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Introduction to Botany:
Definition:
Botany/plant biology/phytology is a branch of biology which deals with the scientific
study of plant life.
History in brief:
Botany appears to have had originated as far back as the Stone Age. Early man's
interest may have been simply to learn what different herbs and plants could be used
as food. This could be seen as an early and basic form of plant classification,
grouping them as edible and inedible. Written manuals for the use of herbs in
medicine existed as far back as 3000 BC in Mesopotamia and China. While the
Egyptians also wrote much on the medicinal uses of plants the study of botany, the
earliest written botanical information that we possess today came from the Greeks.
The term “botany” came form Greek word botanikos (botanical) and botane(plant or
herb).Although Aristotle, the great Greek Philosopher ,was the one who collected the
information about the plants ,it was his student Theophrastus who elaborately worked
on his information and devised more complex system of plant classification(Histortia
plantarum)
Thus he is referred to as the “Father of Botany.”
Branch of Botany:
 Agronomy—Application of plant science to crop production
 Bryology—Mosses, liverworts, and hornwarts
 Economic botany—The place of plants in economics
 Ethnobotany—Relationship between humans and plants
 Forestry—Forest management and related studies
 Horticulture—Cultivated plants
 Paleobotany—Fossil plants
 Palynology—Pollen and spores
 Phytochemistry—Plant secondary chemistry and chemical processes
 Phytomorphology—Structure and life cycles
 Plant anatomy—Cell and tissue structure
 Plant ecology—Role of plants in the environment
 Plant genetics—Genetic inheritance in plants
 Plant pathology—Plant diseases
 Plant systematics—Classification and naming of plants
 Physiology-Study of functions of different parts of plant.
 Histology-Study of cells and tissues.
 Pathology-Study of diseases of plant.
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Field Botany: Botany in the Wild
What is Field Botany?
It mainly consists of fieldwork of observation, describing the morphology of plants,
identification, classification of plants and assigning of family. Botanists take to the
field to bring home new varieties of flowering and non-flowering plants for study and
to further expand their knowledge of plants. Many of these plants provide new food
sources or medicines. All provide insight into the complexity of the living world. As
Thomas Jefferson noted: "The greatest service which can be rendered to any country
is to add a useful plant to its culture..." [The Jeffersonian Cyclopedia, 1900]
Besides the possible agricultural or medicinal value that these finds bring, there is
also an element of excitement in being the first to find and identify a new species of
plant. Roland Thaxter (1858-1932), Professor of Cryptogamic Botany and Curator of
the Farlow Herbarium at Harvard, stated in a diary entry from his 1905 collecting trip
to South America, "The heart of Smith, poor man, could not beat in unison with the
sensation of a botanist at the moment of his first contact with a wholly strange flora."
Linnaeus, who is often called the Father of Taxonomy, was one of the first botanists
to embrace the practice of extensive travel for fieldwork. It is reported that between
1745 and 1792 nineteen of Linnaeus's students went of to distant lands to collect new
plant specimens. Half of these students perished. Many died of fever, some were
never heard from again and a few went insane.
Fieldwork took another giant step forward when, in 1768, James Cook set aboard the
Endeavor on a scientific mission. With him were the young naturalists Joseph Banks
and Daniel Charles Solander (a pupil of Linnaeus) as well as team of artists. In April
1770 the ship arrived in Botany Bay, so named because of the fabulous amount of
new plants collected by Banks and Solander.
In the 19th century botanists began to travel to more and more remote locations. They
traveled all over Africa, Asia, Antarctica, Australia, Europe, North America, and
South America in their search of plants, animals, and minerals for agriculture and for
medicine. This increased knowledge has helped us to "master" the living world.
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Components of Field Botany
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Plant Morphology
Plant taxonomy
Plant Herbarium.
Plant Morphology:
It is the study of external characteristics of the plants such as:
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Root
Stem
Leaves
Flowers
Fruits.
Root:
General description:
Typically root is an underground part of a plant that generally lack chlorophyll.
However it is of exception with some plants having aerial roots. We can therefore
define root as the part of a plant body that bears no leaves and internodes.
Characteristics of roots:
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It is geotropic (Growing downwards)
It is always non-green due to lack of chlorophyll.
Doesn’t bear leaves, flowers, buds etc.
Tips are protected with root cap.
Bears root hairs
Function of root:
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Anchorage
Absorption of minerals and salt
Storage of food and water.
Floatation
Respiration
Propagation
Photosynthesis.
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Types of roots
A true root system consists of a primary root and secondary roots (or lateral
roots).The primary root originates in the radicle of the seedling. During its growth it
rebranches to form the lateral roots. Generally, two categories are recognized:
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the taproot system: the primary root is prominent and has a single, dominant axis;
there are fibrous secondary roots running outward. Usually allows for deeper
roots capable of reaching low water tables. Most common in dicots. The main
function of the taproot is to store food.
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the diffuse root system: the primary root is not dominant; the whole root system is
fibrous and branches in all directions. Most common in monocots. The main
function of the fibrous root is to anchor the plant.
Specialized roots
The roots, or parts of roots, of many plant species have become specialized to serve
adaptive purposes besides the two primary functions described in the introduction.
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Adventitious roots arise out-of-sequence from the more usual root formation of
branches of a primary root, and instead originate from the stem, branches, leaves,
or old woody roots. They commonly occur in monocots and pteridophytes, but
also in many dicots, such as clover (Trifolium), ivy (Hedera), strawberry
(Fragaria) and willow (Salix). Most aerial roots and stilt roots are adventitious. In
some conifers adventitious roots can form the largest part of the root system.
