Chapter 13: Plant Growth and Development

Question 1

Development is the sum of two processes : Growth and __________________

Answer 1

differentiation

Question 2

Plant growth is unique because plants retain the capacity for _______________ growth throughout their life

Answer 2

unlimited

Question 3

The ability for unlimited growth of the plants is due to the presence of ________________ at certain locations in their body.

Answer 3

meristems

note:- The cells of such meristems have the capacity to divide and self-perpetuate.

Question 4

This Form of growth wherein new cells are always being added to the plant body by the activity of the meristem is called the ___________ form of growth.

Answer 4

open

Question 5

In dicotyledonous plants and ________________ , the lateral meristems, vascular cambium and cork-cambium appear later in life.

Answer 5

gymnosperms

Question 6

lateral meristems, vascular cambium and *cork-cambium are the meristems that cause the increase in the _____________ of the organs in which they are active. This is known as ______________ growth of the plant.

Answer 6

girth

secondary growth

Question 7

____________, at a cellular level, is principally a consequence of increase in the amount of protoplasm

Answer 7

Growth

Question 8

One single maize root apical meristem can give rise to more than _____________ new cells per hour whereas cells in a watermelon may increase in size by upto ____________ times.

Answer 8

17500
3 50 000

Note:- In the former, growth is expressed as increase in Cell number, the latter expresses growth as increase in size of the cells

Question 9

The period of growth is generally divided into Three phases, namely meristematic, elongation and ________________

Answer 9

maturation

Question 10

The increased growth per unit time is termed as _______________

Answer 10

growth rate

Question 11

The growth rate shows an increase that may be ___________ or ____________

Answer 11

arithmetic
geometrical

Question 12

In ______________ growth, following mitotic cell division, only one daughter cell continues to divide while the other differentiates and matures*

Answer 12

Arithmetic

note:- The simplest expression of arithmetic growth is exemplified by a root elongating at a constant rate.

Question 13

On plotting the length of the organ against time, a ___________ curve is obtained in arithmetic growth

Answer 13

Linear curve*

Question 14

In geometrical growth the initial growth is slow (________ phase), and it increases rapidly thereafter at an exponential rate (________ or Exponential phase), with limited nutrient supply, the growth slows down leading to a ____________ phase.

Answer 14

Lag phase
Log phase
Stationary phase

Question 15

Linear growth is expressed as formula ______________

Answer 15

L_t = L₀ + rt

L_t = length at time ‘t’
L₀ = length at time ‘zero’
r = growth rate/ elongation per unit time.

Question 16

The exponential growth can be expressed as ______________

Answer 16

W₁= W₀ e^rt
W₁= final size (weight, height, number etc)
W₀= initial size at the beginning of the period
r = growth rate
t = time of growth
e = base of natural logarithms

Question 17

______________ is the process where cells specialize and acquire unique functions.

Answer 17

Differentiation

example :-The formation of tracheary elements in xylem is a classic example of plant cell differentiation, where specialized cells with unique functions are produced.

Question 18

______________ is when specialized cells revert to a less specialized state, often becoming meristematic.

Answer 18

Dedifferentiation

example:- The formation of vascular cambium and cork cambium from fully differentiated parenchyma cells is an example of dedifferentiation, where cells lose their specialized functions and become meristematic.

Question 19

_____________ is the subsequent process where these cells regain their specialized functions.

Answer 19

Redifferentiation

example:- The vascular cambium, after dedifferentiation, redifferentiates to produce secondary xylem and phloem, where the cells regain their specialized functions of water and food conduction, respectively

Question 20

Plants follow different pathways in response to environment or phases of life to form different kinds of structure. This ability is called _______________

Answer 20

Plasticity

ex:- **heterophylly in Cotton, coriander and larkspur. IN such plants, the leaves of the juvenile plant are different in shape from those in mature plants.

