Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Tamilnadu State Board New Syllabus Samacheer Kalvi 11th Bio Botany Guide Pdf Chapter 15 Plant Growth and Development  Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 11th Bio Botany Solutions Chapter 15 Plant Growth and Development

11th Bio Botany Guide Plant Growth and Development Text Book Back Questions and Answers

Part – I.

Question 1.
Select the wrong statement from the following.
a) Formative phase of the cells retain the capability of cell division.
b) In elongation phase development of central vacuole takes place.
c) In maturation phase thickening and differentiation
d) In maturation phase, the cells grow further.
Answer:
d) In maturation phase, the cells grow further.

Question 2.
If the diameter of the pulley is 6 inches, length of pointer is 10 inches and distance travelled by pointer is 5 inches. Calculate the actual growth in length of plant.
a) 3 inches
b) 6 inches
c) 12 inches
d) 30 inches
Answer:
(*)
* Answer: options are wrong, (correct Ans = 1.5 inches)
Solution :
Step I:
Diameter of the Pulley=6 inches
Radius of the pulley \(=\frac{6}{2}\)= 3 inches
Actual growth in length= Distance travailed by pointer x Radius of the pulley Length of the pointer
=\(\frac{5 \times 3}{10}\) =1.5=1.5.
Answer:
1.5 inches

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 3.
In unisexual plants, sex can changed by the application of
a) Ethanol
b) Cytokinins
c) ABA
d) Auxin
Answer:
c) ABA

Question 4.
Select the correctly matched one
A) Humanurine i) Auxin-B
B) Corn gram oil ii) GA3
C) Fungs iii) Abscisic acid II
D) Herring fish sperm iv) Kinetin
E) Unripcrnaizegrains v) AuxinA
F) Young cotton boils vi) Zeatin
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 1
Answer:
b) A – v, B – i, C – ii, D – iv, E – vi, F – iii

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 5.
Seed dormancy allows the plants to
a) overcome unfavourable climatic conditions
b) develop healthy seeds
c) reduce viability
d) prevent deterioration of seeds
Answer:
(a) overcome unfavourable climatic conditions

Question 6.
What are the parameters used to measure growth of plants?
Answer:
Growth in plants can be measured in terms, of

  • Increase in length or girth (roots and stems)
  • Increase in fresh or dry weight
  • Increase in area or volume (fruits and leaves)
  • Increase in number of cells produced.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 7.
What is plasticity?
Answer:
Plasticity refers to the environmental heterophylly seen in Butter cup plant (Ranunculus). In this aquatic plant, the leaves in the air is normal, where as the leaves submerged underwater are highly thin and hairy highly adapted to do carbon assimilation Developmental heterophlly seen in the juvenile plant leaves of cotton and corianter. Where the young leaves have a different shape from the mature leaves is not considered as plasticity.

Question 8.
Write the physiological effects of Cytokinins:
Answer:
Promotes cell division:
Cytokinin, in the presence of Auxin (IAA), promotes cell division.

Induction of cell enlargment:
Associated with IAA and Gibberellins induces cell enlargement

Breaks dormancy:
It can break dormancy of certain, light sensitive seeds and induces germination. Eg. Tobacco

Lateral growth:
It promotes the growth of lateral buds even in the presence of Apical bud.

Delays Aging:
It’s application, delays – aging by nutrient mobilization – It is known as Rich mond Lang effect Varrious other activities, such as

  • Increases rate of protein synthesis
  • Induces formation of interfascicular cambium
  • Overcomes apical dominance
  • Induces formation of new leaves, chloroplasts and lateral shoots
  • accumulation of solutes.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 9.
Describe the mechanism of photoperiodic induction of flowering.
Answer:
Mechanism of photoperiodic induction of flowering.

  • The physiological change on flowering due to relative length of light and darkness (photoperiod) is called Photoperiodism.
  • The photoperiod required to induce flowering is called critical day length. Eg. 12 hours in Maryland Mammoth ‘ Tobacco Xanthium 15.05 hours.

Photoperiodic induction:

  • An appropriate photoperiod in 24 hours cycle constitutes one inductive cycle. Plants may require one or more inductive cycles for flowering.
  • The phenomenon of conversion of leaf primordia into flower primordia under the influence of suitable inductive cycles is called photoperiodic induction. Example: Xanthium (SDP) -1 inductive cycle and Plantago (LDP) -25 inductive cycles.

Site of photinductive perception:

  • Leaves are the parts that receive photo periodic stimulus (PPS), again it is only leaves that synthesize floral hormones and tranlocate it to the apical tip to promote flowering.
  • This can be demonstrated by experiments conducted in Cocklebur plant. Which is a SD plant. The nature of flower producing stimulus has been elusive so far. It is believed by phsiologist that a hormone is responsible for it, Chailakyan (1936) named it as Florigen It is not possible to isolate it.
Procedure Observation Inference
1. Take potted plant A and defoliate the plant subject it to SD – condition There is no induction of flowering No leaf to receive stimulus or induction of flowering
2.  Take potted plant B – and defoliate all, except one leaf subject it to SD – condition. There is the induction of flowering One leaf is enough to receive stimulus or induction of flowering.
3.  Take potted plant C – and defoliate it and subject it to LD condition There is no induction of flowering no leaf to receive stimulus or induction of flowering
4. Take potted plant D and subject all leaves to LD but one leaf to SD There is induction of flowering One leaf is enough to receive induction in the SD condition

Question 10.
Give a brief account on programmed cell death (PCD).
Answer:
Getting old or aging is called senescence.