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Aerating roots (or pneumatophores): roots rising above the ground, especially
above water such as in some mangrove genera (Avicennia, Sonneratia). In some
plants like Avicennia the erect roots have a large number of breathing pores for
exchange of gases.
Aerating roots of a mangrove
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Aerial roots: roots entirely above the ground, such as in ivy (Hedera) or in
epiphytic orchids. They function as prop roots, as in maize or anchor roots or as
the trunk in strangler fig.
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Buttress roots or tabular roots: support roots for many tropical tree species.
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Contractile roots: they pull bulbs or corms of monocots, such as hyacinth and
lily, and some taproots, such as dandelion, deeper in the soil through expanding
radially and contracting longitudinally. They have a wrinkled surface.
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Coarse roots: Roots that have undergone secondary thickening and have a woody
structure. These roots have some ability to absorb water and nutrients, but their
main function is transport and to provide a structure to connect the smaller
diameter, fine roots to the rest of the plant.
Fine roots: Primary roots usually <2 mm diameter that have the function of water
and nutrient uptake. They are often heavily branched and support mycorrhizas.
These roots may be short lived, but are replaced by the plant in an ongoing
process of root 'turnover'.
Haustorial roots: roots of parasitic plants that can absorb water and nutrients
from another plant, such as in mistletoe (Viscum album) and dodder.
Propagative roots: roots that form adventitious buds that develop into
aboveground shoots, termed suckers, which form new plants, as in Canada thistle,
cherry and many others.
Proteoid roots or cluster roots: dense clusters of rootlets of limited growth that
develop under low phosphate or low iron conditions in Proteaceae and some
plants from the following families Betulaceae, Casuarinaceae, Eleagnaceae,
Moraceae, Fabaceae and Myricaceae.
Stilt roots: these are adventitious support roots, common among mangroves.
They grow down from lateral branches, branching in the soil.
Storage roots: these roots are modified for storage of food or water, such as
carrots and beets. They include some taproots and tuberous roots.
Structural roots: large roots that have undergone considerable secondary
thickening and provide mechanical support to woody plants and trees.
Surface roots: These proliferate close below the soil surface, exploiting water
and easily available nutrients. Where conditions are close to optimum in the
surface layers of soil, the growth of surface roots is encouraged and they
commonly become the dominant roots.
Tuberous roots: A portion of a root swells for food or water storage, e.g. sweet
potato and dahlia. A type of storage root distinct from taproot.
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Recommended website and references:
http://en.wikipedia.org/wiki/Root
http://facweb.furman.edu/~lthompson/bgy34/plantanatomy/plant_root.htm
http://www.ffp.csiro.au/research/mycorrhiza/root.html
http://www.botgard.ucla.edu/html/botanytextbooks/generalbotany/typesofroots/index.
html
http://en.wikipedia.org/wiki/Botany
http://waynesword.palomar.edu/bot115.htm
http://aob.oxfordjournals.org/
http://arnica.csustan.edu/boty3700/lectures/lecture_notes.htm
http://www.puc.edu/Faculty/Gilbert_Muth/botsyllecture.htm
http://www.csdl.tamu.edu/FLORA/Wilson/tfp/hdwtfpbs01.htm
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Stem
General description:
It is one of the two main structural axes of a vascular plant. The plumule of a seed
develops into stem. The stem is normally divided into nodes and internodes, the nodes
hold buds which grow into one or more leaves, inflorescence (flowers), cones or other
stems etc. Stems bear branches and leaves that are together called shoot.
A:Forms of stems:
In general the stems are cylindrical, yet the following types of stem forms are
distinguishable.
Square:
Four angled forming a square
Triangular:
Three angled stem.
Flat:
Flat and leaflike structure.
Jointed:
Also called as articulated, has a number of joints or articulations
in the nodes which bulges externally forming a hardened ring.
Ribbed:
Stems with ridges and furrows e.g. Cucurbita spp.
Ribbon shaped:
Stem is flat or ribbon shaped.
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B: Surface of the stems:
Glabrous:
Surface of the stem is smooth.
Glaucous:
Smooth and shiny stem.
Pubescent or tomentose: Stems with various types of hairs.
Prickly or spiny: Prickles and spines are present.
C: Nature and pattern of the stem:
According to nature, mode and branching pattern of stems, plants are divided into:
I. Herbs: Erect plants with soft stems and small size structure. They generally
consist of few branches or no branches. Depending upon the duration of life they are
of the following types:
Ephemerals: - They survive only for a few days during
which they complete their life cycle e.g. Balanites.
Annuals: - They live and complete their life cycle through
one season only e.g. Oryza sativa (rice).
Biennials: - They live through two successive seasons during
which they complete their life cycle e.g. Raphanus sativa
(radish).
Perennials: - They live and complete their life cycle in more
than one season e.g. Zinziber officinale (zinger).
II. Shrubs: These are small/medium sized erect woody plants. They are profusely
branched e.g. Hibiscus rasa-sinensis.
III. Under shrubs: Those plants whose character falls in between the shrubs and the
herbs are called as under shrubs e.g. Capsicum fruticens (chilli)
IV. Trees: These are tall plants with very hard and woody stems.
Note: the above classification is arbitrary and is therefore subjective.
