants require the exposure light for a longer period exceeding a well defined critical duration of light. Among the above given plant LDP are for flowering henbane, Bryophyllum and spinach.

Short Day Plants (SDP) Some plants flower when and these can blossom throughout the year. expos to light for a period less than well defined critical duration of light. e.g., of SDP are. e.g., Xanthium, rice, strawberry.

Day Neutral Plants (DNP) The exposure to light does not affect the flowering in certain plants, e.g., DNP, are sunflower, tomato, maize.

Thinking Process

Ethylene is a gaseous plant hormone. It is primarily responsible for ripening of fruits.

Answer

Ethylene is also responsible to play a major roll in determining the sex of monoecious flowers and is associated with the promotions of femaleness in plants thus the farmer must spray ethylene hormone on this cucumber crop to produce female flowers and to increase the yield (number of fruits produced).

Answer

(a) IAA Indole acetic acid is the chemical name of auxin. It is synthesised at the growing apices of the plant, e.g., shoot tip, leaf primordia and developing seeds.

(b) Gibberellins It plays an important role in seed germination of plants and is synthesised in the apical shoot buds, young leaves, root tips and developing seeds.

(c) Cytokinins This plays an important role in actively dividing cells and are synthesised mainly in roots, but syntheses also occurs in endosperm of seeds growing embryo and seeds etc.

Answer

The apical buds present in tea and other plants prevents the growth of lateral buds in them, by releasing auxin hormone. This phenomenon is called apical dominance, Trimming of tea garden and botanical garden removes the apical bud and allowing the lateral buds to grow laterally and give plants a dense bushy appearance.

The scientific explanation for this trimming method is that apical bud is removed thus results in the removal of auxin and phenomenon an of apical dominance is overcomed.

Answer

(i) Photosynthesis It is a totally light dependent process. Both quality and quantity affect the rate of the process resulting into total biomass accumulation by plants.

(ii) Transpiration It is loss of water by plant surface. Presence of light increases the temperature, thus affecting the rate of transpiration in plants.

(iii) Flowering The duration of light on plants effects the growth and development of plants, e.g., particularly flowering and this phenomenon is known as photo periodism. On the basis of photoperiodic response day flowering plants are categorised as long day, shert day and day neutral plants.

Answer

1 Lag phase-Growth is slow in this phase.

2 Exponential phase-shows rapid growth and maintains maximum growth for sometime.

3 Stationany phase-Growth diminishes and ultimately stops in this phase.

Answer

Growth is the main character which distinguish living organisms from non-living. All living organism grow in number and then accumulate biomass and grow in size as well.

The growth is exhibited by all living organisms in terms of increase in number of cells as well as increase in size and length of each cell.

In unicelluar organism, show growth and the growth is synchronous with reproduction. Unicellular organism when divide they produce offsprings (reproduction) i.e., each cell accumulate (synthesise) protoplasm and increase in size but up to a limit and divide to from two cells.

Answer

The fungus Gibberella fuijkuroi when infects rice plant, it causes increase in internodal area of rice so, that the rice plant become foolishly tall as compored to normal ones. This is because this fungi produces GA in considerably higher amounts which causes over growth of rice plants thus, causing foolish disease.

Answer

Short day plants are those plants that flower only when the photoperiod (exposure to duration of light) is below critical period. Tobacco, being a short day plant is unable to show flowering when exposed to light above than the critical period.

Answer

(a) Meristematic cells near root tip The cells of this region are called Root Apical Meristems (RAM) and are in active state of division, thus their number increases continuously. The cells of this region are thin walled with dense cytoplasm and large nucleus. They have the ability to divide and self perpetuate.

(b) The Cells in the Elongation Zone of the Root This region is situated just above the meristematic zone. In the cells of this zone, a large number of small vacuoles develop and later these vacuoles fuse to form one large central vacuole filled with cell sap. The cells are elongated in this region.

Answer

Growth in plants is of indeterminate type, i.e., plant grow through out their life because of presence of meristematic tissues present in specific parts of plant i.e., apical intercalary and lateral. These tissue has ability to divide continuously and contribute to localised plant growth.

