_stem

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LONG ANSWER QUESTION

1. Describe various types of aerial stem modifications.
Ans:
a) Tendrils b) Thorns
c) Hooks d) Phylloclade
e) Tuberous stem f) Bulbil

a) Tendrils: Wiry, coiled, sensitive structures produced by weak stemmed plants are
called tendrils.
Eg:- Terminal bud is modified into tendil in Vitis, axillary bud is modified in to
tendril in Passiflora.

b) Thorns: Hard, woody, pointed structures developed from Terminal /Axilary bud is
called thorn. They give protection.
Eg:- In Bougainvillea, Durantaand Punica– axillary bud is modified into thorns.
In Carissa terminal bud is modified in to pair of thorns.

c) Hooks: Woody curved sensitive structure formed from Axillary/ Terminal bud is
called Hook. They help in climbing.
In Hugonia axillary bud is modified into hook.
In Artabotrys apical bud is modified into an inflorescence peduncle into a hook.



d) Phylloclade: In xerophytes the leaves are modified into scales/spines to reduce
transpiration. The main stem is modified in to flattened structure to perform
photosynthesis. These are called phylloclades.
Eg: A) Opunita B) Cocoloba C) Casuarina.

In Opuntia, all the leaves of axillary bud are modified into spines and small hair like spines
called bards. These together called Areole.

Cladophyll / cladode is a variation of phylloclade. It may have one / more internodes that are
flat / cylindrical.
Ex: Asparagus, Ruscus.



e) Tuberous stem: The aerial stems which store food materials and become tuberous are
called tuberous stems.
Eg: Brassica oleraceavar, ganyloides (knoll Kohl), Bulbophyllum
In Bulbophyllum, generally one internode of the stem stores food and water and
becomes tuberous. It appears as a bulb like structure and is called pseudobulb, Due to
this adaptation; the plants can survive during unfavorable conditions.

f) Bulbils: In some plant species the vegetative and floral buds are modified into
condensed branches. They store food materials. These modified buds are called
bulbils. They help in vegetative propagation.
Ex: Dioscorea – Bulbils present in the axils of leaves.
Agave Globba– Bulbils present in the axils of bracts

Oxalis - Bulbils present at the top of tuberous root.

2. Describe various types of sub-aerial stem modifications?
Ans: In some weak stemmed plants the stem remains partly underground. These
stems are called sub-aerial stems. These are four types:
a) Runners b) Stolons
c) Suckers d) Offsets

a) Runners: In some weak stemmed plants the stem creeps on the soil and adventitious
roots develop at every node. Whenever internodes break off, nodes lead an
independent life.
Ex: Oxalis, Hydrocotyl vulgaris, Lippianodiflora



b) Stolons: In some plants the basal branches of the stem grow obliquely downwards
and touch the soil. There they produce adventitious roots. These branches are called
stolon. They help in vegetative propagation when they are separated from mother
plant, they live as independent plants.
Ex: Jasminum, Nerium.

c) Suckers: In some plants a part of the stem is underground. The underground branches
grow obliquely upwards from the axillary buds of nodes present below the soil. These
branches produce roots on the lower surface are called suckers.
Ex: Chrysanthemum, Mentha.

d) Offset:These are found in free floating water plants. The stem is reduced to a disc like
structure. Many leaves are developed from this stem in rosette manner. The axillary
buds of these leaves develop into short, slender branches of usually one internodal
length and grow horizontally above the water. These branches are called offsets.
When these offsets break-off they develop into new plants.



Ex: Pistia, Eiachhornia.

3. What are multipurpose stem modifications (or) Describe underground stem
modifications.
A) 1. The underground stems store food.
2. They help in vegetative propagation.
3. They are protected from herbivorous animals.
4. They act as organs of perennation. As they perform all these above characters they
are called multipurpose stem modifications. They are of following types.
1) Rhizome 2) Corm
3) Stem tuber 4) Bulb

a) Rhizome: It is an underground stem which grows horizontally below the soil It
contains nodes and internodes. Scale leaves are present at the nodes. It is
dorsiventrally differentiated and produces aerial branches as well as reproductive
organs from the dorsal side and adventitious roots from the ventral side. The branches
developed from the axillary buds not only store food materials but maintain horizontal
growth of the rhizome. Terminal bud develops and produces aerial branches. The
underground rhizome remains alive even in drought conditions.