D: Kinds of stems:
I. Strong
Strong plants are erect and remain in upright position due to their rigidity. They
are of different types:
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Excurrent:
Trees with pyramidal forms due to their racemose types of branching. Pine tree.
Deliquescent: Dome shaped or rounded appearance.
Caudex:
Tall trees with out the branchings are called caudex e.g. Palm
Culm:
Plants with jointed stems are known as culm e.g. Bamboo.
Scape:
These are the erect and unbranched stems produced by the
suppressed under ground stems. They come up through the
clusters of leaves and bear at the apices either solitary flowers
cluster of flowers. Found in monocotyledons e.g. Onions.
II. Weak:
Weak stems are those stems that are not able to stand erect themselves. They are
either:
Trailers,
creepers or
Climbers
Trailers: Trails (spreads) over the surface of the ground with out the roots on the
nodes. They are of two types:
Prostrate/procumbent: When the plant lies flat on the ground surface along
with the apex.
Decumbent: Plant lies on the ground flat with the apex turned upward.
Creepers: Plants spread horizontally over the ground in all direction and produces
roots from each nodes. e.g. Ipomoea batata (sweet potato).
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Climbers: These plants climb up the other plants or object for support. The
following types are noted:
Stem climbers or twiners:- Weak, long and slender stems of some plants
climb up other plants or object by twining round their own stems. They are
of the following types:
Dextrorse:- The twiners climb up by twining clock wise or to the
right e.g. Dolichus (bean).
Sinistrorse:- The twiner twine anti-clock wise or to the left e.g.
Ipomoea quamoclit.
Lianes:- Long and woody climbers which climb up the tall forest trees.
Tendril Climbers:- Special climbing organs are developed by some of the
plants which are called as tendrils. These tendrils are slender, spirally coiled,
thread like structures and modified leaflets, leaves, branches or even
inflorescence.
Root climbers:- They have adventitious roots developed from the nodes for
climbing up the other plants.
Other types of climbers include hook climbers, ramblers or scramblers
and adhesive climbers.
E: Functions of stems:
Normal and Special function.
I: Normal functions:
Mechanical function:- the bearing of the crown and weight of the entire plant.
Physiological functions:- Conduction of mineral salts and water absorbed by the
roots and translocation of the prepared food materials.
II: Special functions:
Storage of water:- done by special water storage tissue present below the
epidermis.
Storage of food:- Mainly carried out by the underground modified stems like
rhizomes, tubers and corms.
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Photosynthetic function:- Manufacture of carbohydrate food particularly by the
phylloclades.
Self defence:- By the development of thorns and prickles, mainly against grazing
animals
Propagation or reproductive:- Sub aerial modified stems helping in vegetative
propagation.
Bud:
These are condensed young shoots. There are different types of buds.
Leaf bud: - develops to a leaf.
Stem bud: - develops into a leafy branch.
Flower bud: - develops into a flower
Mixed bud: - develops into vegetative shoots and flowers. They are of the following
types:
Normal bud:- Situated either at the apex of the shoot or at the leaf axils.
There fore depending upon their locations they are either apical
(terminal) or Axillary . Apical buds are situated at the apex of the
elongating branch or stem. Where as the axillary buds are those which
are present at the leaf axils. The axillary buds are called as dormant
when they are not active and deciduous when they fall off from the
plants at early stage instead of developing into a shoot.When two or
more buds are situated side by side on a leaf axils they are called as
collateral. But when more then one buds are present one above the
other, they are called as superposed buds.
Adventitious bud: - Buds develop from other than the leaf axil and the
apex. They are of the following types:
Epiphylous: buds developing on leaves.
Cauline:- Buds developing on cut stem.
Radical buds: those developing on roots.
F: Stem modification:
Instead of stem growing upwards, they grow under ground and modify themselves to carry
out various functions and attain different shapes. They are mainly of the following types :
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Rhizomes:- Thick and fleshy under ground stem growing horizontally or sometimes
vertically. When the rhizomes grow vertically they are called as root stocks and
sobole when they grow horizontally and have long internodes e.g. Zinziber officinale
(zinger).
Stem tuber:- It is the swollen tip of the under ground branch which arises from the
leaf axil of the main stem. It has scales and buds e.g. Solanum tuberosum (potato).
Corm:- Enlarged, more or less round, solid and fleshy under ground stem growing
vertically which has few nodes and internodes e.g. Amorphophallus.
Bulb:- small modified disc like under ground stem. The stem is very much
reduced.The thick fleshy scale leaves grows above the disc shaped stem and stores
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food. Terminal bud is present at the centre of the thick scale leaves and axillary buds
in between the scale leave e.g. Onions.
Runner: - slender, prostrate, creeping aerial stem or branch. After running on the
ground surface for a few distance it produces new shoots and roots which in turn
becomes a new plant e.g. Oxalis, Centella asiatica.
Offset: - Similar to runner but the stem is shorter and thicker e.g. Eichornia.
Sucker: - Branch arising from stem below the surface of the earth. It grows for a
short distance and produces roots, turns upwards and come up to the surface e.g.
Chrysanthemum.
Stolon: - similar to runner but the stem is much slender and longer. The stolon
arches as it grows and as soon as it touches the ground it produces new shoots e.g.
Frageria (straw berry).
Thorn: - It is an axillary branch. Its further growth is checked and the tip ultimately
turns into a hard and sharp pointed structure e.g. Alangifolium.
