Download PLANT morphology

PLANT
MORPHOLOGY
Morphology:
branch of botany that deals with external features
of plants.
Anatomy:
also known as Micro morphology of plants and plant
or vegetable histology; is concerned with the
microscopic structure of the tissues, cells and organs
of plants.
Taxonomy:
the classification and naming of plants.
The Leaves
Phyllotaxis (arrangement of cauline leaves):
Alternate (spiral or acyclic): one leaf arises at each node and the
leaves are not shaded each other.
Opposite: they may be;
Opposite decussate: one pair of leaves is perpendicular to the other.
Opposite superposed: each pair of leaves is parallel to the other.
Whorled: more than two leaves arise at each node e.g. Nerium.
Parts of leaves:
The leaf consists of leaf base, stipules, stalk or petiole and blade
or lamina.
1- Leaf base:
It is the part of the leaf directly attached to the stem.
2- Stipules:
they are appendages at the leaf base, when they are absent the
leaf is exstipulate. e.g. tendrillar, spiny, hairy.
3- Petiole:
it is the part of the leaf between the blade and the base,
it has vascular tissue. When it is absent the leaf is sessile.
4- Leaf blade or lamina:
It is the green flattened part of the leaf used for photosynthesis,
it may be:
Simple: when the blade is continuous.
Lobed: when the blade divides into number of lobes
connected by undivided center.
Compound: when the blade is divided into independent
leaflets.
A- Forms of simple
leaves or leaflets:
B- Forms of lobed leaves
1- Pinnately lobed:
divisions directed towards the midrib;
a- Pinnatifid: the cutting is less than half distance between margin and
midrib.
b- Pinnatipartite: the cutting is more than half the distance between
margin and midrib.
c- Pinnatisect: the cuttings reach the midrib.
C- Forms of compound leaves
a-Compound pinnate:
the leaflets are arranged in two rows on leaf stalk.
Paripinnate: ends by two leaflets.
Imparipinnate: ends by one leaflet.
b- Compound palmate: more than two leaflets are radiated from the
tip of petiole.
Leaf margin
Serrate: with small teeth directed forwards.
Serrulate: minutely serrate.
Dentate: teeth directed outwards.
Crenate: teeth rounded.
Spiny: margin with spiny processes.
Entire: the margin has no processes.
Leaf apex
Acute: tip forming acute angle.
Acuminate: tip is narrow and prolonged.
Obtuse: rounded tip.
Truncate: tip is flat.
Emarginate: deeply notched.
Mucronate: tip with short horny point.
Leaf surface
Glabrous: smooth surface.
Hairy: with coarse hairs.
Wrinkled .Rough .Waxy .
Base of lamina
Symmetric: the two halves of the lamina are identical.
Asymmetric: the two halves of the lamina are not identical.
Decurrent.
Venation
1- Reticulate: the veins forms network;
a- Reticulate pinnate: with single midrib from which branches are
given.
b- Reticulate palmate: with several veins.
2- Parallel: the veins are parallel and of same size.
Comparison between compound leaf and branch
Compound leaf
Branch
1- It arises directly at the node of stem and not
subtended from outside by any structure.
1- It is axillary to the leaf.
2- The rachis bearing the leaflets is not divided to
nodes or internodes.
2- The branch divides to nodes and internodes and
bearing leaves at the nodes.
3- There is no axillary buds in the axil of leaflets
and no terminal bud at the end of rachis
3- A branch bears axillary buds in the axils of
leaves
and terminal bud at its apex.
4- The stipules are borne at base of compound
leaf, no stipules in base of leaflets.
4- The leaves of branch bear stipules at their
bases.
5- The leaflets of compound leaf fall off
simultaneously.
5- The leaves of branch fall off at different times.
The Flower
The flower:
is a modified fertile shoot, carrying modified leaves, highly
specialized for performance of reproductive function and adapted to
produce fruits and seeds, i.e. for the propagation of the individual.
A typical flower:
is usually formed of four sets of floral leaves arranged on a
shortened axis (flower stalk or pedicel), the swollen or expanded
apex of which is called receptacle.
The floral leaves are in the following sequence from the periphery to the center
The calyx: composed of sepals.
The corolla: composed of petals.
The petals and sepals when all alike called perianth.
The andrœcium (male organ): composed of stamens; each stamen composed of
anther and filament).
The gynæcium (pistil, female organ): composed of carpels; each carpel composed
of ovary, style and stigma.
Parts of a Flower
The ovary may be inserted on the receptacle on a level above all the
other parts; so the ovary is known as superior and the flower is
hypogenous.
The ovary may be inserted on the receptacle on a level below all the
other parts; so the ovary is known as inferior and the flower is
epigenous.
Kinds of Flowers
1- According to the number of whorls.
Tetracyclic: showing four whorls e.g.Iridaceae.
Pentacyclic: with five whorls.
2- According to the number of segments in each whorl.
Bimerous: with two segments e.g. Cruciferae.
Trimerous: with three segments in each whorl as in Monocots.
Pentamerous: with five segments as in Dicots.
3- According to the presence of all floral parts.
Complete: the flower has all the usual parts.
Incomplete: if lacking one or some of the regular parts.
4- According to the symmetry of all floral leaves.
Regular or actinomorphic (Ө): when the segments in each whorl are all alike, regularly
arranged and the flower can be divided by a number of radial longitudinal cuts into
equal halves e.g. Clove.