Ex:- Zingiberofficinalis, Curcuma longa, Musa paradisiaca and Canna indica.



b) Corm: It grows vertically in soil. It bears nodes, internodes and scale leaves.
Axillaary buds produce daughter corms. Terminal bud is big and produce aerial
shoot.

Ex: Colocasia, Amorphophallus.

In Amorphophallus, special adventitious roots called pull roots keep the corm
at a particular depth in soil.

c) Stem tuber: The apices of underground branches that store food and become
tuberous are called stem tubers. The stem tuber is covered by brown periderm. It
bears many eyes that represent nodes. Each eye contains semi lunar leaf scar and an
axillary bud in its axil. Eyes help in vegetative propagation.
Plant name Reserve food
Helianthus tuberosus inulin
Stachystubifera Stachyose

Solanumtuberosum Starch

d) Bulb: It is special underground stem modification that does not store food materials
in stem. The stem is reduced to a biconvex shaped disc like structure. It bears
adventitious roots on its lower side and leaves on upper side. Leaf bases (scale leaves)
store food and water. Axillary buds produce daughter bulbs and terminal bud present
at the centre of the bulb develops into an aerial shoot producing inflorescence.

It is two types:



a) Tunicated bulb: The entire bulb is covered by dry membraneous scale leaves called
tunic. The fleshy leaf bases overlap one above the other in concentric circles.
Eg: Allium cepa.

b) Scaly/ imbricate/ naked bulb: Fleshy scale leaves are arranged loosely and tunic is
absent.
Ex: Liliumcandidum.
In Allium sativum a number of fleshy scale leaves called cloves are arranged as in
scaly bulb but a group of such cloves are enclosed in a whitish, skinny tunic.

SHORT ANSWER QUESTIONS

1. Define phylloclade. Describe it.
A) 1. The modified green, leaf like aerial stem that performs photosynthesis is called a
phylloclade.
2. It is a special modification of aerial stem that performs photosynthesis.
3. It is seen in xerophytes only.
4. The leaves are modified into scales / spines.
5. The phylloclades of casuarina are needle like in cocoloba are ribbon like and in
opuntia are flattened.
Eg: Opuntia, Casuarina and Cocoloba.



6. In Opuntia all the leaves of axillary bud are modified into a group of spines. A
group of spines and barbs is called areole. Each areole represents a node.

2. What is a stem tuber? How does it differ from tuberous stem?
A) 1. Swollen, tuberous bulged apex of the underground branch that store food materials
is called stem tubers. Ex: Solanum tuberosum.

Stem tuber Tuberous stem
1. It is an underground stem modification 1. It is an aerial stem modification
2. It does not possess roots.
3. It is brown in colour 2. It possess roots
4. It possess eyes 3. It is usually green in colour
4. It doesn’t posses eyes
Eg: Solanum tuberosum
Eg: Knol - kohl

3. What is a bulb? Describe various types of bulbs.
A) Bulb:
1. Special underground stem modification, that does not store food material in the stem
is called bulb.
2. The stem is reduced to a biconvex shaped disc like structure.
3. It bears adventitious roots on its lower side and leaves on upper side.



4. Leaf bases are scale leaves store food, water and become flesh.
5. Axillary buds produce daughter bulbs and terminal bud develops into an aerial shoot
producing inflorescence.
It is two types:
a) Tunicated bulb: The entire bulb is covered by dry membranous scale leaves called
tunic. The fleshy leaf bases overlap one above the other in concentric circles.
Eg: Allium cepa.
b) Scaly/ imbricate/ naked bulb: Fleshy scale leaves are arranged loosely and tunic is
absent.
Ex: Liliumcandidum.
In Allium sativum a number of fleshy scale leaves called cloves are arranged as in
scaly bulb but a group of such cloves are enclosed in a whitish, skinny tunic.

4. Differentiate rhizome and corm.
A)
Rhizome Corm
1. It grows horizontally below the 1. It grows vertically below the
soil. soil
2. It is dorsiventrally differentiated 2. It is not dorsiventrally
3. Apical bud is small. differentiated.
4. Contractile roots or pull roots 3. Apical bud is large
are absent. 4. Pull roots/contractile are
present.
Eg: Ginger, Turmeric
Eg: Amorphophallus

5. Differentiate bulb and bulbil.
A)
Bulb Bulbil
1. It is underground stem 1. It is a aerial stem modification.
modification. Stem is reduced to It is a modified vegetative or floral
biconvex discoid structure. bud.
2. It does not store food materials 2. It stores food material.
in the stem. The food is stored in



leaf bases or scale leaves.
3. Daughter bulbs that develop
from the axillary buds grow into 3. Bulbils detached from the
new plants. parent plant develop into
4. It produces adventitious roots individual plants.
on the lower side of the stem. 4. It does not bear adventitious
roots still germination.
Eg: Allium, Lilium Eg: Dioscorea, Agave, Globba.