Question 21

Difference in shapes of leaves produced in air and those produced in water in buttercup also represent the heterophyllous development due to environment this phenomenon of heterophylly is an example of ___________________

Answer 21

Plasticity

Question 22

The plant growth regulators (PGR_s) are small, simple molecules of diverse chemical composition.They could be

1. indole compounds (_____________)
2. adenine derivatives(_____________)
3. derivatives of carotenoids(___________)
4. terpenes(_______________)
5. gases (______________)

Answer 22

1. indole compounds (Indole-3 -acetic acid, IAA)
2. adenine derivatives( N⁶-furfuryl amino purine, kinetin)
3. derivatives of carotenoids(abscisic acid, ABA)
4. terpenes(gibberellic acid, GA₃)
5. gases (ethylene , C₂H₄)

Question 23

The PGR_s can be broadly divided into two groups based on their functions in a living plant body. One groups of PGR_s are involved in growth promoting activities , such as Cell division, cell enlargement, pattern formation, tropic growth, flowering , fruiting and seed formation. These are also called plant growth promoters

ex: - ______________ ,_______________ and __________________

Answer 23

Auxins
gibberellins
cytokinins*

Question 24

The PGR_s of the other group play an important role in plant responses to wounds and stresses of biotic and abiotic origin. They are also involved in various growth inhibiting activities such as _____________ and _________________

Answer 24

dormancy
abscission

Note:- The PGR abscisic acid belongs to this group. The gaseous PGR, *ethylene, could fit either of the groups, but it is largely an inhibitor of growth activities.

Question 25

**Auxin** was isolated by ________________ from tips of coleoptiles of **oat seedlings**.

Answer 25

**F.W Went**

Question 26

The ***'bakanae'*** (foolish seedling) disease of **rice** seedlings, was caused by a **fungal pathogen** ***Gibberella fujikuroi.*** _______________ reported the appearance of symptoms of the disease in rice seedlings when they were treated with sterile filtrates of the fungus. The active substances were later identified as _______________

Answer 26

**E. Kurosawa (1926)** **Gibberellic acid**

Question 27

_____________ and his co-workers observed that from the **internodal segments** of tobacco stems the **callus**(a mass of undifferentiated cells) proliferated only if, in addition to ***auxins** the nutrients medium was supplemented with one of the following extracts of vascular tissue, yeast extract, **coconut milk or DNA**

Answer 27

**F. Skoog** Note:- **Miller et al. (1955)**, later identified and crystallised the cytokinesis promoting active substance that they termed **kinetin**

Question 28

During mid-1960, three independent researches reported the purification and chemical characterisation of three different kinds of inhibitors: _______________ ,____________________ and ______________. Later all the three were proved to be chemically identical. It was named **abscisic acid (ABA)**

Answer 28

**inhibitor-B** **abscission II** **dormin**

Question 29

______________ confirmed the release of a volatile substance from ripened oranges that hastened the ripening of stored unripened bananas. Later this volatile substance was identified as _____________, a gaseous **PGR**

Answer 29

**H.H. Cousins (1910)** **ethylene**

Question 30

**Auxins** (from Greek 'auxein': to grow) was first isolated from ____________.The term 'auxin' is applied to the ***indole-3-acetic acid (IAA)**

Answer 30

**Human urine**

Question 31

**Auxins** like **IAA** and _______________ have been isolated from **Plants**.

Answer 31

**indole butyric acid (IBA)**

Question 32

**NAA (naphthalene acetic acid)** and **2,4-D(2,4-dichlorophenoxyacetic) are _______________ auxins.

Answer 32

**synthetic auxin**

Question 33

_____________ help to initiate rooting in **Stem cuttings**, an application widely used for plant propagation.

Answer 33

**Auxins**

Question 34

_____________ promote flowering e.g. in **pineapples**.

Answer 34

**Auxins**

Question 35

____________ help to prevent fruit and leaf drop at early stages but promotes the **abscission** of older mature leaves and fruits.

Answer 35

**Auxins**

Question 36

In most higher plants, the growing **apical bud** inhibits the growth of the lateral (axillary) buds, a phenomenon called ___________________

Answer 36

**apical dominance**

Question 37

_____________ also induce **parthenocarpy**, e.g., in **tomatoes**

Answer 37

**Auxins**

Question 38

**Auxins** are widely used as **herbicides** , _____________ widely used to kill **dicotyledonous weeds** does not affect mature **monocotyledonous plants**.

