· Specialized organ of Photosynthesis in plants.
· The green leaves are termed as foilage leaves while non-green leaves are called cataphylls.
· The leaves with sporangia are called sporophyll.
· Leaves of the green plant are also called the kitchen of green plants as it carries out most of the vital activities like respiration, transpiration etc.
Various Parts of Leaf
· Leaf base – The lower part of the leaf, which is attached to the stem.
· Pulvinus – It is the swollen leaf base common in leguminous plants.
· Sheathing leaf base – leaf base is expanded and covers the stem partially or completely e.g, Gramineae, grass, sugarcane, wheat etc.
· Stipules – Lateral outgrowth from the leaf base of dicots. Stipules are absent in monocots.
· Leaf base – The lower part of the leaf, which is attached to the stem.
· Pulvinus – It is the swollen leaf base common in leguminous plants.
· Sheathing leaf base – leaf base is expanded and covers the stem partially or completely e.g, Gramineae, grass, sugarcane, wheat etc.
· Stipules – Lateral outgrowth from the leaf base of dicots. Stipules are absent in monocots.
· Lamina or leaf Blade
· It is the expanded green portion of the leaf.
· It has several thin veins and veinlets (smaller veins)
· Veins not only support but also conduct the water minerals and food through the leaf.
· It has two surfaces
· Adaxial (upper) towards the apex
· Abaxial (lower) away from the shoot tip.
· Petiole
· It is the stalk of the leaf by which leaf is attached to the stem
· Leaf having petiole – petiolate
· Leaf devoid of petiole – sessile
· Winged petiole in citrus
· Petiole is common in dicot but absents in monocot.
· It has several thin veins and veinlets (smaller veins)
· Veins not only support but also conduct the water minerals and food through the leaf.
· It has two surfaces
· Adaxial (upper) towards the apex
· Abaxial (lower) away from the shoot tip.
· Petiole
· It is the stalk of the leaf by which leaf is attached to the stem
· Leaf having petiole – petiolate
· Leaf devoid of petiole – sessile
· Winged petiole in citrus
· Petiole is common in dicot but absents in monocot.
Venation
· The arrangement of veins and veinlets in the Lamina.
· The arrangement of veins and veinlets in the Lamina.
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| Fig: Showing Different parts of Leaf |
Two types of Venation are:
A. Reticulate Venation
· Vein and veinlets form net-like structures. e.g. In all dicots except Calophyllum and Corymbium
A. Reticulate Venation
· Vein and veinlets form net-like structures. e.g. In all dicots except Calophyllum and Corymbium
2 Types of Reticulate Venation are:
a. Pinnate or Unicostate Reticulate venation.
· Single midrib with lateral veins that run from the centre towards the margin or apex of the leaf.
· Common type of venation. e.g. Mango, Peepal etc.
b. Palmate or Multicuastate venation
· Several more or less equally strong ribs, which arise from the tip of the petiole and proceeds upward and outward.
i. Divergent type– leaf possesses many strong veins that arise at the base of the leaf-blade and then diverge from one another towards the margin of the leaf, like the fingers from the palm. e.g. Plants belonging to Malvaceae (cotton family), Cucurbita
ii. Convergent type – The principle veins coverage towards the apex of the lamina. e.g. Zizyphus (bayar), Cinnamomum (tejpat)
a. Pinnate or Unicostate Reticulate venation.
· Single midrib with lateral veins that run from the centre towards the margin or apex of the leaf.
· Common type of venation. e.g. Mango, Peepal etc.
b. Palmate or Multicuastate venation
· Several more or less equally strong ribs, which arise from the tip of the petiole and proceeds upward and outward.
i. Divergent type– leaf possesses many strong veins that arise at the base of the leaf-blade and then diverge from one another towards the margin of the leaf, like the fingers from the palm. e.g. Plants belonging to Malvaceae (cotton family), Cucurbita
ii. Convergent type – The principle veins coverage towards the apex of the lamina. e.g. Zizyphus (bayar), Cinnamomum (tejpat)
B. Parallel Venation
· Veinlets are inconspicuous i.e. do not form reticulations.