  1. Senescence is controlled by plants own genetic programme and death of the plant or plant part consequent to senescence is called Programmed Cell Death. In short senescence of an individual cell is called PCD.
  2. The proteolytic enzymes involving PCD in plants are Phytapases and in animals are caspases. Lhe nutrients and other substrates from senescing cells and tissues are remobilized and reallocated to other parts of the plant that survives.
  3. The protoplasts of developing xylem vessels and tracheids die and disappear at maturity to make them functionally efficient to conduct water for transport.
  4. In aquatic plants, aerenchyma is normally formed in different parts of the plant such as roots and stems which encloses large air spaces that are created through PCD.
  5. In the development of unisexual flowers, male and female flowers are present in earlier stages, but only one of these two completes its development while other aborts through PCD.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 2

Part-II.

11th Bio Botany Guide Plant Growth and Development Additional Important Questions and Answers

I. Choose The Correct Answer

Question 1.
Geometric growth represents …….. graph
a) J – Shaped
b) S-Shaped
c) bell Shaped
d) liner graph
Answer:
b) S-Shaped

Question 2.
An example for De-Differentiating cell is ………………
a) Tracheary element
b) shoot apex
c) Cork cambium
d) root apex
Answer:
c) Cork cambium

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 3.
Auxin synthesis occurs in
a) root / shoot tips
b) Cortex
c) Xylem
d) Phloem
Answer:
a) root /shoot tips

Question 4
Choose the natural Auxin of the following
a) Anti Auxin
b) NAA
c) 2.4.D
d) IndoleAcetic Acid (IAA)
Answer:
d) Indole Acetic Acid (IAA)

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 5.
The Precursor for plant hormone Gibberellins is
a) Tryptophan
b) Acetyl CoA
c) Succinyl CoA
d) Histidine
Answer:
b) Acetyl CoA

Question 6.
The hormone present in Coconut milk is
a) Gibberellins
b) Ethylene
c) Cytokinin
d) Auxin
Answer:
c) Cytokinin

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 7.
The chemical substance with the molecular structure of carotenoid ………….. is
a) Gibberellins
b) Ethylene
c) ABA
d) Cytokinin,
Answer:
c) ABA

Question 8.
Which of the following Phytóhormone does not occur naturally in plants? .
a) 2. 4. D
b) GibberellicAcid
c) 6. Furfuryl amino purine
d) IAA
Answer:
a) 2.4.D

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 9.
In decapitated plants, axillary buds are activated because,
a) Absence of auxin
b) More food material as available to them
c) Amount of Cytokinin increases in them
d) They get more light
Answer:
a) Absence of Auxin

Question 10.
Apical dominance is caused when Auxin
a) Concentration is more than Cytokinins
b) Concentration is less than Cytokinins
c) and Cytokinin concentration are equal
d) and Cytokinin concentration are fluctuating
Answer:
a) Concentration is more than Cytokinins

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 11.
The synthetic hormone used as weedicide Is
a) Indole -3 Acetic Acid
b) Gibberelic Acid
c) 2- 4 Dichiorophenoxy Acetic Acid
d) Malic hydrazide
Answer:
c) 2- 4 Dichiorophenoxy Acetic Acid

Question 12.
Which prevents premature fall of fruit?
a) NAA
b) Ethylene
c) GA3
d) Zeatin
Answer:
a) NAA

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 13.
In tissue culture, differentiation of root and shoot can be controlled by
a) Modifying Auxm and Cytokinin ratio in the medium
b) Using ABA and Ethylene
c) Giving temperature shocks
d) Changing in light intensity
Answer:
a) Modifying Auxin and Cytokinin ratio in the medium

Question 14.
The term Auxin was coined by
a) Went
b) Darwin
c) Smith
d) Garner
Answer:
a) Went

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 15.
This is an Anti auxin compound
a) 2.4.D
b) TIBA
c) GA3
d) PAA
Answer:
b) TIBA

Question 16.
The term Gibberellin was coined by
a) Went
b) Kurosawa
c) Skoog
d) Yabuta
Answer:
d) Yabuta

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 17.
The term Phytochrome was coined by
a) Garner
b) T.D.Lysenko
c) Skoog
d) Butler
Answer:
d) Butler

Question 18.
The mineral required for synthesis of IAA is
a) Copper
b) Magnesium
c) Zinc
d) Boron
Answer:
c) Zinc

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 19.
Ripe banana contain large amount of
a) ABA
b) IAA
c) IPA
d) Ethylene
Answer:
d) Ethylene

Question 20.
The most widely occuring Cytokinin in plants is
a) ABA
b) NAA
c) TNT
d) IPA
Answer:
d) IPA

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 21.
The term kinetin was coined by
a) Went
b) Haber landt
c) Skoog
d) Kurosawa
Answer:
c) Skoog

Question 22.
The term Florigen was coined by
a) Maheswari
b) Chailakyan
c) R Gane
d) Richmond Lang
Answer:
b) Chailakyan

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 23.
Which of the following types of Phytohormones resemble the nucleic acid in some structural aspects?
a) Cytokinins
b) Auxins
c) Gibbervellins
d) Abscisic acid
Answer:
a) Cytokinins

Question 24.
Which of the following is a bioassay for Cytokinins?
a) Chlorophyll preservation test
b) Dwarf maize Assay
c) Seed germination Assay test
d) Neem cotyledon Assay
Answer:
d) Neem cotyledon Assay

