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Internal structure of monocot leaf - class-XI

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Which one is correct about bulliform/ motor cell?

  1. It is seen in grasses.

  2. It is large-sized, colorless, vacuolate cells on the adaxial surface of monocot leaf.

  3. Both of the above

  4. None of the above


Correct Option: C
Explanation:

Bulliform cells or the motor cells are the modified epidermal cells present on the upper surface or the adaxial surface of the monocot leaf (the grasses). They are colourless, large-sized and vacuolated cells. They regulate the rolling of leaves to prevent the loss of water. When water is adequately present, they become turgid and keep the leaf open and exposed. When there is scarcity of water, the become flaccid and roll-up the leaf to prevent the loss of water.

Hence, the correct nswer is 'Both of the above'

Which one describes the correct features of plant leaves?

  1. Hair on the lower surface and waxy cuticle

  2. Hair on the upper surface an no cuticle

  3. Epidermis without stomata

  4. Presence of endodermis and casparian strips


Correct Option: A
Explanation:

  • Leaves have a layer of waxy cuticle on their surface as it helps in preventing water loss due to excess transpiration. The leaves may also have hair on the lower surface which act as trichomes and protect the surface of the leaves.
  • The epidermis of the leaves has minute pores called stomata through which gaseous exchange takes place.
  • Endodermis and Casparian strips are present in the roots of the plants.
So, the correct answer is 'Hair on the lower surface and waxy cuticle'.

Isobilateral leaf is characterised by

  1. Similarly green two surfaces

  2. Amphistomatic nature

  3. Undifferentiated mesophyll

  4. All the above


Correct Option: A
Explanation:

Leaf, in which both surfaces are similar in appearance are called isobilateral leaves. These are found in monocotyledons. It is due to the presence of spongy parenchyma.

So, the correct option is ‘Similarly two green surfaces’.    

What differentiates a dicot leaf from monocot leaf?

  1. Stomata only on upper side

  2. Differentiation of palisade and spongy parenchyma

  3. Parallel venation

  4. Stomata on upper and lower sides


Correct Option: B
Explanation:

Dicot leaf differs from monocot leaf anatomically in terms of presence of more number of stomata in the lower epidermis, presence of differentiated mesophyll,  and vascular bundle.

So, the correct option is 'Differentiation of palisade and spongy parenchyma'.

Isobilateral leaves have stomata on

  1. Both upper and lower surfaces

  2. Upper surface only

  3. Lower surface only

  4. None of the two surfaces


Correct Option: A
Explanation:

In isobilateral leaves or monocot leaves, stomata are present on both upper or adaxial epidermis as well as lower epidermis or abaxial epidermis.

So, the correct option is ‘Both upper and lower surfaces’.

An undifferentiated mesophyll is found in

  1. Isobilateral leaves

  2. Dorsiventral mesophytic leaves

  3. Dorsiventral xerophytic leaves

  4. Vertical leaves


Correct Option: A
Explanation:

A.Isobilateral leaves – Mesophyll is undifferentiated, contains spongy parenchyma only.

B.Dorsiventral mesophytic leaves – Mesophyll is differentiated into upper palisade parenchyma and lower spongy parenchyma.

C.Dorsiventral xerophytic leaves – Mesophyll is differentiated into upper and lower palisade parenchyma and middle spongy parenchyma.

D.Vertical leaves - Mesophyll is differentiated into upper and lower palisade parenchyma and middle spongy parenchyma.

So, the correct option is ‘isobilateral leaves’.

Which of the following is true about a monocot leaf?

  1. Reticulate venation

  2. Absence of bulliform cells from epidermis

  3. Mesophyll not differentiated into palisade and spongy tissues

  4. Well differentiated mesophyll


Correct Option: C
Explanation:

In the monocot leaf, mesophyll is undifferentiated, shows spongy parenchyma with oval-shaped cells.

So, the correct option is ‘Mesophyll not differentiated into palisade and spongy tissues'.

Bulliform cells differ from other cells in being

  1. Large, thin-walled, vacuolate containing water

  2. Large, thick-walled, contain abundant chloroplasts

  3. Small, thick-walled, contain starch

  4. Small, thin-walled, contain calcium oxalate


Correct Option: A
Explanation:

The large sized, thin-walled, vacuolated, water containing colourless epidermal cells present on the adaxial epidermis of an isobilateral leaf or monocot leaf are called Bulliform cells. They differ from other cells in being size, structure and function.

So, the correct option is ‘large, thin-walled, vacuolated containing water’

Bulliform or motor cells are present on.

  1. Root

  2. Stem

  3. Isobilateral leaf

  4. Dorsiventral leaf


Correct Option: C
Explanation:

The large sized, thin-walled, water containing colourless epidermal cells present on the adaxial epidermis of an isobilateral leaf or monocot leaf are called bulliform cells.

So, the correct option is ‘Isobilateral leaf’.

