Remix education
Agriculture B.S.C

A Study of Stem and Their Modifications

Exercise: 3A
Study of Stem and Their Modifications

Stem: It is the axis of a plant bearing leaves with buds in their axils. It is formed from the elongation of plumule of the seed.
 It is negatively geotropic,, positively phototropic and negatively hydrotropic
 It is generally green, with buds, nodes, iternodes, leaves, branches, flowers and fruits
Function:
 Supports branches, leaves, flowers and fruits
 Helps in conduction of water and food material through xylem and phloem
 Green stems synthesize food
 Store food in modified as well as normal structures
 Protects vegetative parts and helps in propagation

Different types of plants according to stem structure (Figure 3A.1):
Acaulescent: A plant which is stemless or without visible stem; onion, garlic
Arborescent: A plant almost tree-like with a short main trunk; Australian grass tree
Arboreous: A tree with well-developed trunk; mango, jackfruit
Culm: A jointed stem with distinct nodes and internodes; grasses and sedges

Plant types according to stem structure

Arborescent Scape/ Acaulescent Culm
Here are different types /Forms of stems according to habits, as below:
Erect (Strong) Weak (cannot stand erect)
1. Herb (Succulent stem): Low, 
soft or coarse plant with annual 
stems (Figure 3A.2)
Types according to structure
i. Scape/Acaulescent: Shoot in 
1. Creepers
Herbaceous, spreads over a large surface area 
with daughter plants from different generations; 
Cynodon dactylon, Ipomoea batatas, Hydrocotyle 
asiatica(Figure 3A.2)

reproductive season only, 
without visible stem; onion, 
garlic
ii. Creeper: Creeps over a large 
surface area for vegetative 
reproduction, roots arise at 
nodes; grasses, Strawberry,
Oxalis 
iii. Culm: Solid nodes and hollow 
internodes - grasses
Types according to duration of 
life 
i. Ephemerals (Lives for few 
weeks); Cannabis, Cardamine
ii. Annuals (Lives for one season 
in a year); rice, wheat
iii. Biennials/Biannuals (Lives for 
two years); parsley, fennel, 
hollyhocks
iv. Perennials (Lives for more than 
two years); banyan, fig
1. Trailers (Prostrate – trails over surface)
(Figure 3A.2)
i. Procumbents: Lie flat; Basella, Evolvulus,
Tribulus
ii. Decumbents: For some length grow 
horizontally then straighten up; Portulaca, 
Lindenbergia
iii. Diffuse: Profuse branches in all directions; 
Boerhaavia
3. Climbers (Climbs up support) (Figure 3A.3)
i. Twiners/Stem climbers: Weak stems twine 
around support through specific movement 
(nutation); Clitoria ternatea, Convolvulus, 
Mikania scandens, Asparagus sp., Dolichos 
sp., Phaseolus sp.
ii. Tendril climbers: Climbs through specialized 
structures called tendrils; Pisum sativum, 
Clematis sp., Gloriosa sp., Antigonon sp.
a. Leaf, Lathyrus
b. Stem apex or axillary branch, Vitis and 
Passiflora
c. Petiole, Clematis
d. Leaf tip, Gloriosa
e. Inflorescence axis, Antigonon
iii. Root climbers: Adventitious roots act as 
holdfast to climb support; Betel vine (Piper 
betle), Piper longum, Scindapus, Cuscuta
iv. Scrambler/Rambler/Struggling plants & 
Hook climbers: Grow over other bushes with 
help of prickles, hooks, but do not climb; Rose, 
Calamus (Cane), Lantana, Carissa, 
Bougainvillea
v. Adhesive climbers: The climbing organs have 
adhesive discs; Ampelopsis, Ficus repens
vi. Lianas: Perennial, grow deep forest; Bauhinia, 
Ficus, Tinospora
2.Woody herbs/Undershrubs
Structurally in between herbs 
and shrubs; Lilac
3. Shrubs: Larger than herbs, 
smaller than trees, much branching, 
bushy appearance, no main trunk, 
woody branches, perennial; Rose 
(Rosa), China – rose
4. Trees: Biggest plants, woody 
trunks, perennial, there are three 
types:
i. Caudex: No branch, columnar; 
Palm trees
ii. Excurrent: Indefinite acropetal 
branching; Pines, Casuarina, 
Polyalthia
iii. Deliquescent: Spreading 
branching habits, Banyan 
(Ficus, Mango (Mangifera)

Plant types according to habits

Herb Creeper
Procumbent Decumbent Twiner

Shrub 
Undershrub

Caudex Excurrent Deliquescent
Figure 3A.3 Different climbers
Tendril
Climbers
Hook 
climber
Root climber Adhesive climber 
Liana

Figure 3A.4 Stem branching types
Biparous cyme Trichasium Racemose branching
Uniparous scorpiod cyme Uniparous helicoids cyme

 Dichotomy Helicoid dichotomy Scorpioid dichotomy
Branching of stems: Branches develop from axillary buds (Figure 3A.4):
Lateral/Axillary (arise from lateral buds)
1.Racemose/Monopodial: Lateral buds arise acropetally, 
single axis, grows indefinitely; Polyalthia, Casuarina, 
Alstonia
Dichotomous: Typical 
branching of Cryptogams
1. Normal dichotomy: 
Apical cell/cells