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 25.
Which of the hormone is known as stress hormone?
a) Gibberellin
b) Kinetin
c) ABA
d) Auxin
Answer:
c) ABA

Question 26.
Avena curvature test as an Bio Assay for
a) Auxins
b) GA3
c) Cytokinin
d) Ethylene
Answer:
a) Auxins

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 27.
Which one of the following is Agent orange?
a) Colour used in fluorescent lamp
b) Weddicide with Dioxin
c) Chemical used in luminous paint
d) Bio degradable insecticide
Answer:
b) Weddicide with Dioxin

Question 28.
The Gibberellins have been commercially exploited for
a) increasing the size of grape fruits
b) inducing rooting in stem cuttings
c) breaking the dormancy in seeds
d) production of disease resistant varieties
Answer:
c) breaking the dormancy in seeds

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 29.
To increase sugar production in sugarcane, they are sprayed with
a) IAA
b) Cytokinin
c) Gibberellins
d) Ethylene
Answer:
c) Gibberellins

Question 30.
Biennials can be induced to folower in the firest season itself by treatment with
a) Auxin
b) Kinetin
c) GA
d) ABA
Answer:
c) GA

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 31.
Synergistic effects can be traced in
a) Auxin & Cytokinin
b) Auxin & Gibberellins
c) Abscissic acid & Auxin
d) Ethylene & Auxin
a) I & II
b) II & III
c) III & IV
d) I & IV
Answer:
b) Auxin & Gibberellins

Question 32.
Auxin a was isolated from human urine by
a) F.W. went
b) Charles Darwin
c) Kogl and Haugen Smith
d) Denny
Answer:
c) Kogl and Haugen smith

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 33.
The substance used as chemical warfare weapon in Vietnam war was
a) Auxin
b) 2. 4. D
c) 24. 5. T
d) Agent orange
Answer:
d) Agent orange

Question 34.
The most widely occuring Cytokinin in plants is
a) Indole Acetic Acid (LAA)
b) Indole Butyric Acid (IBA)
c) Pentenyl Adenine (IPA)
d) Naphthalene  Acetic Acid (NAA)
Answer:
c) Pentenyl Adenine (IPA)

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 35.
The role of Ethylene in ripening of lemon is studied by
a) R. Gane
b) Cocken
c) Denny
d) Went
Answer:
c) Denny

Question 36.
Scientists, those who are connected with Ethylene
(I) Denny
(II) R. Gane
(III) Kurosawa
(IV) Cocken
Options:
a) (I) (II) & (III)
b) (II) (III) & (IV)
c) (I) (II) & (IV)
d) (I) (III) & (IV)
Answer:
c) (I)(II)& (IV)

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 37.
The short day plants among the following are
(I) Pea, Barley, Oats
(II) Taobacco, Cocklebur
(III) Soyabean Rice and Chrys anthemum
(IV) Sugarcane and Coleus
Options:
a) (I) & II
b) II & III
c) III & IV
d) I&IV
Answer:
b) II & III

Question 38.
Day neutral plants are
a) Sugarcane & Coleus
b) Bryophyllum& Night Jasmine
c) Wheat, rice & Oats.
d) Potato, Tomato & Cotton
Answer:
d) Potato, Tomato & Cotton

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 39.
The word‘Vernalisation’was coined by
a) Purvis
b) Gamer
c) T-D-Lysenko
d) Butter et-al
Answer:
c) T-D – Lysenko

Question 40.
Xanthium (Cockle bur) requires …………….. hours of light to induce flowering,
a) 12
b) 9
c) 15.05
d) 13.05
Answer:
c) 15.05

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 41.
The hormone that cannot be isolated
a) IAA
b) ABA
c) NAA
d) Florigen
Answer:
d) Florigen

Question 42.
The term Photoperiodism was coined by
a) Went
b) Butler
c) Gamer
d) Skoog
Answer:
c) Garner

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 43.
ABA acts as antagonistic to
a) Ethylene
b) Cytokinin
c) Gibberellic acid
d) IAA
Answer:
c) Gibberellic acid

Question 44.
If a short day plant, flowering is induced by
a) Long nights
b) Photo periods less than 12 hrs
c) Photoperiods shorter than critical value and un interrupted long night
d) Short photo periods and interrupted long nights
Answer:
c) Photoperiods shorter than critical value and un interrupted long night.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 45.
Phytochrome is
a) Reddish phyto hormone
b) Bluish biliprotein pigment
c) Photo receptor of apical bud
d) Unstable pigment molecule
Answer:
b) Bluish biliprotein pigment

Question 46.
The growth & ripening is induced by Ethylene in
a) Tropical fruits
b) Temperate fruits
c) Climacteric fruits
d) Non climacteric fruits
Answer:
c) Climacteric fruits

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 47.
The bio assay of ABA was done with
a) Rice
b) Wheat
c) Maize
d) Barley
Answer:
a) Rice

Question 48.
Four types of senescence was recognised by
a) Leopold
b) Gamer
c) Addicott
d) Cocken etal
Answer:
a) Leopold

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 49.
Final stage of senescence is
a) PCD
b) Scarification
c) Yellowing
d) Abscission
Answer:
d) Abscission

