Leaf Structure

leaf modifications and adaptations

1. LEAF Structure , Adaptions and Development Kamaljit Sidhu Associate professor Deptt . Of Botany KCW , Civil Lines Ludhiana

2. LEAF

3. Characteristics of Leaf Leaf is an exogenous lateral outgrowth It develops from the shoot meristems of leaf primordia It has limited growth as the i ntercalary meristem from which it develops is consumed in growth Borne at the node of the stem Bears an axillary bud in its axil Green in colour due to photosynthesis Apical bud absent in the leaf

4. Functions of leaf Two types of leaf functions- Primary and Secondary Primary functions are Photosynthesis, gaseous exchange Transpiration , conduction of water , protection of buds Secondary Functions- Storage of water in succulents , food in leaf base of Onion , air for buoyancy in aquatic plants , reproduction in developing buds- Bryophyllum Nitrogen fixation- by leaf nodules- Ardisia Modifications – for climbing-tendrils , spines, hooks, plants, for support, catching insects in insectivorous plants protection of buds , attracting insects for pollination- Poinsettia Reducing transpiration-spines or phyllodes , form pitchers to store water Modified to form floral parts for sexual reproduction Floatation in Salvinia,Eichornia

5. Secondary functions of the Leaf Mucilage storage-succulents Food storage-Onion Air storage-Hydrophytes Leaf buds-Reproduction Leaf nodules- Ardisia Pollination-Poinsettia

6. PARTS OF A LEAF A typical foliage leaf consists of three parts: Leaf base , petiole and Lamina Lamina or leaf blade( Epipodium )- Thin ,expanded , green part of the leaf to perform photosynthesis Flattened lamina supported by veins and veinlets Contain vascular tissues for the conduction of water and minerals and food Two faces of lamina- Adaxial -ventral or upper surface Abaxial -Dorsal or lower surface Leaves with two surfaces distinct- Dorsiventral leaves Leaves with similar surfaces- isobilateral (in monocots) Petiole( mesopodium )- Cylindrical or sub cylindrical stalk of the leaf, lifts the lamina above the surface of the stem to provide maximum exposure Leaf with a petiole- petiolate , without a petiole- sessile Peltate leaves -petiole attached to the centre of the lower surface of the lamina , placed at right angles to the petiole- Lotus Winged petiole- Lemon

7. PARTS OF A LEAF

8. PARTS OF A LEAF Petiolate leaf Sessile leaf Peltate leaf Phyllode

9. PARTS OF A LEAF Leaf base( hypopodium or vagina)- Part of leaf joined to the node, indistinguishable from the petiole Protects the young bud in the axil, in legumes swollen Responsible for sleep and shock movements in Mimosa pudica Pulvinus -Swollen leaf base S heathing leaf base- Leaf base swollen broadened to enclose the stem Sheathing leaf base two types- Amplexicaul and Semi- amplexicaul Amplexicaul -Enclosing the stem completely-Grasses Semi- amplexicaul - Enclosing the stem partially-Buttercup Stipules- Leaf with lateral outgrowths-Stipules Stipulate- Leaf with stipules-Stipulate Exstipulate- Leaf without stipules-Exstipulate Ligule- Tongue shaped outgrowth present between leaf base and lamina Ligulate- Leaf with a ligule

10. PARTS OF A LEAF Pulvinus Amplexicaul leaf base Semi- amplexicaul leaf base

11. PARTS OF A LEAF Stipules- Lateral outgrowths of the leaf base Types of Stipules Free Lateral- Small , free green outgrowths- Hibiscus Scaly- Small, membranous stipules- Cassia fistula Axillary- Fused to the innermost margins to become axillary -Gardenia Opposite -Fused from their outer margins to become opposite the leaf- Castor Interpetiolar -Adjacent stipules of the opposite leaves are fused to appear in petioles- Ixora Adnate - Stipules fused with the petioles to a distance so that the leaf base looks to be winged- Rose Ochreate -Stipules fused to form a sheath or ochrea around the stem- Rumex Convolute- Stipules of young leaves are connate and protect the bud ,fall as soon as the leaf unfolds- Ficus Foliaceous - Large and green- Pisum Stipular spines -Stipules transformed into spines- Acacia Stipular Tendrils- Stipules are modified into chord like tendrils- Smilax