2.Cymose: Apical bud lost with development, limited 
vertical growth, spreading type, Shorea Robusta
a.Uniparous cyme – One strong branch
i. Scorpioid cyme: Successive branches arise 
alternately at right and left, straighten up, forms false 
axis called pseudopodium; Vitis (Grapes)
ii. Helicoid cyme: Successive branches arise alternately 
at one side only, straighten up, forms pseudopodium; 
Saraca indica
b. Biparous cyme: Two strong branches, develops 
asymmetrical shoot – Dichasium, appear as dichotomy, 
hence named False Dichotomy; Plumeria acutifolia, 
Carissa carandas, Mirabilis jalapa
c. Multiparous cyme: More than two strong branches, 
develops asymmetrical shoot – Trichasium (Nerium 
odorum), polychasium (Croton sparciflorus)
bifurcate giving rise 
two apical branches; 
pteridophytes
2. Sympodial 
dichotomy: 
Sometimes after 
bifurcation one half 
grows and the other is 
suppressed. Here also 
two types are there: 
a. Scorpioid: alternate 
suppression on left or 
right branching; Male 
shield fern
 b. Helicoid: 
Suppression of cells of 
one side only; Pteris
Modification of stem: Some stems are modified to fulfil different physiological
functions as described below:
Underground modification
Purpose: Vegetative 
propagation, Perennation, 
storage (Figure 3A.5)
Sub-aerial modification 
Purpose: Vegetative 
propagation, Perennation
(Figure 3A.6)
Aerial modification
Purpose: Vegetative 
propagation, Perennation
(Figure 3A.7)
1.Rhizome: Fleshy and 
horizontal brown stem 
below soil, small nodes and 
internodes covered with 
scaly leaves; Ginger 
(Zinziber officinalis), 
Turmeric (Curcuma longa), 
Canna, Water lily, Banana 
(Musa)
 Rootstock: Special 
rhizome with vertical stem, 
Alocasia indica
2.Stem tuber: Swollen tips 
of underground branches 
under soil, axillary buds 
called eyes covered with 
scaly leaves; Potato 
(Solanum tuberosum) , 
1.Runner and sobole: 
Special branches of 
creepers carry buds, 
buds develop into 
daughter plant at a 
distance after internodes 
elongate horizontally, get 
fixed into soil through 
adventitious roots; 
Cynodon dactylon (Doob 
grass), Oxalis, 
Hydrocotyle asiatica
2. Stolon: Special runner, 
grow vertically then bend 
down to soil and develop 
roots; Mentha, Fragaria
(Wild strawberry), 
Jasmine; Method used 
1. Phylloclade/Cladophyll
: Green photosynthetic 
flattened/ rounded 
succulent stem, leaves 
feebly developed or 
modified into spines to 
reduce transpiration, a 
kind of desert 
adaptation; Opuntia, 
Casuarina, Euphorbia, 
Cactus
2. Cladode: Phylloclades 
with single internode; 
Asparagus, Ruscus
3. Thorn: Axillary bud 
modified into thin hard 
structures; 
Bougainvillea, Duranta,

Helianthus tuberosus
3.Bulb: Underground 
modified bud with reduced 
stem as disc, fleshy storage 
scale leaves, there are two 
types, as below, 
a. Tunicated:Scale leaves 
arranged concentrically, 
Onion 
b. Scaly/Imbricate: Scaly 
leaves arranged loosely, 
Garlic
4.Corm: Condensed vertical 
rootstock, large apical bud, 
spherical node and inter 
node; Colocasia, Alocasia, 
Amorphophallus, Saffron, 
Gladiolus, Colchicum
in layering of fruit tress
3. Sucker: Underground 
runner, branches develop 
obliquely from nodes
above the soil; Mentha 
arvensis, Pineapple, 
Chrysanthemum
4. Offset: Thicker and 
shorter runners of aquatic 
plants, nodes bear 
rossette of leaves, tuft of 
roots at base; Pistia, 
Eichhornia
Acacia, Carissa
4. Stem tendril: Spirally 
coiled modified buds of 
climbers; Passiflora, 
Vitis
5. Bulbils: A condensed , 
fleshy axillary flower 
buds; Dioscorea, 
Globba, Agave, Oxalis
6. Thalamus: Floral axis; 
all flowers
7. Pseudobulb: Fleshy, 
tuberous internodes;
Many orchids
8. Dwarf shoot/Spur/
Brachyplast: Special 
secondary stems bearing 
more foliage leaves than 
main stem with close 
internodes; Berberis, 
Many gymnosperms
Figure 3A.5 Underground modifications of stem
Rhizome
 Root stock
Stem tuber Corm

Tunicated bulb Imbricate bulb
Figure 3A.6 Sub aerial modifications of stem
 Runner Stolon Phylloclade
Suckers
Offset
Figure 3A.7 Aerial modifications of stem
Dwarf shoot 

 Cladode

Tendril Bulbil Thalamus
Thorn
Pseudobulb

Questions
1. Define:
i. Shoot system ii. Acaulescent iii. Arborescent iv. Arboreous v. Culm
2. Enlist different types of stem modifications with function and proper examples.
3. Write down the important functions of stem.
4. Differentiate between
a. Stem and root b. Culm and Caudex c. Strong and weak stems
d. Thorn and prickles e. Underground and aerial modification of stem
5. What are the main types of plants according to habit.
6. Draw neat and labeled diagram of angiospermic plant.

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