Question 50.
Match & Find out the Correct Answer

Column I Column II
1.  Yabuta&Sumiki a) Identified Ethylene
2.  Lethan & Miller b) Isolated Auxin from Human urine
3.  Cockenetal c) Isolated and identified Zeatin
4.  Kogi & Haugen Smith d) Isolated Gibberellin in Crystal form

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 3
Answer:
b) D C A B

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 51.
Match the following and Find the Correct Answer

I. Auxin a) Bolting
II. ABA b) Induces Respiration
III. Giberellin c) Cell division
IV. Ethylene d) Weedicide
V. Cytokinin e) Closure of stomata

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 4
Answer:
b) D E A B C

II. Assertion (A) & Reason (R)

Question 52.
a. Both A & R are true and ‘R’ is the correct explanation of A
b. Both A & R are true but ‘R’ is not the correct explanation of A
c. A is true but R is False
d. Both A and ‘R’ are False
Assertion (A): The shoot Apical meristems are the only source of Auxin synthesis
Reason (R): Dormancy of lateral buds over Apical buds is due to Auxin
Answer:
C. A is true but R is False

Question 53.
Assertion (A): Hormones are also called Growth regulator
Reason (R): Hormones promote or inhibit plant growth
Answer:
A. Both Assertion (A) an Reason (R) are true and Reason is the correct explanation of Assertion.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 54.
Assertion (A): In many land Mammoth flowering occurred at different times at different latitude
Reason (R): Many land Mammoth is a tobacco variety
Answer:
b. Both Assertion (A) and, Reason (R) are true and Reason is not the correct explanation of Assertion.

2 Mark Questions

III.

Question 1.
Growth is remarkable measurable and significant in some plants Give Egs.
Answer:

  • Growth is measurable
  • One single maize root apical meristem can give rise to more than 17,500 new cells per hour and cells in a
    water melon my increase in size upto 3,50,000 times.
  • Also Bamboos are ever green grasses grow at the rate of 91 cm per day.

Question 2.
Compare between Absolute and Relative growth rates
Answer:

Absolute growth Relative growth
Increase in total growth of two organs measured and compared per unit time is called Absolute growth rate The growth of the given system per unit time expressed per unit initial parameter is called
relative growth rate

Question 3.
What is the speciality of Saguaro Cactus.
Answer:

  • This is a slow growing plant
  • The rate of growth in 1 inch in the first 10 years
  • It flower only about 60 years
  • It takes 75-100 years to grow a side arm
  • Its life span exceeds 150 years.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 4.
Mention the phase of growth in plants
Answer:
I. Formative phase
II. Elongation phase
III. Maturation phase

Question 5.
What is open form of growth of closed form of growth
Answer:

  • Stem and roots are indeterminate in growth due to continuous cell division and is called open form of growth.
  • In leaves, growth is determinate and restricted so known as closed form of growth.

Question 6.
What is Grand period of growth
Answer:

  • The total period form initial to the final stage of growth is called Grand period of growth
  • When plotted against time the growth curve is ‘S’ shaped, (sigma curve) it is also known as Grand Period curie consists of 4 phases
    1.Lag,
    2.Log,
    3.Decelerating,
    4.Maturation.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 7.
What is meant by Etiolation?
Answer:

  • Light is important for growth and formation of Chlorophyll and Photosynthesis
  • Light stimulates healthy growth
  • Absence of light may lead to colour change from green to yellow.
  • This colour change is known as Etiolation.

Question 8.
Define Phytohormone.
Answer:
The chemical substances synthesized by plants and thus naturally occuring are known as Phytohormones. Eg. Auxin, Gibberellins.
Recently 2 groups – Brassinosteroids, Polyamines were also known to behave like hormones.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 9.
Name two Natural Auxins and two synthetic Auxins.
Answer:

  1. Natural  Auxins : PAA, IAA
  2. Synthetic Auxins:
    2.4.D (2.4. Dichlorophenoxy Acetic acid),
    2 4.5.T. (2.4.5 Trichlorophenoxy Acetic acid)

Question 10.
State 3 characteristic features of phyto hormones.
Answer:

  1. They are produced in root tips and stem tips and leaves (do not have specialized cells or organs for secretion)
  2. The transfer of hormones takes place through the conducting system (xylem and phloem)
  3. They are required in trace quantities
  4. They either promote, inhibit or modify growth.

Question 11.
What is Apical dominance?
Answer:
Suppression of growth in lateral bud by apical bud due to Auxin produced by apical bud is termed as Apical
dominance.

Question 12.
Give the historial significance of Agent Orange
Answer:

  • Mixture of two phenoxy herbicides – 2.4. D and 2.4.5 T together known as Agent orange.
  • This Agent orange, was used by USA in Vietnam war as chemical warfare weapon to de foliate forests in Vietnam.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 13.
Does the trimming of plants in gardens have any scientific explanation.
Answer:

  • Yes trimming of plants remove apical buds and hence apical dominance is prevented the lateral buds sprout and give a beautiful bushy appearance and aesthetic value.
  • Also in tea estates, this trimming develop more lateral branches and more tea leaves thus it has commercial signficance.

Question 14.
What is Bakanae or Foolish Seedling disease of paddy?
Answer:

  • This was found by Kurusowa in paddy seeding.
  • Some plant became abnormally tall, which he named as Bakanae disease.
  • Later it was studied that it was caused by Gibbered a fujrkuroi a fungi.
  • The chemical that was isolated from this and was named as Gibberellin by Yabuta (1935).