Bundle sheath extensions in a dicot leaf and in a monocot leaf are ________ and ________ respectively.
  1. Parenchymatous, Collenchymatous

  2. Parenchymatous, Sclerenchymatous

  3. Sclerechymatous, Parenchymatous

  4. Collenchymatous, Sclerenchymatous


Correct Option: B
Explanation:
  • In dicot leaf, bundle sheath is generally single-layered and formed of colourless cells. Bundle sheath extensions are parenchymatous. 
  • In monocot leaf, bundle sheath may be single or double layered and the cells generally possess chloroplasts. Bundle sheath extensions are sclerenchymatous.
Thus, the correct option is (B).

Amphistomatic leaf, with stomata distributed equally on both the surfaces, is an example of ______________.

  1. Isobilateral leaf

  2. Dorsiventral leaf

  3. Xerophytic leaf

  4. Hydrophytic leaf


Correct Option: A
Explanation:

Leaf having stomata equally distributed on both surfaces is called amphistomatic (isobilateral) leaf, e.g., most monocot leaves.

In grass, ligule occurs on

  1. Sheathing leaf base

  2. Leaf blade

  3. Petiole

  4. Between sheathing leaf base and leaf blade


Correct Option: D
Explanation:

A ligule is a thin outgrowth which is found at the junction of sheathing leaf base (leaf base is broad and surrounds the stem as an envelope) and leaf blade. It is commonly a form of a translucent membrane or a fringe of hairs. The ligule appears to be a continuation of the leaf sheath and encircles the stem as done by the leaf sheath.

So, the correct answer is 'Between sheathing leaf base and leaf blade'.

Monocot leaves possess

  1. Intercalarly meristem

  2. Lateral meristem

  3. Apical meristem

  4. Mass meristem


Correct Option: A
Explanation:
  • The shoots can be categorized as long shoots and short shoots (on the basis of the distance between two nodes).
  • Internode is the length of the stem between two nodes.
  • The variable length of internodes in culm of sugarcane is mainly due to the presence of intercalary meristem (residual apical meristem).
  • An intercalary meristem is the meristems present at the base of the internodes of stem or leaf.
  • It helps in the elongation and growth of the plants at the nodes and internodes (stems and leaves).
  • In monocots such as in grasses it enables longitudinal growth of the leaves and in hollow stem or culm of bamboo and sugarcane, it helps in increasing the length of the stems.
  • So, the correct answer is 'Intercalary meristem'.

Leaves of many grasses are capable of folding and unfolding because they

  1. Are very thin

  2. Are isobilateral

  3. Have specialised bulliform cells

  4. Have parallel vascular bundles


Correct Option: C
Explanation:

Grasses have monocot leaves. Leaves of grasses have specialized bulliform cells on the upper epidermis. These bulliform cells are capable of folding and unfolding of leaves to help in the process of transpiration. 

Thus, the correct answer is option C.

Ligule occurs on the leaf of

  1. Barley

  2. Oat

  3. Rice

  4. All of the above


Correct Option: D
Explanation:

The ligule is a part of the leaf that is found at the junction of the leaf blade and sheath of the leaf. It may take several forms. But commonly, it is a translucent membrane or a fringe of hairs. It is seen in plants belonging to the family Poaceae. Hence, ligule occurs on the leaf of Barley, Oat and Rice.

So, the correct answer is 'All of the above'.

Many grass leaves are capable of folding and unfolding due to

  1. Parallel veins

  2. Isobilateral nature

  3. Thin lamina

  4. Bulliform cells


Correct Option: D
Explanation:

Many grass leaves, folds during drought conditions and unfolds during moisturized conditions. It is due to the presence of large, thin-walled cells present on the adaxial side of the upper epidermis, called Bulliform cells.

So, the correct option is ‘Bulliform cells’.

In isobilateral leaves

  1. Lower surface is brighter green

  2. Upper surface is lighter green

  3. Both the surfaces are equally green

  4. Upper surface is dark green while the lower surface is lighter green


Correct Option: C
Explanation:

Leaves, in which both sides appear in equally green color are called isobilateral leaves. It is due to the presence of spongy parenchyma.

So, the correct option is ‘both the surface are equally green’.

Bulliform or motor cells occur in

  1. Upper epidermis of dicot leaves

  2. Upper epidermis of monocot leaves

  3. Lower epidermis of monocot leaves

  4. Lower epidermis of dicot leaves


Correct Option: B
Explanation:

Bulliform cells or motor cells are large, bubble shaped epidermal cells that occur in groups on the upper surface of the leaves of many grasses. Loss of turgor pressure in these cells causes leaves to roll up during water stress. During drought, the loss of moisture through vacuoles induces bulliform cells to cause the leaves of many grass species to close as the two edges of the grass blade fold up toward each other. Once, adequate water is available, these cells enlarge and the leaves open again. Bulliform cells are absent in dicot leaves. 
Thus, the correct answer is option B.

