Stem.pptx

Morphology of Stem

1. MORPHOLOGY OF STEM Dr.Reeshna.T.P 1 ST 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 :- Apical or Terminal bud : It is terminal in position and responsible for the terminal growth of the plant. Axillary bud : It lies on the node , in the axil of the leaf and gives rise to a lateral branch. 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.

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