Question 15.
What is bolting?
Answer:

  • When treated with Gibberellins the rose the plants (genetic dwarf) exhibit excessive inter nodal growth.
  • This sudden elogation of stem followed by flowering is called bolting.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 16.
What is Richmond Lang effect?
Answer:
Application of Cytokinin delays the process of aging by nuitrient mobilization.

Question 17.
Why do we call, ABA as stress hormone?
Answer:

  • ABA inhibit shoot growth and promotes growth of roof system.
  • This character protect the plants from water stress. Hence ABA is called as stress hormone

Question 18.
Define photoperiodism & Critical day length.
Answer:

  • The physiological change on flowering due to relative length of light and darkness (Photosperiod) is called
    Photoperiodism.
  • The photoperiod required to induce flowering is called critical day length Eg.
    1) Mary land mammoth (tobacco variety) require 12 hours of light.
    2) Cocklebur required 15.05 hours of light.

Question 19.
What is meant by Day neutral plants
Answer:
There are no of plants can flower in all possible photoperiods. They are also called photo neutral or Intermediate or Day neutral plants Eg. Tomato, Cotton

Question 20.
What is the importance of photoperiodism
Answer:

  • The knowledge of photoperiodism an important role in hybridization experiments.
  • It is an excellent example of physiological pre conditioning that is using an external factor to induce physiological changes in the plant.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 21.
What is Florigen?
Answer:

  • It is a hormone that is said to induce flowering.
  • Chailakyan first coined the word the isolation of Florigen is so far not possible.

Question 22.
Define Vernalization.
Answer:

  • It is a process by which many annuals and biennials are induced to flower when subjected to low temperature exposure.
  • T.d. Lysenko first used the term.

Question 23.
Explain the hypothesis of phasic development of Lysenko
Answer:
The development of an annual seed plant consists of 2 phases.

  1. Thermostage: The vegetable phase requiring low temperature and suitable moisture
  2. Photo stage: The 2nd phase, which require high temperature for synthesis of Florigen.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 24.
Distinguish between Epigeal and Hypogeal germination.
Answer:

Epigeal Hypogeal
Cotyledons pussed out of the soil Cotyledons remain below the soil due to rapid elongation of epicotyls.
Happens due to the elongation of the hypocotyl Eg. Castor & Bean Eg. Maize

Question 25.
Define seed dormancy and what are its types.
Answer:
The condition of a seed when it fails to germinate even in suitable environmental condition is called seed dormancy.
There are two types
(I) Innate dormancy (II) Imposed dormancy.

Question 26.
What is Scarification?
Answer:

  • By mechanical and chemical treatments like cutting or chipping of hard tough sed coat and use of organic solvents to remove waxy or fatty compounds are called scarification.
  • It is a method of breaking dormancy of the seeds.

Question 27.
Distinguish between Re differentiation and Devernalization.
Answer:

Redifferentiation Devernalization
Differentiated cells after multiplication again lose the ability to divide and mature to perform specific functions, is called Re differentiation.
Eg. Sec.Xylem & Sec.
Phloem The reversal of the effect of vernalization is called Devemalization.

Question 28.
Define Senescence.
Answer:

  • Ageing or getting old is called senescence.
  • It refers to all collective, progressive and deteriorative processes which ultimately lead to complete loss of organization and function (Eg. leaves turn yellow and fall off from plant).

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 29.
What is impactation in seed dormancy.
Answer:

  • In some seeds water and oxygen are unable to penetrate micropyle due to blockage by cork cells.
  • These seeds are shaken vigorously to remove the plug
  • The process of removing the plug or block is called impactation.

Question 30.
What is called stratification in seed dormancy?
Answer:

  • The break dormancy, some plant seeds have to be exposed to well aerated, moist condition under low temperature (0°c to 10°c) for weeks to months.
  • This kind od seed dormancy breaking treatment is known as stratification.
  • The stratified soil layers should be given the low temperature treatment for certain period so as to induce germination.
    Eg. Seeds of Rosaceae plants Apple, Plum, Peach etc.

Question 31.
What are the 4 types of Senescence?
Answer:
Leopold (1961) explained 4 types they are

  1. Overall senescence
  2. Top senescence
  3. Deciduous senescence
  4. Progressive senescence.

Question 32.
What is Abscission layer or Abscission Zone?
Answer:
Abscission is marked internally at the place of petiole by a distince zone of few layers of thin walled cells arranged transversely. This zone is called Abscission Zone, which leads to Abscission of the leaf.

Question 33.
Photo periodic response will not be possible in a defoliated plant. Give scientific reasons.
Answer:
Yes a defoliated plant will not respond to photoperiodic change because the hormonal substance responsible for flowering is present in the leaves of the plant.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 34.
What is gas chromatography?
Answer:

  • It is a bio assay technique by which Ethylene can be measured.
  • It helps in the detection of exact amount of ethylene from different plant tissues like lemon and orange.

Question 35.
Give the occurrence and precursors of Gibberellins and Cytokinins.
Answer:

Character Gibberellins Cytokinin
Occurrence Produced by plant parts like embryo, roots and young leaves near the tip. Immature seeds are rich in Gibberellins. Formed in root apex shoot apex like Auxin. Also formed in buds & young fruits.
Precursor Formed by 5C precursor, Iso prenoidunit called Iso Pentenyl Pyro phosphate (IPP) through a number of inter mediates primary precursor – Acetate. Derived from purine-Adenine.

3 Mark Questions

IV.