Growth in animals They have limited growth period after which further growth of their body stops.

All the parts of the plant do not grow indefinitely. The root apex and shoot apex having apical meristematic tissues keep growing, thus contributing to the elongation of plant axis-(height).

Answer

(a) Differentiation is permanent in size, structure, composition and function of cells, tissue or organs For example the meristematic tissues in plants gives rise to new cells which mature and get differentiated into special tissue or an organ of the plant, e.g., cells, distal to root apical meristem form root cap, cell of the periphery form epiblema, followed by cortex, endodermis, pericycle and vascular.

(b) De-differentiation is the process of despecialisation of differentiated cells so that they again become differentiated and able to divide. e. $g$., in dicot stem, the cortical cells get de-differentiated and become meristematic to form cambium (interfascicular cambium, and fascicular cambiums).

(c) Re-differentiation The cambium cells thus formed, again re-differentiate to form secondary cortex cells secondary xylem and phloem elements and phelloderm in case of secondary growth of woody dicot plants.

Answer

Auxin is an important plant phytohormone required for the growth and development of every plant in its life cycle.

(a) Auxin Precursors are raw materials required to initials synthesis of auxins. IAA is synthesised from tryptophan, adenine compounds and derivatives of carotenoids.

(b) Anti-Auxins are compounds that inhibit action of auxins, e.g., p-chlorophenoxy isobutyric acid (PCIB), TIBA.

(c) Synthetic Auxin These are synthesised not by plants but artificially by man, e.g., 2-4 D (weedicide), NAA, dicamba and IBA, (Indole Butyric Acid) which are natural as well as synthetic auxin.

Answer

Answer

Phytohormones are synthesised by plant cells, itself and individually. These are auxin, GA, ABA ethylene and cytokinin. There is not a separate system of their translocation in plants. So, their effects on plants are also inter mixed. e.g., many effects of auxins GA shows the same function. Similarly, ethylene and ABA support each other for many roles in plants.

Secondly, effects of phytohormone in vitro and in vivo will also be different.

Answer

The phenomenon by which apical bud suppress the growth of lateral buds is known as apical dominance. It is caused due to release of plant hormone auxin from apical duds.

It can be overcome either by the spray of cytokinin, that promotes the growth of lateral buds or by trimming of bushes which remove apical buds and allow lateral buds to grow.

Answer

The plant hormones are synthesised by the plant cells individually accordingly and when needed. Few hormones are specifically synthesised at a particular plant part, like auxin synthesised in growing shoot apices.

Ethylene is emitted by ripened fruits. Cytokinin is found in dividing cells. Unlike plants animal being more advanced, and organised they have proper hormone secreting glands and organs.

In both plant and animals these are transported through the transport system of their body. In plants, hormones are translocated via xylem and phloem to the site of activity.

Answer

Discovery of plant hormone gibberellins was made by chance. It happened by chance in rice fields. A few plants of rice were observed, which were unusually taller than the normal ones. Scientific investigation revealed, that these were infected with a fungus, known as Gibberella fufikuroi.

This fungus releases a plant hormone gibberellic acid in excess concentrations which made the plant to grow unusually tall. This compound was later known as gibberellin is hormones present in all plants.

The term used for accidental finding is Serendipity which means fortunate happenstance. It was coined by Horace Walpole in 1754. He explained it as making discoveries, by accident and sagacity, of things, which were hot in quest of.

Thinking Process

Apical dominance is overcome when apex of the growing plant is removed. It causes lateral branches of the plant to grow faster giving the plants a bushy appearance.

Answer

Regular mowing (cutting at apex) of lawn grass removes the apical portion of the plant which causes the lateral branches to grow faster. As the apical buds inhibits growth of lateral buds by releasing auxin, the phenomenon called apical dominance.

Because of mowing of the grass, it becomes bushy and growth is faster. So, as to make evenness of the grass (carpet-like) in the lawn this practice is followed regularly to overcome the problem of apical dominance.

Answer

The meristematic cells can be identified of the basis of the following characteristics

(i) Cell have thin cellulose wall and dense cytoplasm with large nucleus.

