LEAVES

Leaf Structure:
A leaf is made of many layers that are sandwiched between two layers of tough skin cells (called the epidermis). The epidermis also secretes a waxy substance called the cuticle. These layers protect the leaf from insects, bacteria, and other pests. Among the epidermal cells are pairs of sausage-shaped guard cells. Each pair of guard cells forms a pore (called stoma; the plural is stomata). Gases enter and exit the leaf through the stomata.
Most food production takes place in elongated cells called palisade mesophyll. Gas exchange occurs in the air spaces between the oddly-shaped cells of the spongy mesophyll.
Veins support the leaf and are filled with vessels that transport food, water, and minerals to the plant.

Leaf Glossary:
air space - intercellular gaps within the spongy mesophyll. These gaps are filled with gas that the plant uses (carbon dioxide - CO2 ) and gases that the plant is expelling (oxygen - O2, and water vapor).
axil - the angle between the upper side of the stem and a leaf or petiole.
cuticle - the waxy, water-repelling layer on the outer surface of a leaf that helps keep it from dying out (and protect it from invading bacteria, insects, and fungi). The cuticle is secreted by the epidermis (including the guard cells) and is often thinner on the underside of leaves. The cuticle is generally thicker on plants that live in dry environments.
epidermis - the protective, outer layer of cells on the surface of a leaf. The guard cells (and stoma) are part of the epidermis. The surface of many leaves is coated with a waxy cuticle which is secreted by the epidermis.
guard cell - one of a pair of sausage-shaped cells that surround a stoma (a pore in a leaf). Guard cells change shape (as light and humidity change), causing the stoma to open and close.

leaf apex - the outer end of a leaf; the end that is opposite the petiole.
mesophyll - the chlorophyll-containing leaf tissue located between the upper and lower epidermis. These cells convert sunlight into usable chemical energy for the plant.
midrib - the central rib of a leaf - it is usually continuous with the petiole.
palisade mesophyll - a layer of elongated cells located under the upper epidermis. These cells contain most of the leaf's chlorophyll, converting sunlight into usable chemical energy for the plant.

Leaf Anatomy
Leaf anatomy is correlated to photosynthesis:
Carbon dioxide + Water ? sugars + oxygen
dermal
ground
vascular
dermal

Leaf epidermis
Is transparent – so that sun light can go through.
Waxy cuticle protects against drying out
Lower epidermis: stomata with guard cells – for gas exchange (CO2, H2O in; O2 out)

Structure of the Stomata
A stoma or pore is formed by a pair of bean-shaped guard cells. The guard cells have the ability to open and close the stoma. The inner walls of the guard cells are thick and the outer walls thin. Guard cells differ from the translucent epidermal cells in that they contain chloroplasts.
Stomata communicate with the air chambers in the spongy mesophyll.
There are more stomata on the lower epidermis of the leaf than the upper epidermis.
Certain terminology is associated with their location; if they occur on both surfaces of a leaf, the plant is amphistomatic; if they occur on the upper surface only, it is epistomatic; and lower surface only is hypostomatic.
Functions:
The stomata are responsible for the interchange of gases for respiration and photosynthesis.
The stomata allow for the loss of excess water in the form of water vapour, which also allows for cooling.
The various types of stomata present in a plant are:
1)Paracytic stomata 2)Dіacytic stomata 3)Anisocytic stomata 4)Anomocytic stomata 5)Actinocytic stomata

Stomata type
Anomocytic: The stomata are anomocytic in which the guard cells are not surrounded
with any subsidiary cell (surrounded by five unspecialized epidermal cells)
.
Species included: Aerva javanica (Burm.f.) Juss., Amaranthus graecizans L., Amaranthus viridis L., Pupalia lappacea (L.) Juss. Cassia holosericea Fres., Parkinsonia aculeata L. (Caesalpiniaceae), Lactuca remotiflora DC., Euphorbia hirta Forssk., Phyllanthus niruri L.(Euphorbiaceae), Enicostemma verticillatum (L.) Engler (Gentianaceae), Salviasantolinaefolia Boiss. (Labiatae), Anagallis arvensis L.(Primulaceae), Zizyphus nummularia (Burm.f.)(Rhamnaceae), Datura alba Nees, Lycium europium L., Tribulus terrestris L., Zygophyllum simplex L. (Zygophyllaceae).