· Veins and veinlets are arranged in parallel rows.
· Common in Monocots except Smilax, Discorea (Yam), Alocasia, Colocasia
Types of Parallel Venation are
a. Pinnate – leaf has a prominent mid-rib, and this gives off lateral veins, which runs parallel to each other towards the margin or apex of the leaf blade. e.g. Banana, Turmeric etc.
b. Palmate venation or multicostate parallel venation
1. Divergent – Fan palms
2. Convergent – Bamboo, grasses etc.
· Veinlets are inconspicuous i.e. do not form reticulations.
· Veins and veinlets are arranged in parallel rows.
· Common in Monocots except Smilax, Discorea (Yam), Alocasia, Colocasia
Types of Parallel Venation are
a. Pinnate – leaf has a prominent mid-rib, and this gives off lateral veins, which runs parallel to each other towards the margin or apex of the leaf blade. e.g. Banana, Turmeric etc.
b. Palmate venation or multicostate parallel venation
1. Divergent – Fan palms
2. Convergent – Bamboo, grasses etc.
C. Furcate venation
Dichotomously dividing vein and veinlets. e.g. Ferns (Adiantum)
Dichotomously dividing vein and veinlets. e.g. Ferns (Adiantum)
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| Fig: Showing Different kinds of Leaf venation |
Phyllotaxy
(Phyll – leaves, taxis – arrangement).
· It is the arrangement of leaves on the stem or its branches.
· The object of this arrangement is to avoid shading one another so that the leaves may get the maximum amount of sunlight to perform their normal functions.
3 Types of Arrangement are:
1. Alternate or spiral – When a single leaf arises at each node. E.g. Sunflower, grasses, mustard etc.
2. Opposite – When two leaves arise at each node standing opposite to each other.
2 Types of Opposite are:
a. Decussate: One pair of leaves is seen standing at a right angle to the next upper or lower pair. e.g. Ocimum (Tulsi), Calotropis
b. Superposed: A pair of leaves is seen to stand directly over the lower pair in the same plane. e.g. Guava.
3. Whorled or Verticillate
· When there are more than two leaves at each node and these are arranged in a circle or whorl. e.g. Olender (Nerium)
B. Compound – Leaf blade or lamina is divided into several parts of segments called leaflets.
2 types of Compound Leaf are:
A. Pinnately compound leaves
· The leaflets are attached to the midrib or rachis
· Leaflets are arranged laterally (alternate or opposite) to the midrib.
a. Unipinnate
· All the leaflets touch the midrib of the leaf.
· Peripinnate – leaflets are even in number. e.g. Cassia, fistula
· Imparipinnate– Upper leaflet is unpaired. e.g. Rose
b. Bipinnate – When the compound leaf is twice pinnate i.e., the mid-rib produces a secondary axis that bears the leaflets.
e.g. Acacia
c. Tripinnate – the leaf is thrice pinnate i.e. secondary axis produces the tertiary axes which bear the leaflets. e.g. Drumstick (Moringa)
d. Decompound – the leaf is more than thrice pinnate. e.g Coriander, Dhania, Carrot (Gaajar)
(Phyll – leaves, taxis – arrangement).
· It is the arrangement of leaves on the stem or its branches.
· The object of this arrangement is to avoid shading one another so that the leaves may get the maximum amount of sunlight to perform their normal functions.
3 Types of Arrangement are:
1. Alternate or spiral – When a single leaf arises at each node. E.g. Sunflower, grasses, mustard etc.
2. Opposite – When two leaves arise at each node standing opposite to each other.
2 Types of Opposite are:
a. Decussate: One pair of leaves is seen standing at a right angle to the next upper or lower pair. e.g. Ocimum (Tulsi), Calotropis
b. Superposed: A pair of leaves is seen to stand directly over the lower pair in the same plane. e.g. Guava.