Question 1.
Explain Arithemetic growth rate and Geometric growth rate by diagrams.
Answer:
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 6

Question 2.
Explain stages in growth by drawing the sigmoid curve.
Answer:

  • The total period from initial to the final stage of growth is called
    Grand period of growth
  • The graph that is drawn by taking time and rate of growth it is ‘S’ shaped. It is known as sigmoid curve.

It has 4 stages
1. Lag phase
2. Log phase
3. Decelerating phase
4. Maturation phase

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 7

Question 3.
Write the Internal conditions for growth Internal factors:
Answer:

  • Genes
  • Phytohormones
  • C/N Ration: The ratio of carbohydrates and Nitrogenous compounds regulate the specific pattern of growth in plants.

Question 4.
Mention the Agricultural role of Auxin.
Answer:

  • Eradicate weeds: Eg. 2.4 D and 2.4.5.7
  • Formation of seedless fruits: (Partheno carpic fruits) Eg. Synthetic Auxin.
  • Break dormancy
  • Induction of flowering: In pineapple NAA induce flowering
  • Increase the number of female flowers: Eg. Cucubita.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 5.
Write about the history of the discovery of Cytokinin.
Answer:

  • Haberlandt (1913): Presence of cell division inducing substance was demonstrated in coconut milk (liquid endosperm)
  • Skoog & Miller (1954): Auto claved DNA from Herring fish sperm stimulated cell division in tobacco pith cells.
  • Lethan (1963): Introduced the term Cytokinin
  • Lethan & Miller: Isolated & Identified a new Cytokinin called Zeatin from unripe maize grain
  • Most widely occurring cytokinin in plants is, ISO Pentenyl adenine (IPA).

Question 6.
What are the Precursors of Gibberellins.
Answer:

  • Gibberellins are chemically related to terpenoids (natural rubber, Carotenoids and steroids) formed by 5-C precursors and Iso prenoid unit called Iso Pentenyl Pyrophosphate (IPP) through a number of intermediates.
  • The primary precursors is Acetate.

Question 7.
What are the Agricultu ral role of Ethylene.
Answer:
1. Reduces flowering:

  • It normally reduces flowering in plants except in Pine apple & Mango
  • Increases the female flower :
  • It increases the number of female (O) flowers and decrease the number of male (O) flower.
  • Increases yield or production of fruits :
  • Ethylene spray in cucumber crop produces female flowers and increases the yield.

Question 8.
Explain mechanism of Vernalization by Hypothesis of hormonal involvement.
Answer:
I. Vernalization: According to Purvis

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 8

 

 

 

 

II. Devernalization
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 9

 

 

Question 9.
What are the practical application of Vernalization.
Answer:

  • It shortens vegetative period and induces the plant to flower earlier.
  • It increasest he cold resistance of the plants.
  • It increasest he resistance of plants to fungal disease.
  • Plant breeding can be accelerated.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 10.
What is meant by viability of seeds.
Answer:

  • Viable means living condition of seed
  • The shell life of the seed after which it cannot germinate is known as viable period
  • It varies from plant to plant
Name of the plant Viability
1. Oxalis seeds Few days
2.  Lotus seeds More than 1000 years
3.  Judean Dale palm (Methuselah) More than 2000 years

Question 11.
Differentiate between climacteric and Non climacteric fruits.
Answer:

Climacteric fruits Non Climacteric fruits
1.There is a sharp rise in respiation rate near the end of the development of fruit.
2. The ripening on demand can be induced in these fruits by exposing them to normal air conditioning.
3. Epthan secrete Ethylene continuously about 1 ppm of ethylene Eg. Lemon, Apples, Banana, Mango
These fruits cannot be ripened by exposure to ethylene so known as non climacteric fruits.
Eg. Grapes, Water melon orange.

Question 12.
Differentiate between scarification & Stratification in breakign seed dormacy
Answer:

Scarification Stratification
Mechanical and chemical treatment either by cutting, chipping or use of organic solvents to remove waxy or fatty compounds are called scarification. Rosceceous plants (Apple, Plum Peach and Cherry) will not germinate until they have been exposed to well derated, moist condition under low temperature (1°c to 10°c) for weeks to months and this treatment is known as  stratification.

Question 13.
What is the physiology of senescence.
Answer:

  • Change in structure of cells
  • Vacuoles act like lysosome – secrete hydrolytic enzymes.
  • Reducation in photosynthetic rate (due to loss of chlorophyll & accumulation of anthocyanin)
  • Decrease in — Starch content, Protein content
  • Decrease in r RNA level due to increased activity of enzyme RNA ase
  • Degeneralion of DNA – by increased activity of enzyme DNA ase

Question 14.
What are the factors that affect senescence.
Answer:

Name of the factor Effect of senescence
ABA & Ethylene Accelerates
Auxin & Cytokinin Nitrogen deficiency reduces increases
Nitrogen supply retards
High temperature in vernalized seeds Accelerates
Low temperature Retards
Water stress Accumulation of ABA leading to senescence

Question 15.
What are the morphological and Anatomical changes due to Abscission?
Answer:

  • Abscission Zone: formed at the base of petiole
  • Greenish grey in colour by rows of 2 to 15 cells thick primary wall and middle lamella
  • The dissolution of by pectinase & Cellulase
  • Formation tyloses – that block conduction of vessels
  • Degradation of chlorophyll – Colour of leaves changes and leaves fall off.
  • After Abscission – Suberization of outer layer of cells by the development of periderm.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 16.
Write down the significance of Abscission.
Answer:
1. Abscission separates dead parts of the plant like old leaves and ripe fruits.
2. Helps in dispersal of fruits and continuing the life cycle.
3. Abscission of leaves (in deciduous plants) helps in water conservation during summer.
4. Helps in vegetative propagation (Shedding of gemmae or plantlets) Eg. Bryophyta.