Phylloclades and cladodes: - Flat leaf like modified stem or branch with several
nodes and internodes carrying out the function of the leaf. Leaves are reduced to
spines e.g. Opuntia (cactus).
Pseudobulb: - Fleshy aerial modified stem as seen in orchids. Its function is to store
moisture.
Bulbils: - These are aerial bulbs arising from the leaf or scale axils e.g. Lilium
bulbiferum.
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Stem or branch tendrils: - modified stem or branch which is slender and thread
like meant for the support of the weak stem e.g. Passiflora.
G: Branches:
These are the lateral appendages from the main stem having nodes and internodes. The
manner in which the branches are arranged is called as branching. There are two main
types of branching:
Lateral branching: - Branches develop laterally from the lateral buds of the main
stem.
Dichotomous branching: - The apical mass of tissue divides and bifurcates. This
bifurcation gives rise to two equal branches in a forked manner.
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LEAF(VES)
1. Types of leaves:
Leaves are of two types depending upon the nature of complexity:
Simple and
Compound leaves
Simple leaves
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consists of single lamina
single articulation
may be entire or incised but incision never touches the midrib or petiole
Compound leaves
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leaf blade broken up into a number of small segments called as leaflets
two or more articulation
incision touches the midrib or the petiole
leaflets are free from each others and arranged on the rachis
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2. Different types of compound leaves:
Pinnate and
Palmate
Pinnately compound leaves are those in which the leaflets are arranged either alternately or
in opposite pairs on both sides of the rachis (midrib) directly or on the branches of the
rachis. They are of the following types:
unipinnate:- when the rachis bears the leaflets directly then the leaf is called as
unipinnate. Two types of unipinnate leaves are:
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paripinnate(Evenpinate):- when the leaflets are in pairs i.e.
rachis bears even numbers of leaflets
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imparipinnate(Oddpinate): terminal end of rachis bears a
single leaflet
bipinnate:- secondary branches of midribs are produced which bears small leaflets
called as pinnules eg.
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tripinnate:- Leaflets are born by the tertiary branches.
decompound:- When the leaves are thrice pinnate.
Palmately compound leaves are those in which the terminal ends of the petioles bear a
number of articulations and leaflets which radiate from a common point. They are of the
following types:
Unifoliate:-When one leaf let is articulated at apex of the winged petiole.
Bifoliate:- When two leaflets are articulated to the apex of the petiole.
Trifoliate:- Three leaflets are articulated at the apex of the petiole
Quadrifoliate:- four leaflets are articulated at the apex of the petiole.
Digitate or multifoliate:- when more then four leaflets are arranged at the apex of
the petiole.
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3. Shape of the lamina or the leaf blade:
With reference to the general out line the following types are noted:
Acicular:
long needle like shape.
Linear:
Long narrow and flat leaf blades,
Lanceolate:
Shape of the leaf blade is like that of a lance, wider at the middle
of the blade and narrower at the apex and the base.
Oblong:
When the leaf blade is wide and long with two margins running
parallel.
Subulate:
leaf blade is long , narrow and gradually tapers from base to apex.
Ovate:
Egg shaped leaf blades (broader at the base than at apex).
Obovate:
When the leaf blade is inversely ovate.
Spathulate:
blade is broad and round at the apex and tapers narrowly
towards the base.
Cordate:
Leaf shape is heart shaped and deeply notched at the base.
Obcordate:
leaf blade is inversely heart shaped.
Sagittate:
arrow shaped leaf base i.e. when the apex is pointed and the two
basal lobes are pointed downwards.
Hastate:
Reniform:
leaf blade has two basal lobes pointed outwards.
Leaf blade is kidney shaped i.e. The apex is rounded and has a
deep notch at the base.
Lunate:
Half moon like leaf blade with two pointed basal lobes.
Cuneate:
wedge shaped, flat and broad with narrow base
Orbicular:
nearly circular leaf blades.
Oblique:
when the two halves of the lamina are not equal.
Elliptical:
leaf base more or less like an eclipse.
Falcate:
sickle shaped leaf blade.
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Lyrate:
4.
leaf blades have large rounded lobes towards the apex and two
or more lateral lobes towards the base.
The structure of leaf apices:
Various shapes are attained by the leaf apices. They are mainly of the following types:Acute:
The leaf apex is sharp and pointed, the sides of which are tapering
and somewhat convex.
Acuminate:
apex is acute but longer and the sides are bit concave.
Obtuse:
When the apex is blunt.
Caudate:
The apex is long, slender, tail like and terminating in a point.
Cirrhose:
apex terminating in a thread like structure.
Cuspidate:
apex is long, sharp and pointed with rigid tip.
Emarginate: apex with sharp triangular notch.
Mucronate:
round or blunt or flat apex having a short triangular point in the
middle
Retuse:
The leaf apex is obtuse with a broad shallow notch in the middle
Truncate:
The leaf apex is flat, more or less straight across or slightly concave.
5. Margins of leaf lamina:
Depending upon the absence or presence of the incision and the amount of the incision, leaf
margins are of the following types:
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Entire or even: Margin is even and smooth.
Repand or sinuate: Wavy or undulating leaf margins
Serrate:
Margin incised like the teeth of the saw
Dentate:
When the teeth of the leaf margins are sharp and pointed outward at
right angle to the margin
Crenate:
When the margins are toothed but the teeth are rounded
Spiny:
Margins of the leaf with large teeth like projection ending in spines.
Bi-serrate:
Margins are toothed but the teeth are again serrated.
Retroserrate: Like serrate but the teeth are pointed down ward.
Bi-dentate:
Margins are toothed but again dented.
Bi-crenate:
Teeth are crenate twice.
Lobed:
When the margins are deeply divided then each divisions of the
lamina are called as lobes. In this case the leaf blades are called
as lobed or incised..
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LEAF SHAPES
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APICES
BASES
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LEAF MARGINS
Ciliate
Serrate
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LEAF VENATION
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6. Modifications of leaves:
leaf tendrils:- The entire leaf is modified into a slender, thread like structure. Some
times the terminal leaflets are modified to form tendrils. They help the plant to climb
up the other plants.
Spine:- leaves modified into small sharp pointed structures. some times the margins
or the apex of the plants may modify into spines. They are the protective organs of
the plants against animals.
Phyllode:- It is the green flattened or winged modified petiole. Either the leaflets
drop very early or do not develop at all. They carry out the function of the normal
leaf.
Fleshy or succulent leaf:- It is a modified normal leaf. It helps in storage of water.
Hooks:- Leaves are modified into sharp and hard pointed structures whose tips are
bents. They are the organs for climbing.
Some times the leaves of the plants are modified variously like Pitcher plants, other
insectivorous plants including sundew, bladderwort and venus-fly-trap worth to study about.
7.
Some other morphological terms of leaf:
Pulvinus: Leaf base swells and forms a cushion like structures.
Stipel: Stipule like out growth from the base of leaflets of a compound leaf.
Heterophylly: occurrence of different types of leaves on the same plant.
Ligule: Membraneous outgrowth located at the junction of the petiole and the leaf
lamina. Mostly seen in the gramineae and the zinziberaceae.
Auricle: Leaf auricle is the winged expansion of hypopodium or the leaf base,
which is continuous with the lamina.
8. Terminologies simplified or other than discussed above
Pulvinus:- Swollen base of the petiole
Petiolate leaves:- Leaves with petiole
Sessile leaves:- leaves without the petioles
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Sheath:- flattened leaf base which clasps or sheaths around the stem
Phyllotaxy:- study of the arrangements of leaves
Alternate / spiral / acyclic:- Leaves are arranged at each nodes in a spiral manner
Opposite:- a pair of leaves are arranged at each nodes opposite to each other
Whorled / verticillate /cyclic:- three or more leaves are arranged at each nodes in a
circular manner
Distichous:- alternate leaves arranged in two vertical rows
Tristichous:- (alternate) leaves arranged in three rows
Pentastichous:- (alternate) leaves arranged in five rows
Octastichous:- (alternate) leaves arranged in eight rows
Parastichous:- (alternate leaves) arranged in more then eight rows
Opposite decussate:- pair of opposite leaves, but each pair is at right angle to the pair
above and below it
Opposite superposed:- pair of leaves; each pair directly placed over the other
Simple leaf:- leaves with single leaf blade, may have incision but not to the midrib or
petiole
Compound leaf:- (segmented leaf blade)leaves with leaflets, incision up to the midrib
(rachis) or petiole,
Pinnate:- leaflets arranged in two ranks on the opposite sides of the rachis
Palmate:- leaves having more then five or more lobes
Unipinnate:- compound leaves in which the leaflets are arranged in the rachis or midrib
Imparipinnate:- type of unipinnate leaves in which the terminal end of the rachis bears
a leaflet
Paripinnate:- unipinnate leaves in which the end of the rachis bears a pair of leaflets
Bipinnate:- leaves with secondary (branches) rachis bearing the leaflets
Tripinnate:- rachis are branched twice bearing the leaflets
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Decompound:- Leaves in which the rachis are branched more then twice (i.e. pinnately
thrice)
Unifoliate:- Single leaflet articulated to the apex of the petiole
Bifoliate:- Two leaflets articulated at the apex of petiole
Trifoliate:- three leaflets articulated at the apex of petiole
Quadrifoliate:- four leaflets articulated at the apex of petiole
Digitate / Multifoliate:- more then five leaflets articulated at the apex of the petiole
Reticulate:- veins arranged intricately forming a network
Parallel:- veins run parallel or almost parallel to each other
Unicostate / pinnate type:- leaves with one strong midrib or main rib
Multicostate / Palmate type:- more then one strong mid rib
Multicostate convergent:- more then one midrib arise from the tip of petiole and meet
at the apex of the lamina
Multicostate divergent:- more then one midrib arise and move out wards (diverge)
from the petiole apex
Peltate leaf:- petiole attached to the back of the lamina and is at right angle.
9.
Phyllotaxy: The arrangement of leaf: They are of following kinds:
Alternate
A single leaf at the node
Opposite
Two leaves at the node, each usually subtending (immediately
below and close to) a lateral bud or shoot
Whorled/ verticillate More than two leaves at the node
Rank - when applied to leaves, denotes rows of leaves along the shoot
Decussate - four ranked or opposite leaves alternating at right angles to those
above and below
Cauline - leaves are those associated with the central shoot
Fascicled - closely clustered or grouped .
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Cauline
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Fasicicled.
FLOWERS AND INFLORESCENCE
Flowers:
These are the specialized shoots of the flowering plants where the foliage leaves are
modified into different floral leaves.
A flower consists of the following major parts (whorls):
Calyx
Corolla
Androecium and
Gynoecium.
Calyx:
This is the first accessary whorl of the floral part. The respective or
individual leaves of the calyx are called as sepals. These sepals remain either
united or free. If they are found united the sepals are called as gamosepalous
and if they are free they are called as polysepalous. Sepals are generally
green in colour and are sessile (stalk less).
Pappus is the hairy/scaly/feather like modified calyx. Some other
modifications are hood (enlarged sepals) and spur (prolonged tubular beak
like structure). When the calyx falls off at the same time with corolla, after
fertilization than it becomes deciduous, and persistent if the calyx is
permanently attached with the fruits.
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Function :-
protection,
acts as flag apparatus (i.e. attracts insects),
when green carries out photosynthesis.
Cohesion of sepals:
Polysepalous:-Sepals are free from each other as in Mustard
Gamosepalous:-Sepals are fused with each other as in China rose.
Duration of sepals:
Caducous:-Sepals fall of as soon as the floral buds open as in poppy.
Deciduous:-Sepals fall off when the flowers wither as in Brassica.
Persistent:-Sepals remain attached with the fruits as in Solanum.
Corolla:
This is the second accessary whorl of the flower. The individual members of
this whorl are called as petals. They are generally coloured and rarely green.
When the petals are united they are called as gamopetalous and when they
are free they are called as polypetalous. Sometimes the petals are stalked,
the stalks are called claw(s) and the expanded lobes, limbs. Some times the
corolla is spurred (spur is present) and saccate (sac like or pouch like
structure present at the base).
Function:
-Function of flag apparatus,
-secretes nectar in some cases,
-protection of the essential whorls.
Cohesion of petals:Polypetalous:-Petals are free from each other as in mustard.
Gamopetalous:-Petals are united with each other as in Datura .
Shape of corolla:Polypelaous:Cruciferous:-Four, free, clawed petals arranged in the form of a cross
as in mustard.
Caryophyllaceous:-This is formed by five free petals with long
claws. The limbs of petals are placed at right angle to
the claws as in Dianthus.
Rosaceous:-Five petals with very short claws and limbs spread
outwardly as in wild rose.
Gamopetalous:Campunulate:-Petals forming bell shaped structure as in Campanula.
Tubular:-Petals forming tube like structure as in Datura.
Rotate:-Corolla is more or less wheelshaped in appearance as in
Ixora.
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Urecolate:-Corolla tube is swollen in the middle tapering towards
both base and apex as in Barophylum.
Ligulate:-Five petals united to form a short tube at the base, which
split on one side and becomes flattened like a strap
above as in the family Compositae.
Papilionaceous:-Five petals free and are so arranged as to resemble a
butterfly .It consists of an outer most ,the largest
vexillium or standard, two lateral or wings and two
anterior fused petals ,the keel as in sweet pea.
Biliabate/two-lipped:-Corolla gamopetalous ,limb of the corolla is
divided into two lips,the upper and the lower with the
mouth wide open as in Ocimum.
Bilibate personate:-Corolla gamapetalous and two lipped and the
lips are placed so near that they close the mouth of the
corolla.The projection of the lower lip.which closes the
mouth of the corolla tube ,is called as palate as in
Antirrinum.
Aestivation of corolla and calyx:
It is the arrangement of floral whorls i.e calyx and corolla. It is of
following types:
Valvate:-The floral leaves, either corolla or calyx are in contact with
each other by their margin only without overlapping as in
Calatropis.
Twisted:-one member of the floral whorls overlaps the next one as in
China rose.
Imbricate:-Out of four members ,one is completely internal being
overlapped by the adjacent members.The other three are
partially internal and partially external as in Cassia.
Vexillary:-Out of five members, one which faces the mother axis
(the posterior one ) is the largest and covers the two
lateral members which in turn covers the innermost two
smallest members as in pea.
Androecium:
The third member or the whorl of the flower. The individual members are
known as stamens. Stamen consists of slender stalk called as filament
which bears at the apex two anther lobes. When the filament is absent than
the stamen is called as sessile. The two anther lobes are connected by
connective tissue. Each anther lobe has two pollen chambers Known as
pollen sacs. The pollen sacs contain the pollen grains.
When the stamens are arranged in two whorls, if the stamens on the outer
whorl are shorter as compared to the inner ones,this arrangement becomes
tetradynamous. In case of didynamous 4 stamens are arranged in a single
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whorl but either the posterior or the anterior stamens are shorter. It is
heterodynamous if the length of the stamens are different. When the
stamens are adnate (joined) to the corolla or petals than this situation is
epipetalous. Adhesion between stamens and carpels as gynandrous.
Stamens are sometimes seen united by their filaments. These unions are of
the following types:
Monadelphous: All the stamens are united by their filaments but the
anthers remain free.
Diadelphous: 9 out of 10 stamens are united by their filaments and
the posterior one is free. Polyadelphous: number of filaments join
together to form a number of bundles.
At times they are also joined by their anther rather than the filaments. this
condition is called as syngenecious. And when ever the stamens are found
united by filaments as well as anthers, than it is called as synandrous.
Function:
-Production of pollen grains.
Adhesion of stamen:-Unison of stamen with other members viz; petals ,perianth
leaves ,gynoecium’s etc.It is of following types:
Epipetalous:-When the satem are fused with petals as in Petunia.
Epiphylous:-When ths stamen are fused with preianth as in
Asphodelus.
Gynandrous:-Whwn the satem are fused with gynoecium as in
Calotropis.