3. Whorled or Verticillate
· When there are more than two leaves at each node and these are arranged in a circle or whorl. e.g. Olender (Nerium)
Various Types of Leaves
A. Simple leaf – A leaf having a single and undivided lamina e.g. MangoB. Compound – Leaf blade or lamina is divided into several parts of segments called leaflets.
2 types of Compound Leaf are:
A. Pinnately compound leaves
· The leaflets are attached to the midrib or rachis
· Leaflets are arranged laterally (alternate or opposite) to the midrib.
a. Unipinnate
· All the leaflets touch the midrib of the leaf.
· Peripinnate – leaflets are even in number. e.g. Cassia, fistula
· Imparipinnate– Upper leaflet is unpaired. e.g. Rose
b. Bipinnate – When the compound leaf is twice pinnate i.e., the mid-rib produces a secondary axis that bears the leaflets.
e.g. Acacia
c. Tripinnate – the leaf is thrice pinnate i.e. secondary axis produces the tertiary axes which bear the leaflets. e.g. Drumstick (Moringa)
d. Decompound – the leaf is more than thrice pinnate. e.g Coriander, Dhania, Carrot (Gaajar)
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| Fig: Showing simple and Compound leaf |
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| Fig: Showing Different Types of the compound leaf |
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| Fig: Showing Types of Pinnately compound Leaf |
B. Palmate Compound Leaf:
· Leaflets radiate from the end of the petiole
· The leaflets are joined at a common point and may look like the fingers of a palm. e.g Citrus
Types
a. Unifoloate – single leafier joined to a petiole. eg. citrus.
b. Bifoliate – Have two leaflets attached to the tip of the petiole. e.g. Balanites
c. Trifoliate – Have three leaflets joined to a petiole. e.g. Trigonella (methi), Aegle marmelos (Bel), Oxalis (Chariamilo), Butea monosperma - flame of forest (papilonaceae)
d. Quadrifoliate - Have 4 leaflets joined to a petiole. e.g. Marsilea
e. Multifoliate or digitate – Five or more leaflets present at the tip of the petiole. e.g. Bombax, Cleome
· Leaflets radiate from the end of the petiole
· The leaflets are joined at a common point and may look like the fingers of a palm. e.g Citrus
Types
a. Unifoloate – single leafier joined to a petiole. eg. citrus.
b. Bifoliate – Have two leaflets attached to the tip of the petiole. e.g. Balanites
c. Trifoliate – Have three leaflets joined to a petiole. e.g. Trigonella (methi), Aegle marmelos (Bel), Oxalis (Chariamilo), Butea monosperma - flame of forest (papilonaceae)
d. Quadrifoliate - Have 4 leaflets joined to a petiole. e.g. Marsilea
e. Multifoliate or digitate – Five or more leaflets present at the tip of the petiole. e.g. Bombax, Cleome
a. Caduceus – leaf falling down soon after appearance. E.g. Opuntia
b. Deciduous – leaf fall occurs simultaneously at the end of the growing season. E.g. Mulberry.
c. Persistent – Leaves live move that one season. E.g. pinus, mango
Various Modifications of Leaf
A. Leaf tendril
· Thread like sensitive structure, coiled around the support to help the plant in climbing. They are of the following types.
· Whole leaf tendrils. – e.g. Lathyrus aphaca (wild pea)
A. Leaf tendril
· Thread like sensitive structure, coiled around the support to help the plant in climbing. They are of the following types.
· Whole leaf tendrils. – e.g. Lathyrus aphaca (wild pea)
· Leaflet tendrils – e.g. Pisum sativum (Pea), Lathyrus odoratus (sweet pea)
· Leaf tip tendrils – Gloriosa superba (glory lily)
· Petiolar tendrils – Nepenthes.
· Stipular tendril – Smilax (kukurdaino)
· Leaf tip tendrils – Gloriosa superba (glory lily)
· Petiolar tendrils – Nepenthes.
· Stipular tendril – Smilax (kukurdaino)
B. Leaf Spine
· Leaf modify into the spine in some plants to protect themselves from grazing animals and excessive transpiration.