Anisocytic: In anisocytic type the guard cells are surrounded by three unequal sized subsidiary cells, the common wall of which is at right angle to the longitudinal axis of stoma.
Species included: Farsitia jacquemontii Hook.f. et. Thoms. (Cruciferae)
Paracytic: In the paracytic type guard cells are accompanied by two subsidiary cells, the longitudinal axis of which are parallel to that of the guard cells and aperture.
Species included: Cleome brachycarpa Vahl (Capparidaceae), Convolvulus glomeratus(Convolvulaceae), Andrachne aspera Spreng.
(Euphorbiaceae), Oxalis corniculata L. (Oxalidaceae), Phaseolus trilobus (L.) DC.(Papilionaceae).
Diacytic: Diacytic stomata are those in which one or more pairs of subsidiary cells enclose the stoma and the common wall of subsidiary cells are at right angles to the guard cells.
Species included: Blepharis sindica Stocks ex T. Anderson., Ruellia tuberosa L.,
Ruellia patula Jacq. (Acanthaceae).

Parallelocytic: In parallelocytic stomata, an alternating complex of three or more cshaped
subsidiary cells is present.
Species included: Portulaca oleracea L. (Portulacaceae).
Cyclocytic: In cyclocytic type two or more subsidiary cells form one or two narrow rings
around the guard cells.
Species included: Ipomoea carnea Jacq. (Convolvulaceae)

Leaf facial symmetry and insolation response; some plants grow their leaves with distinctly different sides for sun or shade exposure. Plants that hold one leaf face to flat to the sunlight usually have stomata only or mostly on the underface (abaxial). The abaxial surface of a leaf is the underside or side facing away from the stem. The sunward adaxial surface has a thicker waxy coating and typically has fewer stomata.
Unifacial leaves are both abaxial sided with plentiful stomata. The leaves hang vertically to expose less area directly to the drying sun. They have ~equal numbers of stomata on both faces of the leaf.

The vertical section of a dorsiventral leaf through the lamina shows three main parts, namely, epidermis, mesophyll and vascular system. The epidermis which covers both the upper surface (adaxial epidermis) and lower surface (abaxial epidermis) of the leaf has a conspicuous cuticle. The abaxial epidermis generally bears more stomata than the adaxial epidermis.
The anatomy of isobilateral leaf is similar to that of the dorsiventral leaf in many ways. It shows the following characteristic differences. In an isobilateral leaf, the stomata are present on both the surfaces of the epidermis; and the mesophyll is not differentiated into palisade and spongy parenchyma
.

Leaf epidermis
Trichomes
(“Panda plant”)
Grandular Simple

Leaf Mesophyll
Middle of the leaf (meso-phyll)
Composed of photosynthetic ground cells:
Palisade parenchyma
(long columns below epidermis;
have lots chloroplasts for
photosynthesis)
Spongy parenchyma
(spherical cells)
with air spaces around,
(for gas exchange)

Functions of the Mesophyll
The palisade cells are responsible for photosynthesis because they contain chloroplasts.
The spongy mesophyll, together with the intercellular air spaces, allow for the interchange of gases.

Leaf vascular tissue
VEINS ? vascular tissue of leaves.
Veins are composed of xylem (water transport) phloem (food transport)
and bundle sheaths,
cells surrounding the
xylem/phloem for
strength & support
The lignified xylem cells are situated towards the upper epidermis and the phloem towards the lower epidermis.

Venation
pinnate - single main (primary) vein with secondary veins branching from it like a feather
palmate - several primary veins arising from a common point
parallel - primary and secondary veins parallel to one another. The parallel venation in monocot leaves is reflected in the near similar sizes of vascular bundles (except in main veins) as seen in vertical sections of the leaves
net or reticulate venation - general term for pinnate or palmate pattern of veins.

Structure of leaves

Morphology
simple leaf - a single blade, not divided into sections.
compound leaf - leaf blade is divided into leaflets, all the way down to the midrib (which is called the rachis in a compound leaf).

