1. Lecture on leaves by Dr Chanchal Kumar Biswas Department of Botany

2. Leaves
Leaves are green photosynthetic organs of the plant arising from the nodes or directly from stem. The leaves are usually flattened either bifacial i.e. dorsoventral or may be unifacial i.e. isobilateral.

3. Kinds of leaves:
Foliage leaves: These are most common leaves are developed from nodes, these leaves are concerned with the photosynthesis, and transpiration.
Scale leaves ( Cataphylls): these are thin scaly or membranous structure occur on under ground stem and branches. Morphologically these are the reduced form of foliage leaves. E.g Rhizome, corm etc.
Seed leaves or cotyledonary leaves: these are the leaves of embryo forming a the 1st one or two leaves during seed germination.

4. Bract leaves : These are special leaves either modified in structure or colour or may be ordinary foliage leaves reduced in form and developed at the base of individual flower or the whole inflorescence.
Floral leaves and sporophylls: these are leaves of flower i.e. sepal, petal, parianth etc. are the floral leaves and spore bearing leaves are called sporophylls. Stamen and carpel are the sporophylls of Angiosperms.

5. Modification of leaves:
Leaf tendrils: here the whole leaves are modified in to a slender, coiled, thread like structure. Its helps the plant to upward movement. E.g. Pisum sativum
Spine: in this case the leaves are metamorphosed in to a sharp pointed structure. It helps the plant to reduce transpiration as well as defensive organ. Opuntia dilenii

6. Phyllode: It is green flattened modified petiole of leaves
Phyllode: It is green flattened modified petiole of leaves. Here the leaves are fall very early or not develop and from the petiole the phyllode are developed. These leaves functions as ordinary leaves. Acacia auroculoformis
Fleshy leaves: these are the modification of normal leaves for storage of water and mucilage. These laves are also called as succulent leaves. Aloe barbadensis.

7. Hooks: some times the leaves are modified in to hooks
Hooks: some times the leaves are modified in to hooks. As in the case of Bignonia anguiscati the three terminal leaf let are modified in to sharp and hard hooks. It functions for upward movement of plants.
Root like structure: the submerged leaves of some plant are modified in to finely dissected root like structure. Myriophyllum indicum.
Pitcher plant: It is found in Nepenthes khasiana. In this plant the leaf become modified in to a pitcher filled up with a liquid containing digestive enzyme. The attractive colour of the pitcher attract the insect which fall inside the pitcher and digested and ultimalely absorbs by the inner wall of the pitcher.

8. Insectivorous plant other then pitcher plant
Sundew (Drosera sp) The leaf of the drosera is stalked, the lamina is rolled or folded to form a globular or flat like structure bearing numerous tentacles, which execute movement as a response to the touch by the insect. Simultaneously the insect are trapped by the tentacles and utilize by the plant.
Bladderwort: The bladders of the plants form the insect catching apparatus. It is a root less free floating herb. The bladder are born on the segment of submerged leaves which catch the insect. Urticularia stellaris ( Lentibulariaceae)

9. Aldrovendra: In Aldrovendra vesiculosa ( Droseraceae)
An aquatic herb the leaves are metamorphosed in to a insect trapping organ. The leaves has an expanded petiole, the lamina is divided in to two halves by a midrib which act as a hinge so that the two halves of the blade can be closed and open along the hinge like midrib. On the inner side and on the margin there are numerous bristle like out growth which are sensitive. When the insect come in contact the two halves are closed with insect.

10. Stipule
It is a out growth of hypopodium or leaf base which is a tiny structure growing on the both side of a leaf base or may be large and conspicuous or variously modified to discharge special function. These are following types.

11. Free lateral: These are tiny slender free outgrowth on both side of petiole at the base. Hibiscus rosa-sinensis
Adnate: These are lie attached with the petiole on the both side up to a certain height. Rosa sinensis. Rosaceae

12. Intrapetiolar: when stipule occurring on the both sides of opposite leaves unite together by their inner margin and placed in between the leaves and stem. Gardenia jasminiodes Rubiaceae
Interpetiolar: Here stipule lying between the petioles of two opposite leaves and the stipules unite together by their outer margin and appear on the stem at the node. Ixora sp Rubiaceae

13. Ochreate:
When stipule are sheath like and more or less tubular in structure and enclosing some portion of stem. In this case several stipule unite together and forming tubular structure. Polygonaceae Polygonum barbatum.

14. Modified stipule Foliaceous stipule:
When stipule are very large and conspicuous leaf like on the both side at the leaf base. Pisum sativum.
Tendrillar stipule:
When stipule become coily & slender tendrils which helps the plant for up ward movement. Smilex zeylanica Liliaceae

15. Spinous :
When stipule are modified into spine like structure called spinous stipule. Zizyphus mauritiana Rhamnaceae
Convolute or Bud scale: When stipule are modified in to membranous scale like structure and protect the buds by covering all round. Ficus benghalensis, Artocarpus heterophyllus, Hevea brasilensis.

