1. LEAVES: FORM & FUNCTION
• Defination
• Function
• External Anatomy
• Internal Anatomy
• Specialized Leaves
2. The Plant Body: Leaves
• Defination: is green flatened outergrowth
of the stem or branch developing from a
node.
• FUNCTION OF LEAVES
– Photosynthesis
– Gaseous exchange
– Transpiration (excess water absorbed by
root, evaporate that through lower
surface of leaf)
– Storage of food(flashy leaf : aloe)
– Vegetative propogation (fern)
– Protection(by stipules-Acacia)
– Support(tendrils)
– Polination (attracting insect by color)
3. Uses of leaves
• As a source of food
• As a source of fiber
• As a fodder
• As a dye
• Ornamental purpose(house)
• Purgative
• Cardiotonic
• expectorant
• Fenugreek
• Banana
• Grasses
• henna
• Croton
• Senna
• Digitalis
• Vasaka
4. EXTERNAL ANATOMY
• Leaves possess a blade or lamina, an
edge called the margin of the leaf, the
veins (vascular bundles), a petiole, and
two appendages at the base of the
petiole called the stipules.
• Petiole: attaches leaf blade to stem
• Petiolate(present) & sessile(absent)
5. Parts of leaves
• Apex
– Tip of leaf
• Base
– Attaches to petiole – if petiole is absent,
attaches directly to stem
• Margin
– Edge of leaf
• Epidermis
– “Skin” of leaf - responsible for gas exchange
• Stomata
– Outside layer of leaf opening in epidermis
where gas and water exchange
• Mesophyll
– Middle layer of leaf where photosynthesis
occurs
7. Leaf types - Simple, compound, peltate and perfoliate
• Simple leaf = undivided blade with a single auxiliary bud at the
base of its petiole.
• Compound leaf = blade divided into leaflets, leaflets lack an
auxiliary bud but each compound leaf has a single bud at the
base of its petiole
– pinnately- Pinnately compound Leaves have the leaflets
arranged along the main or mid-vein. Odd pinnate With a
terminal leaflet; e.g., Fraxinus (ash).Even pinnate lacking a
terminal leaflet; e.g., Swietenia (mahogany).
– palmately-compound leaves: leaflets attached at the same
point at the end of the petiole; like fingers of the palm of a
hand. examples of plants with this leaf type include buckeye,
horse chestnut, hemp or marijuana, and shamrock.
• Perfoliate leaves = sessile leaves that surround and are pierced
by stems; examples include yellow-wort and thoroughwort
8. • Bipinnately compound Leaves are twice divided: the leaflets
are arranged along a secondary vein that is one of several
branching off the rachis. Each leaflet is called a "pinnule". The
group of pinnules on each secondary vein forms a "pinna";
e.g., Albizia (silk tree).
• Trifoliate (or trifoliolate)A pinnate leaf with just three
leaflets; e.g., Trifolium (clover), Laburnum (laburnum)
• Pinnatifid Pinnately dissected to the central vein, but with the
leaflets not entirely separate; e.g., Polypodium, some Sorbus
(whitebeams).
10. Peltate & Perfoliate Leaves
Mayapple Yellow Wort
Peltate leaves = petioles that are
attached to the middle of the blade;
e.g. include mayapple
Perfoliate leaves = sessile leaves
that surround and are pierced by
stems; e.g. include yellow-wort and
thoroughwort
11.
12.
13.
14.
15. Venation = arrangement of veins in a leaf
• Netted-venation = one or a few prominent midveins from which
smaller minor veins branch into a meshed network; common to
dicots and some nonflowering plants.
– Pinnately-veined leaves = main vein called midrib with
secondary veins branching from it (e.g., elm).
– Palmately-veined leaves = veins radiate out of base of blade
(e.g., maple).
• Parallel venation = characteristics of many monocots (e.g.,
grasses, cereal grains); veins are parallel to one another.
• Dichotomous venation = no midrib or large veins; rather
individual veins have a tendency to fork evenly from the base of
the the blade to the opposite margin, creating a fan-shaped leaf
(e.g., Gingko).
17. Image Term Description
Arcuate Secondary arching toward the apex
Dichotomous Veins splitting in two
Longitudinal All veins aligned mostly with the midvein
Palmate
Veins coming from one point like fingers come
from the palm of the hand
Parallel All veins parallel and not intersecting
Pinnate Secondary veins borne from midrib
Reticulate All veins branching repeatedly, net veined
Rotate
Veins coming from the center of the leaf and
radiating toward the edges
Transverse
Nervure tertiaire reliant les nervures
secondaires
18. phyllotoxy
• Different terms are usually used to describe the arrangement of leaves on
the stem (phyllotaxis):
• The leaves on this plant are arranged in pairs opposite one another, with
successive pairs at right angles to each other (decussate) along the stem.
Note the developing buds in the axils of these leaves.
• AlternateLeaf (Spiral) attachments are singular at nodes, and leaves
alternate direction, to a greater or lesser degree, along the stem.
BasalArising from the base of the stem. Cauline Arising from the aerial
stem.
• Opposite Two structures, one on each opposite side of the stem, typically
leaves, branches, or flower parts. (Decussate & superposed)
• Whorled, or verticillate Three or more leaves attach at each point or node
on the stem. As with opposite leaves, successive whorls may or may not be
decussate, rotated by half the angle between the leaves in the whorl (i.e.,
successive whorls of three rotated 60°, whorls of four rotated 45°, etc.).