Answer 38

**2, 4-D** (2,4-dichlorophenoxyacetic)

Question 39

**Gibberellins** are another kind of promotory **PGR***. There are more than ___________ gibberellins reported from widely different organisms such as **Fungi** and **higher plants**. They are denoted as **GA₁,GA₂,GA₃** and so on.

Answer 39

**100**

Question 40

**Gibberellic acid**(________) was one of the first gibberellins to be discovered and remains the most intensively studied form.

Answer 40

**GA₃**

Question 41

All **GA_s** are ____________. They produce a wide range of physiological responses in the plants.

Answer 41

**Acidic**

Question 42

**Gibberellins** ability to cause an increase in length of axis is used to increase the length of _____________ stalks. Gibberellins, cause fruits like ___________ to **elongate** and **improve its shape**.

Answer 42

**Grapes stalks** **Apple** note:- Gibberellins also delay senescence , Thus the fruits can be left on the tree longer so as to extend the market period.

Question 43

______________ is used to speed up the **malting process** in brewing industry.

Answer 43

**GA₃**

Question 44

**Spraying** sugarcane crop with ____________________ increases the length of the stem, thus increasing the yield by as much as _________ tonnes per acre.

Answer 44

**Gibberellins** **20**

Question 45

_____________ promotes **bolting** (internode elongation just prior to flowering) in **beet**, **Cabbages** and many plants with rosette habit.

Answer 45

**Gibberellins**

Question 46

**Cytokinins** have specific effects on **cytokinesis**, and were discovered as _________________( a modified form of adenine, a purine) from the autoclaved herring **Sperm DNA**

Answer 46

**Kinetin** Note:- Kinetin does not occur naturally in **plants**.

Question 47

Natural substances with **cytokinin**-like activities found in ____________ from **corn-kernels and coconut milk**.

Answer 47

**Zeatin**

Question 48

Natural **Cytokinins** are synthesised in region where rapid ______________ occurs, ex:- root apices, developing shoot buds, young fruits etc.

Answer 48

**Cell division**

Question 49

______________ help overcome the **apical dominance**

Answer 49

**Cytokinins**

Question 50

____________ is a simple gaseous **PGR**

Answer 50

**Ethylene**

Question 51

Ethylene is synthesised in large amounts by tissues undergoing **Senescence** and _______________ fruits

Answer 51

**ripening fruits**

Question 52

**Ethylene** promotes senescence and abscission of plant organs especially of ____________ and _______________

Answer 52

**leaves** **flowers**

Question 53

Ethylene is highly effective in **Fruit ripening**. It enhances the respiration rate during ripening of the fruits. this rise in rate of respiration is called ___________________

Answer 53

**respiratory climactic**

Question 54

**Ethylene** breaks seed and bud ____________, initiates germination in **peanut seeds**, **sprouting of potato tubers**. Ethylene promotes rapid internode/petiole elongation in deep water ___________ plants.

Answer 54

**Dormancy** **Rice**

Question 55

_________________ also promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.

Answer 55

**Ethylene**

Question 56

Ethylene is used to initiate flowering and for synchronising fruit-set in ____________. It also induces flowering in ______________

Answer 56

**Pineapples** **Mango**

Question 57

The **most widely** used **compound** as source of **Ethylene** is ________________

Answer 57

**ethephon**

Question 58

Ethylene promotes female flowers in _______________ thereby increasing the yield.

Answer 58

***cucumbers***

Question 59

Abscisic acid (**ABA**) was discovered for its role in regulating **abscission** and ________________

Answer 59

**dormancy**

Question 60

**ABA** acts as a general plant growth ____________ and an inhibitor of plant **metabolism**.

Answer 60

**inhibitor**

Question 61

**ABA** inhibits seed **germination**. **ABA** stimulates the closure of **Stomata*** and increases the tolerance of plants to various kinds of stresses, therefore , it is also called the ______________ hormone.

Answer 61

**Stress hormone**

Question 62

______________ acts as an **Antagonist** to **GA_s**

Answer 62

**ABA**