(ii) Plasmodesmal connections are more numerous among meristematic cells.

(iii) Cell division, i.e., mitosis and its various stages are distinctly visible.

(iv) Chromosomes of cells replicate and divide into two homologous chromatids.

All these features contribute to open ended growth where structure is never complete in meristematic regions.

Whereas, cells incapable of divinding show features such as

(i) attains particular shape, size and thickening

(ii) Undergoes structural and physiological differentiation.

(iii) Different types of cell are formed such as epidermis, cortex, vascular tissues.

Answer

Answer

Representation the labelling of the given diagram is as follows

A. The plant part in the given diagram is growing shoot apex.

B. Removal of shoot apex will help to overcome the apical dominance. Thus, the lateral buds grow faster, giving rise to branches and give the plant a bushy appearance.

Answer

Growth and differentiation in plant and animals can be explained as follows

Sponges are exception to this. They show open growth as every cell of their body can give rise to an individual and their growth and differentiation is continuous is their life cycle.

Thinking Process

Seedless fruits are developed in some plants. Certain phytohormone induce development of fruit without fertilisation.

Answer

Parthenocarpy is the process where fruit develop without fertilisation and so, it does not contain seed. This can also be induced artificially by spraying auxin and gibberellins in certain plants like, grapes, papaya, etc.

Answer

The process of parthenocarpy produce the seedless fruits. This is a process in which fruits are developed without fertilisation, so, seeds are not formed in the fruit. Artificially parthenocarpy can be induced by spraying auxin and gibberellin to produce seedless watermelans

Answer

The broad leaved dicot weeds can be killed and eliminated by the spray of weedicide 2-4 D, (a kind of plant phytohormone auxin). This will make the lawn free of weeds and will help the gardener, to make the lawn weed free.

Answer

A. As soon as seed germinates, the plant enters into vegetative growth period. This period takes light stimulus (a critical length of light exposed to different plant, i.e., photoperiod) and synthesise the florigen (a flowering hormone) which induce flowering.

B. The vegetative growth period prepares the plant to bear reproductive structures like flower, fruits and seeds, and allows it to grow, mature and reproduce.

Answer

A. Exponential

B. Auxin

C. Cytokinin

D. Phytochrome.

Thinking Process

The chilling treatment to wheat seed prior to sowing reduces the vegetative growth period of wheat plant and induces flowering at an early time.

Answer

Some annual food plants such as wheat do not flower, unless they experience a low temperature. They remain vegetative during spring (warm period) but grow further to bear flowers and fruits after receiving low temperature (in winter).

The low temperature in winter prevents precocious reproductive development in autumn, thus enabling the plant to reach vegetative maturity before reproductive phase.

Thus, when spring varieties are planted in spring, they flower and bear fruits prion to end of growing season. But, if the winter varieties are planted in spring, they fail to flower and produce mature grains before the end of growing season, as they could not perceive low temperature of winters.

Answer

A. Annual winter wheat plants take one year full growing season for the completion of their vegetative growth period and then initiate flowers and fruits. This is because after they form seedlings in autumn, they receive low temperature throughout winter, which enables them to reach vegetative maturity. They resume growth in spring and bear flowers and grains towards mid-summer.

B. The chilling or cold treatment of seeds to reduce flowering is called vernalisation. It is a process of shortening of the juvenile or vegetative phase and hastening flowering by a previous cold treatment. This stimulus of vernalisation is perceived only by the meristematic cells. e.g., shoot tip, embryo tip, root apex, developing leaves, etc.

C. GA or gibberellic acid treatment can replace cold treatment and can induce flowering early by reducing vegetative growth period in many long-day plants.

Answer

A. Ethylene is a hormone which is gaseous in nature.

B. Auxin (synthetic auxin 2-4 D) is responsible for phototropism and geotropism in plants.

C. Ethylene causes feminising effect. External supply of very small quantity of ethylene can increase the number of female flowers and hence fruits as in cucumber.

D. Synthetic auxin (2-4 D) kills broad leaved dicot weeds, hence used as weedicides.

E. Gibberellins, induces flowering in long-day plants.