Irregular: when the members of one or more whorls are not all alike. In such case the
flower may be:
Zygomorphic (%): when it can be divided only in one plane into equal halves as in
Papilionoideae.
5- According to presence or absence of sexual organs.
Hermaphrodite, bisexual or perfect: when both male and female organs are present
e.g. Rosa.
Sterile or neutral:
when both male and female organs are absent or not functioning e.g. the marginal
florets of Sunflower.
Unisexual or imperfect: when only one of the sexual organs is present and
functioning.
These flowers are either:
Staminate (♂): which possess only the male organs.
Pistillate (♀) : which possess only the female organs.
Bract: is leafy
structure from its
arises a flower.
Involucre: is a
group of bracts
arranged in one
or more whorls
just below the
flower e.g.
Nigella or group
of flowers e.g.
Compositae.
The flower may
be accompanied
by accessory leafy
structures:
Bracteole:
is a scalelike leaf
found on
the floral
stalk.
The Seeds
Definition: Mature fertilized ovule which has one
scar (hilum) representing the point of attachment
to its stalk (funicle).
.
Structure of the seed
It consists of seed coat, embryo and endosperm
1- Seed coat:
Testa:
the testa may be leathery e.g. Vicia faba, sculptured e.g. Ricinus,
or membranous e.g. Arachis.
Hilum:
It is the point of attachment of the seed to funicle.
The micopyle:
It is formed due to incomplete fusion of integuments of ovule
Function of micropyle:
acts for absorption of water during seed germination.
allows the pollen tube to enter to embryo sac.
2- Embryo:
The embryo axis: it is the elongated portion of embryo consisting
of short hypocotyls, at one end of which there is the plumule and
at the other is the radicle.
The plumule:
It is the upper part of the embryo axis and is the first bud. It gives
the shoot system.
It does not differentiate to nodes and internodes.
The epicotyl is the portion of the plumule above the cotyledonary
stalk.
The radicle:
It is the lower portion of the embryo axis which divides to give the
primary root.
Cotyledons (seed leaves): the plant with one cotyledon are
known as monocots e.g. Zea, while those with two cotyledons are
dicots e.g. Vicia faba.
Functions of cotyledons:
Storage of food in exalbuminous e.g. Vicia or Phaseolus.
Protection of epicotyl and plumule.
May become green and undergo photosynthesis.
3- The storage tissue (endosperm):
Exendospermic (exalbuminous) seeds: they have no endosperm
and the reserve food is stored in the cotyledons e.g. Vicia,
Phaseolus. In this case the embryo is large.
Endospermic (albuminous) seeds: the reserve food is stored in
special tissue called endosperm outside the cotyledons. In this
case the embryo is small.
The endosperm materials may be:
Hemi cellulose e.g. Phoenix (date palm).
Protein e.g. wheat.
Aleurone grains e.g. Ricinus.
The Fruits
Definition:
The fruit: is the whole product of the development of the
gynaecium as a result of fertilization. Sometimes other parts of the
flower in addition to the gynaecium participate in the production
of the fruit.
Types of Friuts
True fruit: fruit is formed from the gynaecium of a single
flower alone.
false fruit: when other parts of the flower take part in its
formation.
composite fruit: If the fruit is formed from the whole
inflorescence and not from a single flower.
Simple Fruits
a- Simple dry dehiscent fruits:
These are where the pericarp becomes dry, this group includes:
i- Legume:
fruit formed from one carpel which splits along both dorsal and ventral
sutures as
senna pods.
ii- Follicle:
fruit formed from one carpel which dehisces by the inner suture only.
iii- Capsule:
fruit is derived from a syncarpous ovary, it is many seeded fruit e.g.
Papaver.
iv- Silique:
fruit from two carpels with a septum in-between, it splits to
expose seed along central membrane (mustards).
b- Simple dry indehiscent fruits:
the pericarp becomes dry and do not split open when ripe.
They include the followingtypes:
i- Achene:
one-seeded fruit formed of one carpel, the pericarp is free from the testa.
ii- Caryopsis or grain: it is an achene in which the pericarp and testa are
fused together as wheat.
iii- Nut: similar to achene but usually bigger, formed of two or three
carpels.
iv- samara: it is winged, one seeded fruit formed of one carpel or of more
carpels
C- Simple dry schizocarpic or splitting fruits
The pericarp becomes dry, they are two to many seeded they split
up into a number of one-seeded indehiscent parts called
mericarps. They include several types but the most familiar type is
cremocarp.
Cremocarp:
formed of two carpels, the ovary is inferior and bilocular, the
cremocarp splits longitudinally between the two locules into two
one-seeded mericarps as in Umbelliferae e.g. anise, Fennel.
d- Simple succulent fruits
i- Drupe: the fruit derived from one or more carpels. The ovary is
superior or inferior unilocular, the epicarp is leathery the mesocarp
is fleshy the endocarp is hard and enclosing a single seed as Olive.
ii- Berry: the fruit is formed from one or more carpels and the
pericarp is entirely fleshy. It is usually many seeded as Orange,
Lemon.
False Fruits
they are derived from mature ovary of a
single flower accompanied by other
parts of the same flower which on
ripening become usually swollen and
fleshy e.g. Apple.
Composite fruits
Strobile: derived from a scaly
inflorescence named strobile, one or
two achenial fruits are present in the
axil of each scale.