16. Types of Leaves
Simple leaf: when leaf contain one and only one leaf blade or lamina called simple leaf. The margin of simple leaf may be entire or incised to any depth but never touch the midrib.
Compound leaf: A leaf is said to be compound when it contain more the one articulation and the leaf is broken in to a number of small segments called leaflet which are free from one another and arrange on the axis.

17. Shape of Leaf

18. Base of Leaf

19. Apex of leaf

20. Margine

21. Types of compound leaf :
Pinnately compound leaf: in this case the leaflet are arranged either alternately or in opposite manner on the both side of the rachis directly or on the branches of the rachis.
Theses are following four types.

22. Unipinnate:
When midrib or rachis bears the leaflet directly called unipinnate.
There are two types of unipinnate compound leaf.
-- Peripinnate: When rachis bears even number of leaflet i.e. leaflets are arranged in pairs. E.g. Cassia sp Tamarindus indica.
Imperipinnate:
when rachis bears odd number of leaflet i.e. rachis end by a terminal single leaflet. Clitoria ternate, Azadirachta indica

23. Bipinnate: In this case secondary branches are produced from the rachis which bears leaflets i.e. this leaf is twicely pinnate. Mimosa pudica, Acacia arabica.
Tripinnate: When rachis produces secondary branches which in turn again produce tertiary branches bearing leaflets i.e. the leaf is thricely pinnate. Moringa olifera Oroxylon sp (Bignoniaceae)

24. Decompound:
When leaf is pinnate by more then three times called decompound. E.g. Foeniculum vulgare Coriandrum sativa

25. Palmately compound leaf : When leaf does not have a rachis as such condition the leaflet arise from the top of the petiole. These are flowing types.
Unifoliate:
Bifoliate: When two leaflet are articulated at the apex of the petiole. Bignonia grandiflora Hardwickia binata. (Caesalpinaceae)
Trifoliate: When three leaflets are articulated at the apex of the petiole. E.g Vitex negundo, Oxalis corniculata

26. Quadrifolioate:
When four leaflets are articulated at the apex of the petiole. E.g. Marselia quadrifolia
Digitate or Multifoliate: When more then four leaflets are articulated to the apex at the apex of petiole. E.g. Bombax ceiba Gynandropsis gynandra (Capparidaceae)

27. PHYLLOTAXY It is the mode of arrangement of leaves on the stem and on the branches. These are mainly classified under three category.
1. Spiral or Alternate Phyllotaxy: Here each node bear only one leaf. The successive leaves usually form a spiral pattern all round the stem. So that all leaves are found to lie in a fixed number of vertical rows called orthostichies.
2. Opposite Phyllotaxy: In this type of Phyllotaxy two leaves are inserted at each node which are opposite to each other i.e. bearing pairs of leaves at each node.
3. Whorled Phyllotaxy: When three or more leaves are arranged at each node in a circle or round the stem i.e. they arranged in verticillate manner called whorled Phyllotaxy. Leucas sp, Nerium indicum,

28. The spiral type of phylotaxy are of following types.
A. Distichous: In this type the 3rd leaf base falls vertically above the 1stleaf base, 4th above the 2nd leaf base and so on. So there are only two orthostichies on which all leaves are present. E.g. Graminae.
B. Tristichous: In this case the 4th leaf base falls vertically on the 1st leaf base, 5th on the 2nd and so on. So there are only three orthostichies are present on which all leaves are present. E.g. Cyperaceae.

29. C. Pentastichous: In this case the 6th leaf base falls vertically on the 1st leaf base, 7th on the 2nd, 8th on the 3rd and so on. So there are five orthostichies are present on which all leaves are placed. Hibiscus roar-sinensis, Ficus benghalensis.
D. Octastichous: here the 9th leaf base falls vertically above the 1st leaf base, 10th above the 2nd leaf base, 11th above the 3rd leaf base and so on. Here altogether eight orthostichies are present on which all leaves are present. E.g Carica papaya.

30. E. Parastichous: When the number of orthostichies are not possible to count. So all leaves are placed on indefinite number of vertical line. Phoenix sp
Angular divergence:
The distance formed upon the spiral of the stem between the successive leaves is called divergence. The angle subtended by the divergence at the centre is called angular divergence.
Angular divergence= No of circle or circles/ no of leaves or orthostichies

32. Opposite Phyllotaxy: In this type of Phyllotaxy two leaves are inserted at each node which are opposite to each other. These are two types.
Opposite Decussate:
When pair of opposite leaves of one node stands at right angle to the next upper and lower pair of leaves. E.g. Calotropis procera, Ocimum sanctum.
Opposite Superposed:
When opposite pairs of leaves are arranged in one plane i.e. it placed in parallel fashion. Quisqualis indica Malpighiaceae. Psidium guajava Myrtaceae.

33. 3. Whorled Phyllotaxy:
When three or more leaves are arranged at each node in a circle or round the stem i.e. they arranged in verticillate manner called whorled Phyllotaxy. Leucas sp, Nerium indicum,