LeavesLeaves

By : Geonyzl Lepiten

LeafLeaf

Leaves Leaves provide trees provide trees with all their with all their food because food because they turn they turn sunlight into sunlight into food energy. food energy.

There are three main parts There are three main parts to a leaf: to a leaf:

The The basebase which is the which is the point at which the point at which the leaf is joined to the leaf is joined to the stem. stem. The The stalk or petiolestalk or petiole is is the thin section the thin section joining the joining the base to base to the laminathe lamina - it is - it is generally cylindrical generally cylindrical or semicircular in or semicircular in form. form. The The lamina or leaf lamina or leaf bladeblade is the wide part is the wide part of the leaf of the leaf

http://www.butler.edu/herbarium/treeid/treeparts.html

Compound leaf

Primary division of leaves (Primary division of leaves (types of leaf types of leaf configurationconfiguration))

Simple Compound

http://www.butler.edu/herbarium/treeid/treeparts.html

The leaf  blade has two The leaf  blade has two types of configurationtypes of configuration. It . It may be in one unitmay be in one unit, in which case the leaf is , in which case the leaf is called a called a simple leafsimple leaf, or , or it may be divided into it may be divided into numerous small parts that look like individual numerous small parts that look like individual leavesleaves and which form a and which form a compound leafcompound leaf. It may . It may be difficult to tell whether one is looking at a be difficult to tell whether one is looking at a simple leaf or the leaflet (pinna) of a compound simple leaf or the leaflet (pinna) of a compound leaf.  leaf.  The distinction can be made by the fact The distinction can be made by the fact that a leaf (simple or compound) has an that a leaf (simple or compound) has an axial axial budbud between the petiole and the stem between the petiole and the stem. .

Types of simple leavesTypes of simple leaves Are classified base on the following:Are classified base on the following: 1. leaf margin1. leaf margin 2. venation2. venation 3. leaf apex3. leaf apex 4. shape of the blade4. shape of the blade 5. leaf bases5. leaf bases 6. presence or absence of petiole6. presence or absence of petiole 7. leaf arrangement on the stem 7. leaf arrangement on the stem

(phyllotaxy)(phyllotaxy) 8. leaf surface8. leaf surface

(but of these may also used to classify the (but of these may also used to classify the compound leaves)compound leaves)

Classification by Leaf Arrangement on the Stem

Opposite: If each node has a pair of leaves 180 degrees apart.Alternate: Each node has a single leaf and the leaves of adjacent nodes point different directions

Whorled: If a node has three or more leaves attached.

rosetterosette is a circular is a circular arrangement of the arrangement of the leaves, with all the leaves, with all the leaves at a single leaves at a single height. Often, height. Often, perennial plants whose perennial plants whose foliage dies and the foliage dies and the remaining vegetation remaining vegetation protects the plant. protects the plant. Internodes are often Internodes are often shortened getting the shortened getting the leaves closer together, leaves closer together, as in lettuce and as in lettuce and dandelion. This is an dandelion. This is an example of a modified example of a modified stem. stem.

As a As a stemstem grows, leaves tend to appear grows, leaves tend to appear arranged around the stem in a way that arranged around the stem in a way that optimizes yield of light. In essence, leaves form optimizes yield of light. In essence, leaves form a helix pattern centred around the stem, either a helix pattern centred around the stem, either clockwise or counterclockwise, with (depending clockwise or counterclockwise, with (depending upon the species) the same angle of divergence. upon the species) the same angle of divergence. There is a regularity in these angles and they There is a regularity in these angles and they follow the numbers in a Fibonacci sequence: follow the numbers in a Fibonacci sequence: 1/2, 2/3, 3/5, 5/8, 8/13, 13/21, 21/34, 34/55, 1/2, 2/3, 3/5, 5/8, 8/13, 13/21, 21/34, 34/55, 55/89. This series tends to a limit of 360° x 55/89. This series tends to a limit of 360° x 34/89 = 137.52 or 137° 30', an angle known 34/89 = 137.52 or 137° 30', an angle known mathematically as the golden angle. In the mathematically as the golden angle. In the series, the numerator indicates the number of series, the numerator indicates the number of complete turns or "gyres" until a leaf arrives at complete turns or "gyres" until a leaf arrives at the initial position. The denominator indicates the initial position. The denominator indicates the number of leaves in the arrangement. the number of leaves in the arrangement.

This can be demonstrated by the This can be demonstrated by the following:following:

alternate leaves have an angle of 180° alternate leaves have an angle of 180° (or 1/2) (or 1/2)

120° (or 1/3) : three leaves in one 120° (or 1/3) : three leaves in one circle circle

144° (or 2/5) : five leaves in two gyres 144° (or 2/5) : five leaves in two gyres 135° (or 3/8) : eight leaves in three 135° (or 3/8) : eight leaves in three

gyres. gyres.

Leaf Shape Leaf Shape

BilobedBauhinia variegata

CordateIvy

Elliptical, ovalFicus pumila

LanceolateCodiaeum variegatum

LinearIris tectorum

Needle-shapedPinus massoniana

General shape

OblongFicus elastica

OvateHibiscus rosa-sinensis 

SagittateMikania micrantha

AuriculateArabis caucasica

oblanceolate Ilex glabra

spatulate Myrica pensylvanica

palmately lobed pinnately lobed scale-like awl-like

Venation (arrangement of Venation (arrangement of the veins)the veins)

There are two subtypes of venation, namely, There are two subtypes of venation, namely, craspedodromouscraspedodromous, where the major veins , where the major veins stretch up to the margin of the leaf, and stretch up to the margin of the leaf, and camptodromouscamptodromous, when major veins extend , when major veins extend close to the margin, but bend before they close to the margin, but bend before they intersect with the marginintersect with the margin

Feather-veined, reticulateFeather-veined, reticulate — the veins — the veins arise pinnately from a single mid-vein and arise pinnately from a single mid-vein and subdivide into veinlets. These, in turn, subdivide into veinlets. These, in turn, form a complicated network. This type of form a complicated network. This type of venation is typical for (but by no means venation is typical for (but by no means limited to) limited to) dicotyledonsdicotyledons. .

1. 1. Pinnate-netted, penniribbed, Pinnate-netted, penniribbed, penninervedpenninerved, penniveined; the leaf has , penniveined; the leaf has usually one main vein (called the mid-usually one main vein (called the mid-vein), with veinlets, smaller veins vein), with veinlets, smaller veins branching off laterally, usually somewhat branching off laterally, usually somewhat parallel to each other; parallel to each other;

eg eg MalusMalus (apples). (apples).

2.Palmate-netted, palmate-2.Palmate-netted, palmate-veined, fan-veinedveined, fan-veined; several main veins ; several main veins divergediverge from near the leaf base from near the leaf base where the petiole attaches, and where the petiole attaches, and radiate toward the edge of the leaf; radiate toward the edge of the leaf; e.g. most e.g. most AcerAcer (maples). (maples).

Palmate-veined leaf

Parallel-veined, parallel-ribbed, Parallel-veined, parallel-ribbed, parallel-nerved, penniparallelparallel-nerved, penniparallel — — veins run veins run parallelparallel for the length of for the length of the leaf, from the base to the apex. the leaf, from the base to the apex. Commissural veins (small veins) Commissural veins (small veins) connect the major parallel veins. connect the major parallel veins. Typical for most Typical for most monocotyledonsmonocotyledons, , such as such as grassesgrasses. .

By Brann on Flickr

Dichotomous — There are no Dichotomous — There are no dominant bundles, with the veins dominant bundles, with the veins forking regularly by pairs; found in forking regularly by pairs; found in GinkgoGinkgo and some and some pteridophytespteridophytes. .

By greenwoman46 on Flickr

Leaf marginsLeaf margins

The leaf margin is characteristic for a The leaf margin is characteristic for a genus and aids in determining the genus and aids in determining the species.species.

1. 1. entire:entire: even; with a smooth margin; even; with a smooth margin; without toothing without toothing

2. 2. ciliate:ciliate: fringed with hairs fringed with hairs

3. 3. crenate:crenate: wavy-toothed; dentate with wavy-toothed; dentate with rounded teeth, such as rounded teeth, such as FagusFagus (beech) (beech)

3. 3. dentatedentate: toothed, such as : toothed, such as CastaneaCastanea (chestnut) (chestnut)

a. coarse-toothed: with large teeth a. coarse-toothed: with large teeth

b. glandular toothed: with teeth that bear b. glandular toothed: with teeth that bear

glands. glands.

4. 4. denticulate:denticulate: finely toothed finely toothed

doubly toothed: each tooth bearing smaller doubly toothed: each tooth bearing smaller teeth, such as teeth, such as UlmusUlmus (elm) (elm)

5. 5. lobatelobate: indented, with the indentations not : indented, with the indentations not reaching to the center, such as many reaching to the center, such as many QuercusQuercus (oaks) (oaks)

6. 6. palmately lobedpalmately lobed: indented with the : indented with the indentations reaching to the center, such as indentations reaching to the center, such as HumulusHumulus (hop). (hop).

7. 7. serrate:serrate: saw-toothed with saw-toothed with asymmetrical teeth pointing asymmetrical teeth pointing forward, such as forward, such as UrticaUrtica (nettle) (nettle)

8. 8. serrulate:serrulate: finely serrate finely serrate

9. 9. sinuate:sinuate: with deep, wave-like with deep, wave-like indentations; coarsely crenate, such indentations; coarsely crenate, such as many as many RumexRumex (docks) (docks)

10. 10. spiny:spiny: with stiff, sharp points, with stiff, sharp points, such as some such as some IlexIlex (hollies) and (hollies) and CirsiumCirsium (thistles). (thistles).

Simple Leaves - Margin Structure

Types of compound Types of compound leaves:leaves:

Pinnately compoundPinnately compound – where the – where the leaflets are attached along the side leaflets are attached along the side of the stalk or rachisof the stalk or rachis

palmatepalmate - having the leaflets - having the leaflets arranged round a single point like arranged round a single point like fingers fingers

Other types of Other types of compound leavescompound leaves

Recognize specialized Recognize specialized leavesleaves

Shade LeavesShade Leaves- Leaves in the shade receive less - Leaves in the shade receive less

total light, thus tend to be thinner and total light, thus tend to be thinner and have fewer hairs than leaves on the have fewer hairs than leaves on the same tree exposed to direct light. same tree exposed to direct light.

Leaves of Arid RegionsLeaves of Arid Regions - Many have thick, leathery - Many have thick, leathery

leaves and few stomata. leaves and few stomata. - Some have succulent, water-- Some have succulent, water-

retaining leaves, or dense, hairy retaining leaves, or dense, hairy coverings. coverings.

Other structures for Other structures for comparisoncomparison

TendrilsTendrils

- Modified leaves - Modified leaves that curl around more that curl around more rigid objects helping rigid objects helping the plant to climb or the plant to climb or support weak stems.support weak stems.

1. Become 1. Become coiled like a spring as they coiled like a spring as they develop.develop.

2. When contact 2. When contact is made, the tip curls is made, the tip curls around the object, and around the object, and the direction of the coil the direction of the coil reverses. reverses.

example: example: MakahiyaMakahiya

Spines, Thorns, and PricklesSpines, Thorns, and Prickles

1. Spines - Modified leaves 1. Spines - Modified leaves designed to reduce water loss and designed to reduce water loss and protect from herbivory. protect from herbivory.

2. Thorns - Modified stems 2. Thorns - Modified stems arising in the axils of leaves of woody arising in the axils of leaves of woody plants. plants.

3. Prickles - Outgrowths from the 3. Prickles - Outgrowths from the epidermis or cortex. epidermis or cortex.

Storage Leaves - Storage Leaves - Succulents Succulents

Flower-Pot Leaves - Flower-Pot Leaves - Urn-Like Pouches Urn-Like Pouches

Window Leaves - Window Leaves - Leaves buried in Leaves buried in ground. ground.

Reproductive Reproductive Leaves - New plants Leaves - New plants at tips. at tips.

Floral Leaves - Floral Leaves - Bracts Bracts Example of storage leaves -

onion

Other succulent leavesOther succulent leaves

Aloe mitriformis

Selaginella

Bracts – ex Poinsettia

• Insect-Trapping LeavesInsect-Trapping Leaves

a. a. Pitcher Plants b. Butterworts b. Butterworts ––(Pinguicula(Pinguicula sp)

d. d. BladderwortsBladderworts b. b. Sundews

c. c. Venus’s Flytraps