Opposite leaves may appear whorled near the tip of the stem.
24. Specialized or Modified Leaves
• Cotyledons: embryonic or "seed" leaves. First leaves produced by a
germinating seed, often contain a store of food (obtained from the
endosperm) to help the seedling become established.
• Tendrils - blade of leaves or leaflets are reduced in size, allows
plant to climbing to other objects (e.g., sweet pea and garden peas. )
• Shade leaves = thinner, fewer hairs, larger to compensate for less
light; often found in plants living in shaded areas.
• Drought-resistant leaves = thick, sunken stomata, often reduced in
size
– In American cacti and African euphorbs, leaves are often reduced
such that they serve as spine to discourage herbivory and reduce
water loss; stems serve as the primary organ of photosynthesis.
– In pine trees, the leaves are adapted to living in a dry
environment too. Water is locked up as ice during significant
portions of the year and therefore not available to the plant; pine
leaves possess sunken stomata, thick cuticles, needle-like
leaves, and a hypodermis, which is an extra cells just underneath
the epidermis -
25. • Prickles and thorns: epidermal outgrowths on stems and
leaves (e.g., holly, rose, and raspberries; Hypodermic
trichomes on stinging nettles.
• Storage leaves succulent leaves retain water in large
vacuoles.
• Reproductive leaves, (e.g., Kalanchöe plantlets arise on
margins of leaves.
• Insect-trapping leaves: For example: pitcher plants,
sundews venus flytraps, and bladderworts have modified
leaves for capturing insects; All these plants live under
nutrient-poor conditions and digest insect bodies to obtain
nitrogen and other essential nutrients.
• Bracts: petal-like leaves.
• Window Leaves: plant is buried in soil with transparent
part exposed to light. Being buried reduces loss of war in
arid environments.
• Flower pot leaves: Structure to catch water and debris for
nutrient collection - fairy-elephant's feet.
31. • Monocot Leaf
• Symmetry: Isobilateral
• Stomata distribution: Amphistomatic i.e., stomata equally distributed on
both the surfaces.
• Bulliform cells: Present on upper epidermis.
• Mesophyll: Only spongy parenchyma is present which has very small
intercellular spaces.
• Bundle sheath: Made of parenchyma but just above and below the vascular
bundles are found sclerenchymatous cells (upto epidermis)
• Dicot Leaf
• Symmetry: Dorsiventral
• Stomata distribution: Hypostomatic i.e., stomata present on lower surface
of leaf.
• Bulliform cells: Usually absent.
• Mesophyll: Made up of two types of tissues: Palisade parenchyma and
spongy parenchyma with large intercellular spaces.
• Bundle sheath: Made up of parenchyma. Just above and below the vascular
bundle some parenchymatous cells or collenchymatous cells are present up
to epidermis.
32.
33. MONOCOTS DICOTS
Embryo with single cotyledon Embryo with two cotyledons
Pollen with single furrow or pore Pollen with three furrows or pores
Flower parts in multiples of three Flower parts in multiples of four or five
Major leaf veins parallel Major leaf veins reticulated
Stem vacular bundles scattered Stem vascular bundles in a ring
Roots are adventitious Roots develop from radicle
Secondary growth absent Secondary growth often present
34. R00T
• Roots absorb water, minerals, and nutrients from the soil, and they
anchor the plant to the ground or other substrate.
• They often lack coloration, but sometimes they may be highly
colored (carrots for example).
• They lack leaves, nodes, and internodes.
• Roots are often found at the very bottom of the plant, below the soil
level. However, they can also emerge from stem tissue - often at
nodes (think of the ivy plants that you see around town - their roots
anchor their climbing stems to the walls of fences or houses).
35.
36. TYPES OF ROOT SYSTEMS
G
TAP ROOTS FIBROUS ROOTS ADVENTIOUS ROOTS
•Prominent in dicot •Prominent in monocots •They develop from
organs
•Primary roots grow &
becomes stout.
•Roots develop from lower
nodes
Of shoot system
•Secondary & tertiary
grow from primary root
•They have same length &
diameter
37. Roots
Taproot System
Primary roots grow
down from the stem
with some
secondary roots
forming
Image found at: http://www.arboretum.fullerton.edu
39. Root Functions
• Absorption of water and nutrients
– performed by root hairs
• Transportation of water and
nutrients to stem
• Anchor plant to maintain stability
• Store food and water
Roots have 4 primary functions
40. Parts of the Root
• Epidermis
– Outermost layer of cells, like the skin of the
root
• Cortex
– Tissue inside epidermis that stores starch
and other substances for the growth of the
root
41. Parts of the Root
1) Root Cap: covered over the apex by
cap.
• Absent in aquatic plant
• Provides protection for the root tip
2) Region of cell division:
• Growing apex of root, just beyond root
cap
3) Region of elongation:
• Lies above the meristmatic region &
extend to a length of few mm.
4)Root Hairs
• Site of absorption (water & mineral salt)
5)Vascular Tissue
• Within cortex, contains cells that
transport water, nutrients, and minerals
to all parts of the plant
57. Functions of the
Stem• Transport water
and nutrients from
roots to leaves
• Supports leaves,
fruit, and flowers
• Food storage
Image found at: www.karencarr.com
58. Parts of the
Stem
• Node
– Areas where side branches
and leaves develop
• Internode
– Area between nodes
• Xylem
– Carries nutrients up
• Phloem
– Carries nutrients down
• Pith
– Stores food
Image found at: www.ext.colostate.edu