5 Mark Questions

V.

Question 1.
Describe an Experiment to measure the growth of a plant or By lever Auxanometer measure th erate of growth in stem tip.
Answer:
Experiment:
1. Arc auxanometer:
The increase in the length of the stem tip can easily by measured by an arc auxanometer. If consists of a small pulley to the axis of which is attached a long pointer sliding over a graduated arc. A thread one end of which is tied to the stem tip and another and to a weight passes over the pulley tightly. As soon as the stem tip increases in length, the pulley moves and the pointer slide over the graduated arc (Refer Figure) The reading is taken. The acutal increase in the lengthwm^ stem is then calculated by knowing the length of the pointer and the radius of the pulley. If the radius of the pulley is 4 inches and the length of pointer 20 inches the actual growth is measured as follows:
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 10

Actual growth in length\(=\frac{\text { Dis tan ce travelled by the point er radius of the }}{\text { Length of the point er }}\)
For example, actual growth in length \(=\frac{10 \times 4 \text { inches }}{20 \text { inches }}\)
= 2 inches

Question 2.
Explain the physiological effect of Auxin? Add a note on its agricultural applications.
Answer:
Cell elongation:
Promotes cell elongation in stem & Coleoptile

Root growth:
At extermely low concentration – promote root growth, at high concentrations it inhibit elongation of roots, but induce more latemal roots

Apical dominance:
Suppression of growth of latemal buds – by apical bud is known as Apical dominance
Prevents Abscission

Secondary growth
Promotion of cell division in cambium, responsible for secondary growth this property is exploited in tissue culture. (Callus fonnation)

Respiration Stimulates respiration Induces Vascular differentiation.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 3.
Give the Agricultural application of Auxin.
Answer:
Weedicide
2.4.D & 2.4.5. T – Weedicides to remove weeds

Induce parthenocarpy
Synthetic auxins used to induce parthenocarpy (formation of seedless fruits).

Break dormancy
Used to break seed dormancy.

Induce flowering in Pine apple Eg. NAA & 2.4.D

Induce female flowers (numbers)
Eg. Cucumber.

Question 4.
Explain physiological effects of Gibberellins
Answer:

  • Induction of cell division & cell elongation – Extra ordinary stem elongation.
  • Reversal of dwarfism & Bolting – Rosette (genetic dwarfism) plants when treated with Gibberellins exhibit excessive enter nodal grwoth – This sudden elongation of stem followed by flowering is called Bolting.
  • Breaks dormancy – in Potato tubers.
  • Biennials flower in the 1 st year – Instead of cold exposure, if biennials treated with Gibberellins flowr in the 1st year it self.

Question 5.
Write down the Agricultural role of gibberellins.
Answer:

  • Induces parthenocarpy – (Seed less fruits) Eg. Tomato, Apple & Cucumber
  • Promotes the formation of male flowers Eg. Cucurbitaceae
  • Increases uniform bolting & uniform seed production.
  • Increases yield also increase the number and size of fruits in grapes
  • Increases elongation of sugar cane inter nodes
  • Promotes flowering in L.D. Plants even under S .D. conditions.
  • Stimulates seed germination.

Question 6.
Explain the physiological Effects of Cytokinins.
Answer:

  • With IAA – Promotes cell division With IAA & GA – Induces cell enlargement
  • Breaks dormancy of light sensitive seeds (tobacco) induces seed germination.
  • Promotes growth of lateral
  • buds even in the presence of apical bud.
  • Delays the process of aging by nuitrient mobilization – known as Richmond Lang effect.
  • Induces rate of protein synthesis.
  • Induces formation of interfascicular cambium Over comes apical dominance
  • Induces formation of new leaves chloroplast and lateral shoots.
  • Induces Accumulation of solutes.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 7.
Write down the physiological effects of Ethylene
Answer:

  • Stimulates respiration and there by ripening of fruits
  • Stimulates radial growth in stem and root and inhibits linear growth.
  • breaks dormancy of
    1.buds
    2. Seeds
    3. Storage Organs
  • Stimulates abscission 2 one formation in
    1. leaves
    2. flowers
    3. fruits
    (so leaves shed prematurely)
  • Prevents stem elongation by preventing inter nodal growth
  • Root growth in low concentration
    Stimulates growth of lateral roots and root hairs and increase absorptive surface ‘
  • Ripening of fruits – Increases ripening in climacteric fiuits (Mango, banana) etc.
  • It causes epinasty

Question 8.
Give the physiological effects of ABA Closure of stomata
Answer:

  • ABA inhibit K+ uptake by guard calls and promotes the leakage of malic acid lead to closure of stomate and reduces transpiration rate.
  • It result in loss of turgor pressure and closure of stomata, thus helps in sol ving water stress dirung drought condition (stress – phytohormone)

Changes leaf colour to yellow :
It spoils chlorophylls, proteins and nucleic acids and turn leaves into yellow.