· Whole leaf-spine – Opuntia
· Stipular spine – Zizyphus, Acacia
· Marginal Spine - Argimone (Margin of leaf-spine)
· Apex, as well as margin both, are modified into the spine in Aloe.
· Leaf modify into the spine in some plants to protect themselves from grazing animals and excessive transpiration.
· Whole leaf-spine – Opuntia
· Stipular spine – Zizyphus, Acacia
· Marginal Spine - Argimone (Margin of leaf-spine)
· Apex, as well as margin both, are modified into the spine in Aloe.
Pitcher Shaped Leaves
· Pitchers in the pitcher plant Nepenthes are modified leaves.
· The flattened leaf-like structure is leaf base.
· The long, coiled tendril-like structure is the petiole and the actual pitcher is a modified lamina or leaf blade.
· The function of pitchers is to capture and digest insects.
· The lid arises as an outgrowth of leaf apex.
· Pitcher plant grows in nitrogen-deficient soil.
· Bladderwort (Utricularia) is an aquatic carnivorous plant seen free-floating in tanks.
· Succulent leaves – The leaves are green fleshy, which store water or food materials. e.g. Aloe, Agave, Americana, Bryophyllum
· Scale leaf – Thin membranous other than green leaves (brown or white) found in Ruscus and Casuarinas.
· Pitchers in the pitcher plant Nepenthes are modified leaves.
· The flattened leaf-like structure is leaf base.
· The long, coiled tendril-like structure is the petiole and the actual pitcher is a modified lamina or leaf blade.
· The function of pitchers is to capture and digest insects.
· The lid arises as an outgrowth of leaf apex.
· Pitcher plant grows in nitrogen-deficient soil.
· Bladderwort (Utricularia) is an aquatic carnivorous plant seen free-floating in tanks.
· Succulent leaves – The leaves are green fleshy, which store water or food materials. e.g. Aloe, Agave, Americana, Bryophyllum
· Scale leaf – Thin membranous other than green leaves (brown or white) found in Ruscus and Casuarinas.
· Colored leaf – In Euphorbia pulcherrima (Lalupate), leaves are brightly coloured to attract insects for pollination.
Phyllode
· Modification of leafy petiole
· The petiole or any part of the rachis becomes flattened or winged taking the shape of the leaf and turning green in colour. This flattened or winged petiole or rachis is known as a phyllode. e.g. Acacia.
· Spines are modified leaf
· Thorns are the modified axillary buds or vegetative buds or stems.
· Ptyxis-The way in which a leaf is folded in bud condition is called ptyxis.
· Vernation-The manner in which leaves are arranged in the bud with respect to each other
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| Fig: Phylloclade |
High Yeilding Points from LEAF
1. Prefoliation: Arrangement of immature or young leaves in bud.
Types:
i. Ptyxis: Folding of the lamina in the bud
ii. Vernation: Arrangement of leaves in a bud with respect to each other
Types:
i. Ptyxis: Folding of the lamina in the bud
ii. Vernation: Arrangement of leaves in a bud with respect to each other
2. Pinnately compound leaf:
i. Unipinnate:
iii. Tripinnate: Moringa
iv. Decompound: Coriander, Carrot
i. Unipinnate:
- a. Peripinnate: Cicer, Tamarindus
- b. Imparipinnate: Rose
iii. Tripinnate: Moringa
iv. Decompound: Coriander, Carrot
3. Palmately compound leaf:
i. unifoliate: Citrus
ii. Bifoliate: Begonia
iii. Trifoliate: Oxalis, Agela
iv. Quadrifoliate: Marsilea
4. Heterophily: Presence of More than Two types of leaves in plant: Artocarpus, Eucalyptus
Anisophily: Condition in which two types of leaves are found at each node
5. Leaf Insertion:
i. Radical: Leaf arise from the reduced stem, generally from the underground level, e.g: Raddish, Carrot etc
ii. Cauline: Leaf arising from the Mainstem. eg: Maize
iii. Ramal: Leaf arising from the branches: Zizyphus
Also, Read Notes of other Lesson of Botany: