Morphology of Stem

1. MORPHOLOGY OF STEM
Dr.Reeshna.T.P
1ST Year PGD Scholar
Dept .Of Dravyaguna Vijnanam
VPSV AVC Kottakkal

2. INTRODUCTION
Morphe = Form , Logos =Study
Morphology is the branch of botany that deals
with the study of external structure of the plant
like roots ,stem ,leaves ,flowers , fruits , seeds
etc. and their modifications.
Body of flowering plant can be divided into root
system and shoot system
Root system – comprises the roots and its
branches.
Shoot system –comprises stem, leaves ,buds,
flowers and fruits.

3. STEM CHARACTERISTICS
Stem develops from the Plumule of the seed.
It is positively phototropic and negatively
geotropic.
It is distinguishable into nodes and internodes.
Nodes hold buds which can grow into leaves,
flowers, cones, branches etc.
Internodes are the space between nodes.
Stem lacks a terminal cap.
Stem may be aerial, sub aerial or under ground.
It may be herbaceous(green) or woody.
Its surface may be smooth,waxy,hairy or spiny.

4. STEM CHARACTERISTICS
Stem may be solid or fistular.
It may be cylindrical, angular or winged.
Stem is pentangular in cucurbitacea.
Quadrangular in Ocimum,and
most of Rubiaceae family.
Triangular in Cyperus.

5. STEM CHARACTERISTICS
 Winged stem
Eg:-Verbesina alternifolia

6. BUDS
 The growth of shoot system is accomplished by
buds.
 A bud may be vegetative or flowering.
 On the basis of their position the buds are classified
into 3 categories :-
1) Apical or Terminal bud : It is terminal in position and
responsible for the terminal growth of the plant.
2) Axillary bud : It lies on the node , in the axil of the
leaf and gives rise to a lateral branch.
3) Accessory Bud : It also lies on the node, slightly
away from the axil of a leaf. It gives rise to lateral
branches. It is of 2 types –
Lateral to axillary bud is known as Collateral bud.
Above axillary bud is known as Superimposed bud.

7. BUDS

8. BUDS
• Cauline: Adventitious buds arising on stem.
• Radical:Buds arising on roots.eg:-Ipomea.
• Foliar:Buds arising on leaves.eg:-Kalanchoe.

9. CLASSIFICATION OF STEM
 The stem may be erect or weak.
 The erect stems are of 3 types:
1.Herbs
2.Shrubs
3.Trees
 The weak stems are 4 types :
1.Creepers
2.Trailers
3.Twiner
4.Climber

10. CLASSIFICATION OF STEM
A) HERBS
• They have greenstem.
• Sub divided on the basis of their duration of
life cycle as under :
1.Annuals: They complete their life history in a
few months time
Eg:- Triticum(wheat)
2.Biennials: They complete their life cycle in
two years time
Eg:- Daucus carota
3.Perennials : They are evergreen herbs.
Eg:- Cynodon (doob)

11. CLASSIFICATION OF STEM
Annuals
Eg : Wheat
Biennials
Eg : Carrot
Perennials
Eg: Cynodon

12. CLASSIFICATION OF STEM
A)HERBS
SCAPE
 Some herbs produce a leafless stem
meant to bear the flowers only.This is
called a Scape.
 eg:- Alliam(onion)
 Such plants are often
described as acaulescent.

13. CLASSIFICATION OF STEM
B)SHRUBS
 They have a woody stem which branches
profusely from the very base.
 The stem never grows in thickness beyond
a certain limit.
 eg :- Ocimum(basil)

14. CLASSIFICATION OF STEM
C)TREES
 They have woody stem which branches
sparingly.
 On the basis of bud growth the trees have
been sub divided as under:
1)Caudex
2)Excurrent
3)Deliquescent

15. CLASSIFICATION OF STEM
1)CAUDEX :
 Here only the terminal bud functions and the
lateral buds remains dormant .
 The plant thus has only one terminal crown
of leaves.
 eg:- Coconut(Cocos nucifera)
palm etc.

16. CLASSIFICATION OF STEM
2)EXCURRENT
 Here the terminal bud is dominant over the
lateral buds.
 The branches grow almost in acropetal
order.Oldest at the base and youngest at the
apex.
 The tree appear cone shaped.
 Eg:- Polyalthea,Casuarina ,
Pines etc.

17. CLASSIFICATION OF STEM
3)DELIQUESCENT OR DECURRENT
 Here the terminal bud is lost and only the
lateral grow .
 eg , Banyan ,Mango, Rubber etc.

18. CLASSIFICATION OF STEM
 CULM
 A woody stem with solid nodes and hollow
internodes is called as culm .
eg:- Bamboo (Bambusa arundinacea).

19. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
A)CREEPERS
 They creep on the soil surface producing
roots at the nodes.
 They radiate in various directions from one
center.
 Thus they represent plants
of several generations.
Eg :- Cynodon

20. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
B)TRAILER
 The stem grows horizontally forward without
producing roots at the nodes.
 They are rooted in the soil at one point only.
 They are of 3 types:
1.Procumbent
2.Decumbent
3.Diffuse

21. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
B)TRAILER
1.Procumbent :
 The plant grows perfect horizontally along
the ground.
Eg:- Convolvulus, Basella, Alternanthera.

22. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
B)TRAILER
2.Decumbent :
 Here the plant grow horizontaly for some
distance and then rises upward.
Eg:- Lindenbergia

23. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
B)TRAILER
3)Diffuse:
 Here the branches spread upward in all
directions.
Eg:- Boerhavia diffusa

24. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
C)TWINER
 They climb through a support by coiling
around it .
eg :-Dioscorea,Dolichos,Ipomoea

25. CLASSIFICATION OF STEM
WEAK STEM CLASSIFICATION
D)Climber
 They climb through a support by the help
of specific structures .
They are of 4 types
1.Rootlet climbers : eg :-Piper betel , Cuscuta ,
Campsis
2.Hook Climber : eg:-Bougainvillea ,Artabotrys
3.Tendril Climber : eg:-Passiflora , Lathyrus
4.Adhesive disc climber : eg :-Ampelopsis

26. CLASSIFICATION OF STEM
D)Climber
1.Rootlet Climbers 2.Hook Climber
Piper betel

27. CLASSIFICATION OF STEM
D)Climber
3.Tendril Climber 4.Adhesive Disc Climber
Lathyrus Ampelopsis

28. CLASSIFICATION OF STEM
LIANA:
 A woody climber is called Liana.
eg:-Bougainvillea

29. CLASSIFICATION OF STEM
SCAMBLER:
A woody twiner is called Scambler.
Eg:- Calamus

30. BRANCHING
The branching is of 2 types
1)Lateral a)Racemose(Monopodial)
b)Cymose
2)Dichotomous(Apical)

31. BRANCHING
Racemose:-Lateral branches arise in acropetal
order.Plant becomes conical in shape.
Eg:-Polyalthia.
Cymose:-Growth of main apical bud is arrested
and a lateral bud just below the apex grows.
Eg:-Mango,Banyan.

32. BRANCHING
Cymose branching is
subdivided as
A)Uniparous:Growth of apical
bud is suppressed and only
one sub apical bud develops
at each branching. It is of 2
types
1)Helicoid:If successive lateral
branches develop on one
side. (Eg:- Terminalia)
2)Scorpoid:If successive
lateral branches arises on
either side alternately.(Eg:-
Cissus,Gossypium,Carissa)

33. BRANCHING
Cymose branching is subdivided as
B)Biparous:Growth of terminal bud is arrested
and 2 lateral bud develops at each branching.
Eg:-Mirabilous jalapa.
C)Multiparous:More than 2 lateral buds develop
at each branching.Eg:-Nerium
odoratum(Oleander),Euphorbia
tirucelli,Croton.

34. BRANCHING
Dichotomous:-When the apical meristem splits
into 2 branching.
Eg:-Lycopodium
Sympodial:-If half tip grows
normally and other half is
suppressed.
Sympoidal dichotomy may be
Helicoid or Scorpoid.

35. STEM MODIFICATIONS
STEM MODIFICATION
A)Underground B)SubAerial C)Aerial
1.Rhizome 1.Runner 1.Thorn
2.Corm 2.Sucker 2.Tendril
3.Bulb 3.Offset 3.Phylloclade
4.Tuber 4.Stolon 4.Cladode
5.Bulbil

36. STEM MODIFICATIONS
UNDERGROUND STEM MODIFICATIONS
1)RHIZOME:
 It grows horizontally forward under the soil
surface.
 It has distinct nodes and internodes with
scale leaves arising at the nodes.
 There are well marked apical and axillary
buds also.
eg:- Musa( plaintain), Zingiber(ginger),
Curcuma(turmeric ), ferns etc.

37. STEM MODIFICATIONS
UNDERGROUND STEM MODIFICATIONS
1)RHIZOME:
Musa( plaintain)
Zingiber(ginger)

38. STEM MODIFICATION
UNDERGROUND STEM MODIFICATIONS
2)CORM:
 It grows vertically upward in the soil.
 Like rhizome, they also possess distinct nodes
and internodes with scale leaves arising at the
nodes.
 In every season the apical bud ,after having
consumed the food of old corm , forms a new
corm over it.
eg :- Amorphophallus, Colocasia, Dioscorea,
Colchicum, Crocus, Ghadiolus.