Length of stamen:
Didynamous:-Whwn out of four stamen,two are small and other two
are long as in Ocimum.
Tetradynamous:-When out of six stamen ,the inner four are longer
than the outer two stamen as in Mustrad.
Number of stamen:
Monodrous:-Flowers with one stamen as in Euphorbia.
Diandrous:-Flowers with two stamen as in Coronopus.
Triandrous:-Flowers with three stamen.
Tetrandrous:-Flowers having four stamen.
Polyandrous:-Flowers with numerous free stamens.
Attachment of anther to the filaments:
Basifixed:-Filaments are attached to the base of the lobes as in
Brasica.
Dorsifixed:-Filaments are attached to the dorsal side of the anther
ie.to the back of the anther as in Bauhinia.
Adnate:-When the filaments runs up form base to the apex
ie.throughout the length of the anther as in Michelia.
Versatile:-Filkaments is attached to the back of the anther at a single
point only so that it can swing freely in the air as in
Many grasses.
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Dehiscence of anther;
Introse:-Dehiscence take place towards the inner side of the flowers
as in Stellaria.
Extrose:-Dehiscenmce takes place towards the outer side of the
periphery of the flowers as in Rununculus.
Number of anther lobes:
Monothecous:-When there is only one anther lobe as in Malva.
Dithecous:-When there are two anther lobes as in Argemone.
Gynoecium or Pistil:
This is the topmost or the centrally placed essential floral whorl. The
individual members are called as carpels. Carpel consists of a swollen basal
structure, ovary. The long filiform structure above the ovary is style and the
tip of the style as stigma.
Function:
-Production of megaspore, fruits and seeds.
Number of carpels:Monocarpellary:-Flowers with one carpel as in Cajanus.
Bicarpellary:-Flowers with two carpels
Tricarpellary:-Flowers with three carpels as in Stellaria.
Tetracarpellary:-flowers with four carpels as in Datura.
Pentacarpellary:-Flowers with five carpels as in Melia.
Multicarpellary:-Flowers with numerous carpels as in hibiscus.
Cohesion of carpels:
Apocarpus:-When gynoecium consists of more than one carpel and they are
freeas in Ranunculus.
Syncarpous:-With more than one carpel and they are fused.
Position of carpels:
Hypogynous, perigynous and epigynous:
Pistil is at the highest level as compared to the other whorls i.e. other whorls
are arranged below the pistil. This type of flower is hypogynous. In this case
the ovary is superior. When the flat pistil is surrounded by stamens, petals
and sepals successively, than this condition is called as perigynous. And in
case of epigynous flowers the other floral whorls are arranged above the
ovary i.e. ovary is inferior
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OVARY POSITION
Locules in the ovary: Depending upon the number of locules ,the ovary can be:
Unilocular:-With one locule
Bilocular:-Two locules.
Trilocular:-Three locules.
Multilocular:-with many locules.
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Placentation:
Marginal :-Unilocular ovary and placenta developes along the ventral suture as in pea.
Axil:-Ovary many chambered ,syncarpous but oner chambered and placenta developes
from central axis as in China rose.
Central:-Ovary multicarpellary ,syncarpousbut one chambered and placenta developes
from the central axis as in Dianthus.
Parietal:-Ovary multicarpellary,syncarpous but one chambered and placenta arises
from the inner wall of the ovary as in Poppy.
Basal:-Ovary monocarpellary with one locule and placenta develops at the base of the
ovary as in sunflower.
Superficial:-Ovary polycarpellary,syncarpousand with many locules and the placenta
developes all around the inner surface of the oartition wall as in water lilly.
Stigma: It is the apical end of the style and it is following kinds:
Plumose:-Feather like.
Discoid:-Disc shaped.
Bifid:-Divided into two
Capitate;-Knobe like.
Inflorescence:
This is the branch (system) which bears flowers. Or the arrangement of flowers on the floral
axis and is a branch system.
The stalk of the inflorescence is the peduncle. Rachis is the floral axis and the stalks of the
individual flowers are pedicel. Flowers with the pedicels are called as pedicellate and with
out pedicels are sessile.
When the rachis is condensed to a flat or short, fleshy and dilated structure it is called as
receptacle. Scape is the inflorescence axis developing from the under ground stem. The
small rachis of gramineae i.e. grass inflorescence produced beyond the flower is rachilla.
Inflorescences are mainly of three types:
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-Racemose or indefinite inflorescence
-Cymose or definite inflorescence and
-Mixed inflorescence.
Racemose or indefinite type:
In this case the primary floral axis i.e. rachis is never terminated in flower. The rachis
continues to grow giving flowers laterally in acropetal succession i.e. the oldest flowers are
near the base and the youngest towards the apex. The racemose inflorescence consists of the
following types:
Raceme:
Long primary rachis bearing pedicellate flowers opening in acropetal order e.g.
Brassica,Orchids etc.
Corymb:
A typical raceme with unequal flower stalks e.g. Prunus cerasus.
Spike:
Similar to raceme but the flowers are sessile e.g. Aerva aspera.
Catkin:
It is a spike of unisexual flowers with weak drooping peduncle which ultimately
breaks off from the parent plants e.g. Salix sp.
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Spadix:
It is a modified spike with a fleshy rachis and large bract (spathe) covering the
inflorescence e.g. Colocasia.
Spikelet / Locusta:
This is a condensed spike subtending one or few flowers. Bracts are termed as
glumes. The rachilla may be small and short or long. The first two glumes are
empty. Found in gramineae family which will be dealt in detail in taxonomy.