  • Inhibitor of growth
  • Inhibit cell division and cell elongation
  • It causes 50% inhibition of growth in oat coleoptiles
  • Induces bud & seed dormancy
  • Promotes abscission of
    1. leaves
    2. fruits
    3. flowers

Promotes senescence
Causing loss of chlorophyll pigment drcreasing rate of photosynthesis, rate of protein synthesis and nucleic acid synthesis causing senescence.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 9.
Define photoperiodism – Classify plants based on photoperiodism
Answer:
a. The physiological change on flowering due to relative length of light and darkness is called photoperiodism.

  • Gamer and Allard (1920) coined the term
  • They studied photo periodism in Biloxi variety of soy bean (Glycine max) and Mrny land mammoth variety of tobacco.

b. Depending on photo periodic responses plants are classified into several types.
1. L.D. Plants (Long Day) The photo period required to induce flowering is called critical day length depending on critical day length if it is long (more than 12 hours) and with short nights. Eg. Pea Barley and Oats
Short LD Plants: These are Long day plants but need short day length during early period of growth for flowering Eg. Wheat, Rye

2. SD Plants: Plants requiring short critical day length for flowering or long night.
Eg. Tobacco, Cocklebur, Soya, Rice and Chrysanthemum.
Long SD Plants: Actually SD plants but need long days during early period of growth for flowering Eg. Some sps of Bryophyllum & Night Jasmine.

3. Intermediate day plants:
These require a photo period between long day and short day for flowering Eg. Sugarcane and coleus.

4. Day Neutral plants:
There are a number of plants which can flower in all possible photo periods, known photoneutral or hiterterminate plants. Eg. Potato, Rhododendron, Tomato & Cotton.

Question 10.
Describe the role of phytochrome in inducing Flowering
Answer:
Definition:
It is a bluish biliprotein responsible for the perception of light in photophysiological process, existing in two different forms is mainly involved in flower induction, (i.e) Pr and PFr.

  • Butler et-al(1959) named the pigment.
  • It exists in two inter convertible forms
Pr PFr
1. red light absorbing form
2. Absorbs red lgiht of wave length 660 nm
3. Biologically inactive form & stable found in diffused state in cytoplasm
4. Promotes flowering in SD plants and inhibit flowering LD plants.
1. Far red light absorbing form
2. Absorbs far red light of wave length 730 nm
3. Biologically active and it is unstable Associated with hydrophobic area of membrane system
4. Promotes flowering in LD plants and unhibit flowering in SD plants.

Mechanism:
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 14
Other functions:
Play a role in seed germination and changes in membrane conformation.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 11.
Write an Essay on Vernalization
Answer:
Definition:

  • Many biennials and perrennials are induced to flower by low temperature exposure (O°c to 5°c) This process is called Vernalization.
  • T.D. Lysenko – Coined the term.

Mechanism of Vernalization:
2 theories explain the mechanism of vernalization.
1. Hypothesis of Phasic development (T.D. Lysenko),
Development of annual plant has 2 phases.
1. Thermostate-Vegetatine stage requiring low temperature and suitable moisture.
2. Photo stage -high temperature need to synthesize florigen.

2. Hypothesis of hormonal involvement (Purvis 1961)

Vernalization has several steps
Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development 15

Technique of Vernalization:

  • Seeds soaked in water
  • Allowed to germinate at 10°C to 12°C
  • Transferred to low temperature for few days to 30 days (3°C to 5°C).
  • Germinated seeds after the low temp, treatment are allowed to dry & then sown.
  • Quickened flowering than untreated (control seedling)

Devernalization:
Reversal of the effect of vernalization is called Devemalization.

  • Practical Applications:
  • Vernalization shortens the vegetative period and induces the plant to flower earlier
  • It increases cold resistance ’
  • It increase fungal resi stance
  • It accelerates Plant Breeding.

Question 12.
Define Senescence and give its types
Answer:
Definition:
Getting old or Ageing is call d senescence in plants.
It refers to all collective, progressive and deteriorative processes which ultimately lead to complete loss of organization and function.
Types – 4 types (Leopold -1961)

  1. Over all senesence
  2.  Top senescence
  3. Deciduous senescence
  4. Progressive senescence

1. Overall senescence :
When entire plant gets affected and dies – Eg. Annuals – Wheat & Soyabeans, Perrennials – Agave & Bamboo
2. Top senescence :
Occur in aerial parts only Eg. Parrennials – Banana and Gladiolus
3. Deciduous senescence :
Occur only in leaves Eg. Decidual plants – Elm and Maple
4. Progressive Senescence :
Occur in Annuals occur in old leaves first followed by new leaves than stem and finally root system.

Samacheer Kalvi 11th Bio Botany Guide Chapter 15 Plant Growth and Development

Question 13.
Explain the physiology of senescence and Factors affecting senescence Physiology of Senescence :
Answer:

  • Change in structure of cells
  • Vacuoles act like lysosome-secrete hydrolytic enzymes.
  • Reducation in photosynthetic rate (due to loss of chlorophyll & accumulation of anthocyanin)
  • Decrease in Starch content,  Protein content
  • Decrease in …………. r RNA level due to increased activity of enzyme RNA ase
  • Degeneralion of DNA – by increased activity of enzyme DNA ase

Factors affecting senescence :

Name of the factor Effect of senescence
ABA & Ethylene Accelerates
Auxin & Cytokinin Nitrogen deficiency reduces increases
Nitrogen supply retards
High temperature in vernalized seeds Accelerates
Low temperature Retards
Water stress Accumulation of ABA leading to senescence

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