39. STEM MODIFICATION
UNDERGROUND STEM MODIFICATIONS
2)CORM:
Eg:- Amorphophallus

40. STEM MODIFICATION
UNDEREGROUND MODIFICATIONS
3)BULB:
 It is characterised by having a discoid stem.
 The bulbs are of 2 type.
 1.Scaly or Imbricate and 2.Tunicate.
 The tunicate bulbs possess membranous scale
leaves called Tunics which are absent in Imbricate.
 In Tunicates fleshy bulbs are arranged in concentric
manner whereas in imbricate they are in spreading
manner .
 Tunicate bulb are seen in Allium cepa (onion), Tulipa,
Hyacinthus.
 Imbricate found in Lilium , Allium sativum (garlic).

41. STEM MODIFICATION
UNDEREGROUND MODIFICATIONS
3)BULB:
Tunicate Imbricate or Scaly
Allium cepa(onion) Allium sativum(garlic)

42. STEM MODIFICATION
UNDERGROUND STEM MODIFICATION
4)TUBER
 The tubers are almost globose structures
formed due to food storage at the tip of
stolon.
 The ‘eyes’ on potato tuber indicate the
position of nodes.
Eg:- Solonum tuberosum ( potato),
Helianthus tuberosus, Cyperus rotundus.

43. STEM MODIFICATION
UNDERGROUND STEM MODIFICATION
4)TUBER
Solonum tuberosum Cyperus rotundus

44. STEM MODIFICATION
SUB AERIAL MODIFICATION
1)RUNNERS:
 They grow horizontally forward creeping on
the ground and producing roots at the nodes.
Eg:- Cynodon ,Oxalis, Hydrocotyl.

45. STEM MODIFICATION
SUB AERIAL MODIFICATION
 SOBOLE
 An underground runner is called as sobole.
Eg:- Agropyron ,Saccharum spontaneum etc

46. STEM MODIFICATION
SUB AERIAL MODIFICATION
2)SUCKER :
 They grow obliquely upward from the
axillary bud of main stem producing
adventitious roots from their lower surface.
Eg:- Mentha (mint), Chrysanthemum etc

47. STEM MODIFICATION
SUB AERIAL STEM MODIFICATION
3)OFFSET :
 A thick and fleshy runner of aquatic plants
is called as offset
Eg:- Pistia, Eichhornia .

48. STEM MODIFICATION
SUB AERIAL STEM MODIFICATION
4)STOLON :
 Long slender branches arise from base of the
stem obliquely downwards which when
touches the soil produce adventitious roots.
 They have no specific direction of growth .
 Sometimes they change their
direction.
Eg:- Potato, Rubus,Jasminum

49. STEM MODIFICATION
AERIAL STEM MODIFICATION
1)Thorn
 In many plants the axillary bud is
modified into thorns.
 They may be unbranched -
eg:-Duranta, Principia, Citrus,
Aegle, Bougainvillea.
 Or branched -
eg:- Carissa,Flocourtia
 The thorns are different
from prickles as the latter
are simply emergences.

50. STEM MODIFICATION
AERIAL STEM MODIFICATION
1)Thorn
 branched -
eg:- Carissa,Flocourtia

51. STEM MODIFICATION
AERIAL STEM MODIFICATION
2)TENDRILS
 In some plants the axillary
bud is modified into tendrils.
Eg:- Passiflora.
 In some the terminal bud develop into tendrils.
 Eg:-Cissus quadrangularis,Vitis vinifera.
 The tendrils in Cucurbitaceae
represents fusion products
of leaf and its axillary branch.

52. STEM MODIFICATION
AERIAL STEM MODIFICATION
3)PHYLLOCLADE OR CLADOPHYLL
 Stem is flattened and functions as leaf.
Eg:- Opuntia , Muehlenbeckia, Ruscus , Lemna .
 In Opuntia the leaf base and the axillary shoot
fuses to form a structure called Tubercle.
 It is a raised up structure .
 The tubercles may unite to form the ribs.
Eg:- Mammillaria.
 The spine bearing area of the tubercle is called
as Areole

53. STEM MODIFICATION
AERIAL STEM MODIFICATION
3)PHYLLOCLADE OR CLADOPHYLL
Eg:- Opuntia, Mammillaria.

54. STEM MODIFICATION
AERIAL STEM MODIFICATION
4)CLADODE:
 Short, green, cylindrical or sometimes
flattened branches of limited growth.
 Developed from the node of stem or axile in
the scale leaves
 One internode long phylloclade is called as
cladode.
Eg:- Asparagus

55. STEM MODIFICATION
AERIAL STEM MODIFICATION
5)BULBIL:
 It is a condensed axillary bud
meant for vegetative
propogation.They store food
materials.
Eg:-In Dioscorea bulbifera bulbils
develop from axile of leaves.
 In Globba bulbifera they develop
in the axils of bracts on the
inflorescence.

56. Thank You