Leaf Structure

Leaf Structure

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  LEAF Structure , Adaptionsand Development Kamaljit Sidhu Associate professor Deptt. Of Botany KCW , Civil
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  LEAF
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  Characteristics of Leaf •Leafis an exogenous lateral outgrowth •It develops from the shoot meristems of leaf primordia •It has limited growth as the intercalary 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
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  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
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  Secondary functions ofthe Leaf Mucilage storage- succulents Food storage-Onion Air storage- Hydrophytes Leaf buds- Reproduction Leaf nodules- Ardisia Pollination- Poinsettia
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  PARTS OF ALEAF • 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
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  PARTS OF ALEAF
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  PARTS OF ALEAF Petiolate leaf Sessile leaf Peltate leaf Phyllode
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  PARTS OF ALEAF • 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 • Sheathing 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
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  PARTS OF ALEAF Pulvinus Amplexicaul leaf base Semi-amplexicaul leaf base
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  PARTS OF ALEAF • 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
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  Types Of Stipules
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  Types of leaves •Foliage leaves-These are common green leaves for photosynthesis • Scale leaves(Cataphylls)-Non green ,sessile, membranous structures • Bracts(Hypsophylls)-Specialised 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
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  Types of leaves Foliageleaf Scale leaf Bracts Bracteoles
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  Venation
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  Reticulate Venation • Theveinlets form a network • Found in dicots • 2types-Pinnate or unicostate reticulate venation,Palmate or multicostate reticulate • Unicostate reticulate venation-Lamina has s single principal 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
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  Types of ReticulateVenation
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  Parallel Venation • Veinsare 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
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  Types of ParallelVenation
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  Furcate Venation
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  Phyllotaxy Of Leaves
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  Types OF Phyllotaxy Phyllotaxy AlternateCyclic Leaf Mosiac 3 Types
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  Types Of CyclicPhyllotaxy Cyclic Opposite Opposite decussate Opposite Superposed Whorled 3 0r more leaves
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  Alternate or spiralPhyllotaxy •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
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  Schimper-Brown Series orFibonacci 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
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  Distichous in VandaTristichous in Cyperus
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  Phyllotaxy •Phyllotaxy=Number of circle •_________________ • Number of leaves
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  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°
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  Whorled Phyllotaxy
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  Leaf Mosiac •Present insciophytes •Leaves arranged in close spiral •Young leaves fit like a mosaic in the interspaces
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  Leaf Incision •Incision isthe 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
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  Leaf Incision Leaf Incision Pinnate Palmate
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  Leaf Incision Pinnate Pinnatifid PinnatipartitePinnatisect
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  Leaf Incision Palmate Palmatifid PalmatipartitePalmatisect
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  Compound Leaves
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  Palmate Compound Leaves
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  Leaf Base
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  Petiole(Leaf Stalk)
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  Petiole(Leaf Stalk)
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  Shape of Lamina
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  Leaf Margins
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  Leaf Apex
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  Leaf Modifications
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  Nature of Tendrils •Wholeleaf tendrils •Leaflet tendrils •Petiolar tendrils •Rachis and petiolar tendrils •Rachis tip tendrils •Leaf tip tendrils •Stipular tendrils
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  Nature of Tendrils Wholeleaf Tendril Leaflet Tendril Petiolar Tendril Rachis and petiolar Tendril
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  Nature of Tendrils Leaftip TendrilRachis tip Tendril Stipular Tendril
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  Leaf Spines
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  Leaf Spines Opuntia UlexBarberry
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  Leaf Modifications Leaflet hooksPhyllodes Leaf bladders Leaf Pitchers
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  Internal Structure ofDicot and Monocot leaf
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  Differences between Monocotand Dicot leaf
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  Internal Structure ofa Dicot Leaf
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  Typical Monocot Leaf (IsobilateralLeaf)