12. Types Of Stipules

13. Types of leaves Foliage leaves- These are common green leaves for photosynthesis Scale leaves(Cataphylls )-Non green ,sessile, membranous structures Bracts( Hypsophylls )- S pecialised leaves which bear flowers in their axil Bracteoles- Two small leaf like structures, found attached to the stalk of the flower Prophylls - First one or two leaves of a branch which differ from the other leaves Floral leaves- Special leaves which represent the vegetative parts of the leaf Sporophylls - Modified spore bearing leaves of the flower

14. Types of leaves Foliage leaf Scale leaf Bracts Bracteoles

15. Venation

16. Reticulate Venation The veinlets form a network Found in dicots 2types-Pinnate or unicostate reticulate venation,Palmate or multicostate reticulate Unicostate reticulate venation- Lamina has s single p rincipal midrib extending from base to apex – Peepal Multicostate reticulate venation- Number of prominent midrib which extend from base to apex-2 types Convergent- Principal veins converde towards the apex of the lamina- Zizyphus Divergent- Principal veins diverge towards the margins- Castor

17. Types of Reticulate Venation

18. Parallel Venation Veins are inconspicuous ,veins run parallel to each other Characteristic of monocots exceptions- Smilax,Colocasia 2 types- Unicostate parallel venation, Multicostate parallel venation Unicostate parallel venation-Single principal midrib runs to of lamina-Banana Palmate or Multicostate parallel-Several parallel arise from base of the lamina 2 types- Convergent,Divergent Convergent-The principal veins converge towards the apex-Bamboo Divergent-The principal veins proceed toward the margins-Fan palm

19. Types of Parallel Venation

20. Furcate Venation

21. Phyllotaxy Of Leaves

22. Types OF Phyllotaxy

23. Types Of Cyclic Phyllotaxy

24. Alternate or spiral P hyllotaxy A single leaf arises at each node and the leaves of the adjacent node lie the opposite sides Spiral arrangement Appear to be arranged in vertical rows Also called as Orthostichy

25. Schimper -Brown Series or Fibonacci series A single leaf arises at each node and the leaves of adjacent nodes lie on opposite sides Arranged spirally on the stem and appear to be in vertical rows Two vertical rows-1/2 distichous 3 rows-1/3 - tristichous 5 rows-1/2+1/3=2/5 pentastichous Number in numerator and denominator of each fraction is the sum of two preceding ones- Fibonacci series or schimper brown series

26. Distichous in Vanda Tristichous in Cyperus

27. Phyllotaxy Phyllotaxy =Number of circle _________________ Number of leaves

28. Angle of Divergence The angle formed between two successive leaves and the centre of the stem is called angular divergence Phyllotaxy ×360°=angle of divergence In distichichous =1/2 × 360° In tristichous =1/3 × 360°

29. Whorled Phyllotaxy

30. Leaf Mosiac Present in sciophytes Leaves arranged in close spiral Young leaves fit like a mosaic in the interspaces Example- Acalypha

31. Leaf Incision Incision is the cutting or notching of lamina The pattern depends on the type of venation Pinnate -In a reticulated venated , simple leaf Cutting from margins towards the mid-rib Palmate- Occurs in multicostate , reticulate venated , simple leaf Cutting of lamina from the margins towards the base Types of incisions-Reaching up to half- fid, more than half- partite , near the base of the midrib- sect

32. Leaf Incision

33. Leaf Incision

34. Leaf Incision

35. Compound Leaves

36. Palmate Compound Leaves

37. Leaf Base

38. Petiole(Leaf Stalk)

39. Petiole(Leaf Stalk)

40. Shape of Lamina

41. Leaf Margins

42. Leaf Apex

43. Leaf Modifications

44. Nature of Tendrils Whole leaf tendrils Leaflet tendrils Petiolar tendrils Rachis and petiolar tendrils Rachis tip tendrils Leaf tip tendrils Stipular tendrils

45. Nature of Tendrils Whole leaf Tendril Leaflet Tendril Petiolar Tendril Rachis and petiolar Tendril

46. Nature of Tendrils Leaf tip Tendril Rachis tip Tendril Stipular Tendril

47. Leaf Spines

48. Leaf Spines Opuntia Ulex Barberry

49. Leaf Modifications Leaflet hooks Phyllodes Leaf bladders Leaf Pitchers

50. Internal Structure of Dicot and Monocot leaf

51. Differences between Monocot and Dicot leaf

52. Internal Structure of a Dicot Leaf

53. Typical Monocot Leaf ( IsobilateralLeaf )