Leaf structure
simple - leaf blade all one section (а)
lobed leaf - the margin of the leaf is indented, but not all the way to the midrib (d)
dissected - leaf divided into very fine, somewhat indistinct segments (C)
parted (or cleft) - the margins between the irregular teeth go more than halfway to the midrib (b)
(d)

compound - leaf blade divided into smaller sections called leaflets
leaflet - section of a compound leaf
rachis - stalk that supports leaflets in a compound leaf; central axis
rachilla - stalk that supports lateral leaflets
pinnately compound - like a feather
palmately compound - like the fingers on your hand
petiole - a leaf stalk; it attaches the leaf to the plant.

Leaf Margins:
Leaves come in many sizes and shapes; they are often used to help identify plants. Some leaves are flat and wide; others are spiky and thin. Plant spines (like cactus spines) are actually modified leaves.

Leaves showing various morphologies. Clockwise from upper left: tripartite lobation, elliptic with serrulate margin, peltate with palmate venation, acuminate odd-pinnate (center), pinnatisect, lobed, elliptic with entire margin
acuminate: long-pointed, prolonged into a narrow, tapering point in a concave manner.
acute: ending in a sharp, but not prolonged point
cuspidate: with a sharp, elongated, rigid tip; tipped with a cusp.
emarginate: indented, with a shallow notch at the tip.
mucronate: abruptly tipped with a small short point, as a continuation of the midrib; tipped with a mucro.
mucronulate: mucronate, but with a smaller spine.
obcordate: inversely heart-shaped, deeply notched at the top.
obtuse: rounded or blunt
truncate: ending abruptly with a flat end, that looks cut off.

Arrangement
Leaves may be found only at the base of the plant (basal, rosette, as in dandelion) or along the stem (cauline) or some combination. Leaves are attached at nodes:
alternate - one leaf per node
opposite - two leaves per node; help remember temperate woody plants with opposite leaves (M=maple; A=ash; D=dogwood)
whorled - more than two leaves per node; not common in temperate woody plants

Arrangement leafs on the stem
Alternate — leaf attachments are singular at nodes, and leaves alternate direction, to a greater or lesser degree, along the stem.
Opposite — leaf attachments are paired at each node; decussate if, as typical, each successive pair is rotated 90° progressing along the stem; or distichous if not rotated, but two-ranked (in the same geometric flat-plane).
Whorled — 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.
Rosulate — leaves form a rosette

BILBERRY LEAF (Myrtilli folium)
USES: Bilberry leaf has been used for diabetes, stomach problems, arthritis, blood circulation problems, and heart problems.
Red raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrheaRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory systemRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including fluRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine fluRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine flu; and for heartRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine flu; and for heart problems, fever, diabetesRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine flu; and for heart problems, fever, diabetes, and vitamin deficiency. It is also used to promote sweatingRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine flu; and for heart problems, fever, diabetes, and vitamin deficiency. It is also used to promote sweating, urination, and bile production. Some people use it for general "purification of skinRed raspberry leaf is used for gastrointestinal (GI) tract disorders, including diarrhea; for respiratory system disorders, including flu and swine flu; and for heart problems, fever, diabetes, and vitamin deficiency. It is also used to promote sweating, urination, and bile production. Some people use it for general "purification of skin and blood.”

Khat (Catha edulis; "edible kat") is a flowering plant native to the Horn of Africa and the Arabian Peninsula. The leaf and stem are used as a recreational drug and as medicine.
As a recreational drug, the leaves and stem are chewed by people in East Africa and the Arabian countries to elevate mood (as a euphoriant).
As a medicine, khat leaf is used for depressionAs a medicine, khat leaf is used for depression, fatigueAs a medicine, khat leaf is used for depression, fatigue, obesityAs a medicine, khat leaf is used for depression, fatigue, obesity, stomachAs a medicine, khat leaf is used for depression, fatigue, obesity, stomach ulcers, and male infertility. It is also used to lower the
Senna is a natural medicine containing sennosides that are derived from the leaves of the senna plant. Sennosides irritate the lining of the bowel causing a laxative effect.
Senna has been used in alternative medicine as a laxative and an aid to treat constipation