Strobile:
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It is a modified spike, consisting of persistent membraneous bracts or scales bearing
pistillate flower at each axil.
Panicle:
It is a compound raceme. The branches of the primary axis bear the flowers.
Umbel:
This inflorescence has a short floral axis upon which pedicellate flowers are
arranged in a radiating manner on short floral axis.
Capitulum / head:
The rachis is called receptacle which is fleshy and dilated. The flowers are sessile. In
some cases the marginal flowers are ligulate, female or sterile, and are known as ray
florets. The centrally located flowers are bisexual and are called as disc florets. E.g.
Helianthus.
Other types found in this category of inflorescence are compound corymb (Panicled
corymb), compound spike, compound umbel and compound spadix.
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Cymose or definite inflorescence:
Here the growth of the primary axis is checked and there by terminated by a flower. the
young flowers occur below it. Flowers are there fore, basipetal. This inflorescence consists
of the following types:
Solitary terminal or Axillary flower:
The axis is terminated by a single flower. e.g. Hibiscus.
Monochasium / Uniparous cyme:
The primary axis ends in a flower and one lateral branch is produced ending in a
flower which repeats the processes.It consists of:
Helicoid cyme
Scorpioid cyme.
Dichasium or biparous cyme:
The primary axis terminates in a flower. This axis, below the flower produces two
lateral branches terminating in flowers. These branches in turn produces lateral
branches bearing flowers. The processes is repeated e.g. Jasminium.
Polychasium or multiparous cyme:
This type of inflorescence results when the primary axis terminates in a flower and
produces beyond the apex more then two axis in whorled manner. E.g. Viburnum
sp.
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Other special type of condensed cymose inflorescence are Cythium (e.g. Euphorbia
sp.), Verticillaster (compound biparous cyme as seen in labiatae), Hypanthium etc.
Cythium:-Modified cymose inflorescence as in Euphorbia etc.
Verticillaster:-Condensed form of cymose. Ie.Ocimum,mint etc.
Hypanthium:- Specialised form of racemose .i.e.Fig.
Mixed inflorescence:
This type of inflorescence consists of combination of raceme+raceme or raceme+cymose or
cymose to cymose or any other combinations. E.g. Mixed spadix found in banana, Musa
paradisiaca consists of cymosely arranged flower groups. These flowers are racemosely
arranged on the primary axis
Some terminologies of flower:
Complete or incomplete flowers:
Those Flowers which have all the four floral whorls are complete flowers and those
flowers which do not have all the floral whorls are rendered as incomplete flowers.
Regular and irregular flowers:
The flower is said to be regular or actinomorphic when it can be cut into two equal
halves through any plane. The flowers also have more or less equal sized petals,
sepals stamens etc. The flower is irregular or (symmetrically) zygomorphic when
the sepals, petals etc. are not equal and the flower cannot be cut in to two equal
halves through any plane except one.
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How ever there are still some exceptions in which the flowers cannot be cut into two
equal halves through any planes, such flowers are termed as asymmetrically
zygomorphic.
COROLLA SHAPES
ACTINOMORPHIC
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ZYGOMORPHIC
Bisexual and unisexual flowers:
The flower is bisexual or hermaphrodite when it has both the male (androecium)
and female (gynoecium) parts. The flower becomes unisexual when either
gynoecium or androecium is present. Unisexual Flowers can be:
Staminate:-With only male organe
Pistilate:- With only female organe.
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Cyclic and acyclic flowers:
A flower is said to be cyclic when the sepals, petals, carpels and stamens are
arranged in whorls or in circle. If the floral leaves are arranged in spiral or non
circular manner than it becomes acyclic flower.
Neuter or nude flower:
Both androecium and gynoecium are absent in case of neuter flower. Where as in
case of nude flower either androecium, gynoecium or both are present but calyx and
corolla are absent.
Pistillate and staminate flowers:
unisexual male flowers are staminate and unisexual female flowers are pistillate.
Dioecious, monoecious and polygamous:
Plants bearing either male or female flowers only are dioecious. Plants bearing
unisexual flowers of both the sexes are monoecious and when plants bear unisexual
flowers of both the sexes in addition to the bisexual flowers they are polygamous.
Perianth and tapels:
Calyx and corolla together is termed as perianth. Specially applied when either
corolla only or calyx only are present in a flower. When the sepals and petals are
similar to each other in coloration, size, forms etc. the components are called as
tapels.
Thalamus and Disc:
Thalamus is the axis of the flower where as disc is the modification or an out
growth of thalamus.
Achlamydous and Monochlamydous:
Achlamydous:-When the flowers have neither calyx nor corolla, such flowers are
also called naked flowers.
Monochlamydous:-When the flowers have only one accessory whorl .ie. Either
calyx or corolla or perianth.
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Bracts:
These are the specialised leaves form the axils of which flowers arise. They
are of following types:
Foliocious:-Green, flat and leaf-like as in Adhatoda spp.
Spathe:-Large, boat shaped bract enclosing a group of flowers as in Musa.
Petaliod:-Brightly coloured, looking like petals as in Euphobia.
Involucre:-Numerous bract arranged in one or more whorls around the cluster of
flowers as in Helianthus.
Scaly:-Small and membranous bract.
Epicalyx:-One or more whorls of bracteoles at the base of calyx as in China rose.
Glumes:-Small dry bract as in wheat and rice.
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