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

Branch Compound leaf

1- It is axillary to the leaf . 1 -It arises directly at the node of stem and not subtended from outside by any structure .

2- The branch divides to nodes and internodes and bearing leaves at the nodes .

2 -The rachis bearing the leaflets is not divided to nodes or internodes .

3- A branch bears axillary buds in the axils of leaves

and terminal bud at its apex .

3- There is no axillary buds in the axil of leaflets and no terminal bud at the end of rachis

4- The leaves of branch bear stipules at their bases. 4- The stipules are borne at base of compound leaf, no stipules in base of leaflets.

5- The leaves of branch fall off at different times. 5- The leaflets of compound leaf fall off simultaneously.

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.

The flower may be accompanied by accessory leafy

structures:

Bract: is leafy structure from its arises a flower .

Bracteole: is a scale-like leaf found on the

floral stalk.

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 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.

Fruits

True Fruit

Simple Fruits

Succulent

Dry Schizocarpic

dry indehiscent

dry dehiscent

Aggregate Fruits

False Fruit

Composite Fruit

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.

Types of Friuts

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.

Simple Fruits

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.