Dorsiventral leaf is identified by the presence of

  1. Stomata on both the epidermis

  2. Stomata mainly present on the lower epidermis

  3. No stomata on the epidermis

  4. Sunken stomata on the upper epidermis


Correct Option: B
Explanation:

In dorsiventral leaf, epidermis is in two layers, one on each surface of the leaf. Both the layers are composed of compactly arranged, barrel-shaped cells. Intercellular spaces are absent. A cuticle surrounds both the layers. Multicellular hairs called as trichomes are present on both the layers. Stomata occur only in the lower epidermis. This condition is described as hypostomatic. 

Mesophyll is the ground tissue that occurs between the two epidermal layers. It is exclusively composed of chlorenchyma cells. The mesophyll is characteristically differentiated into two regions, namely an upper palisade parenchyma and a lower spongy parenchyma. Thus, option B is correct.

Mark out the incorrect statements.


A) Bulliform cells are found on adaxial epidermis of grasses.
B) All vascular bundles have different size in leaf showing parallel venation.
C) Endodermis, pericycle, vascular bundle and pith constitute the stele.
D) Bastfibresare absent in primary phloem.

  1. B only

  2. D only

  3. A & B only

  4. B & C only


Correct Option: A
Explanation:

Generally, the patterns of the leaf veins, or vascular bundles are pinnate and the veins are free; that is, they all diverge and never coalesce, either along their sides or at the ends. So, the incorrect statement is all vascular bundles have different size in leaf showing parallel venation.

One of the following is absent in the phloem of mostly monocots.

  1. Sieve tubes

  2. Phloem parenchyma

  3. Companion cells

  4. Phloem fibres


Correct Option: A

Match the columns.

A) Syntheticauxin  i) Zeatin 
B) Natural cytokinin from coconut milk  ii) IBA
C) naturalauxin  iii) Kinetin 
D) purine from herring sperm DNA iv) NAA
  1. $A-iv,B-i,C-ii,D-iii$

  2. $A-ii,B-i,C-iv,D-iii$

  3. $A-iv,B-iii,C-ii,D-i$

  4. $A-ii,B-iii,C-iv,D-i$


Correct Option: A
Explanation:
 A synthetic auxin (NAA) suppresses secondary wall cellulose synthesis and enhances elongation in cultured cotton. Zeatin is a cytokinin derived from adenine, which occurs in the form of a cis- and a trans-isomer and conjugate. Five naturally occurring (endogenous)auxins in plants include indole-3-acetic acid, 4-chloroindole-3-acetic acid, phenylacetic acid, indole-3-butyric acid, and indole-3-propionic acid. The mechanism of production of kinetin in DNA is thought to be via the production of furfural — an oxidative damage product of deoxyribose sugar in DNA — and its quenching by the adenine base's converting it into N6-furfuryladenine, kinetin. So the correct option is
 ' A−iv,B−i,C−ii,D−iii'.

The number of types of cells presents in the adaxial epidermis of grasses

  1. $1$

  2. $2$

  3. $3$

  4. $4$


Correct Option: A
Explanation:

The upper surface of the leaf is known as the adaxial surface. The type of cells presents in the adaxial epidermis of grasses is bulliform cells (only one type). These are large bubble-shaped cells present in the adaxial or upper surface of the leaves in monocots. So, the correct answer is '1'.

Select the true statement for a isobilateral leaf.

  1. The stomata are present on both the surfaces

  2. Mesophyll is differentiated into palisade & spongy

  3. Cuticle is always absent on both surfaces

  4. Vascular bundles are open & conjoint


Correct Option: A
Explanation:

Monocot leaves are called isobilateral leaves since both the sides of monocot leaves are more or less similar. Isobilateral leaves orient themselves parallel to the main axis and parallel to the direction of sunlight. Epidermis is single layered, present on both surfaces and has cuticles (cuticularized) and stomata on both surfaces (amphistomatic). It  is composed of compactly arranged oval or barrel shaped thin walled parenchymatous cells. Mesophyll is the ground tissue that is present between the two epidermal layers. Vascular bundles are of two types- small bundles are abundant and larger bundles are found in between them.

So the correct option is 'the stomata are present on both the surfaces'.

Cells which help in rolling and unrolling of leaf lamina in grasses are 

  1. Complementary cells

  2. Motor cells

  3. Passage cells

  4. Companion cells


Correct Option: B
Explanation:
  • The leaves of monocots have a large bubble-shaped epidermal cell called bulliform cells.
  • They are also known as motor cells.
  • They are present in the adaxial surface of the leaves.
  • They play an important role in the unfolding of the developing leaves and in the rolling and unrolling of mature leaves in response to the alternating wet and dry conditions.
  • So, the correct answer is 'Motor cells'.

In monocot leaves, the mesophyll Consists of

  1. Aerenchyma

  2. Only Spongy chlorenchyma

  3. Only Palisade Chlorenchyma

  4. Palisade and Spongy Chlorenchyma


Correct Option: B
Explanation:
Mesophyll in monocot leaves lie between the two layers of epidermis and is not differentiated in palisade and spongy tissues. Instead, the undifferentiated mesophyll is similar to spongy tissue. It consists of the mesophyll cells that are chlorenchymatous and contain a number of chloroplasts. 
So the correct answer is 'Only spongy chlorenchyma'.
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