VERY SHORT ANSWER QUESTION
1. Which underground stem modification does not possess roots? Mention its
scientific name.
A) Stem tuber does not possess roots.
Eg. Solanumtuberosum, Helianthus tuberosus, Stachystubifera

2. Which aerial stem modification is concerned with vegetative propagation? Give
two examples.
A) Bulbils are concerned with vegetative propagation. Eg: Dioscorea, Agave.

3. What is a cladophyll? How does it differ from phylloclade?
A) Cladophyll is a variation of phylloclade. It is a short green cylindrical or flattened
branch of limited growth which develops from the node of the stem or branch in the
axil of scale leaf. Phylloclade is a leaf like modified stem, or branch and that performs
photosynthesis.

4. What are scale leaves? Mention the names of any two stem modifications in
which scale leaves are present.
A) The leaves which are reduced to small, colourless, dry membranous structures are
called scale leaves. These are present in rhizome and corm.

5. Define pseudobulb. Give an example.
A) Pseudobulb is a aerial stem modification which stores food and appears as a bulb like
structure called Pseudobulb.
Eg: Bulbophyllum.

6. In which forms is the food stored in the stem tubers of Helianthus tuberosus and
Stachystubifera?



A) In Helianthus tuberosus food is stores in the form of inulin, and Stachystubifera it is
stored in the form of stachyose.

7. Define contractile roots, mention their function.
A) Special modified, mechanical adventitious roots present in Amorphophallus are called
contractile roots. They help the corm to kept at a particular depth in the soil.

8. Write briefly about eye like structures present on stem tuber.
A) Stem tuber bears eye like structures. Each eye represents a node. Each eye possesses a
semi lunar leaf scar and an axillary bud in its axil They help in vegetative
propagation.
Eg.Solanumtuberosum.

9. Define areole. Give an example.
A) The group of barbs and spines present at every node of phylloclade of opuntia is
known as areole. Eg: Opunita.

10. What is the sub-aerial stem modification found in Pistia? Name any one
terrestrial plant having the same type of modification.
A) i) Offsets ii) Agave Americana

QUIZ TYPE QUESTIONS

1. What is the seedling material used for raising potato plants?
A) Potato tubers bear many eye like structures. These ‘eye’ like structures help in
vegetative propagation which are separated from the tuber and used as seeding
material for raising potato plants.

2. How are weak stemmed plants exposed to sunlight?
A) Weak stemmed plants exposed to sunlight with the help of climbing organs such as
tendrils and hooks.

3. Phylloclades are found in plants growing in desert areas. Why?



A) In desert plants leaves are modified into scale leaves and spines to minimize the rate
of transpiration. In such plants stem modified into green leaf like structure to perform
is called phylloclade.

4. In Bulbophyllum, the tuberous part is called pseudobulb. Why?
A) In Bulbophyllum one internode of the stem stores food and water and becomes
tuberous. It looks like bulb. So that tuberous part is called pseudobulb.

5. Name the modified stems having the following characters
a) Presence of adventitious roots at every node.
b) Formation of adventitious roots from any part of the stem when contacted with soil.
c) Initially underground but later becomes aerial.
d) One internodal long branches that give rise to daughter plants.
A) a) Runner b) Stolon
c) Sucker e) Offset

6. How are scale leaves helpful to the underground stems?
A) In underground stems scale leaves protect the axillary buds and help in the storage of
food and water.

Important Questions

Long Answer Questions
1. Describe various types of aerial modified stems
2. Write about underground modified stems.
Short Answer Questions
1. Differentiate bulb and bulbil
2. What is stem tuber? How it is differentiated from stem tuber?
Very short answer questions
1. Which underground stem modification does not possess roots? Mention its scientific
name.
2. What is cladophyll? How does it differ from Phylloclade?
3. Define contractile roots. Mention their function.
4. Define areole. Give an example.
5. In which form is the food stored in stem tubers of Helianthus tuberosus and
Stachystubifera.
6. What is the nature of tendrils in Passiflora, Vitis and Cissus.


_stem

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