Botany

Morphology: branch of botany that deals with external features of plants. Anatomy: also known as Micromorphology 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.

PLANT MORPHOLOGY

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.

* It protects the lateral bud and facilitates the movement of petiole 1- Leaf base: * It is the part of the leaf directly attached to the stem. * It protects the lateral bud and facilitates the movement of petiole

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- Pamatisect: the cuttings reach the base. 2- Palmately lobed: divisions directed towards the base; a- Palmatifid: the cutting is less than half distance between margin and base. b- Palmatipartite: the cutting is more than half the distance between margin and base. c- Pamatisect: the cuttings reach the base.

C- Forms of compound leaves a-Compound pinnate: the leaflets are arranged in two rows on leaf stalk. i- Paripinnate: ends by two leaflets. ii- Imparipinnate: ends by one leaflet. b- Compound palmate: more than two leaflets are radiated from the tip of petiole.

Leaf margin Entire: the margin has no processes. Serrate: with small teeth directed forwards. Serrulate: minutely serrate. Dentate: teeth directed outwards. Crenate: teeth rounded. Spiny: margin with spiny 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. Rough. Waxy. Wrinkled.

Base of lamina 1- Symmetric: the two halves of the lamina are identical. 2- Asymmetric: the two halves of the lamina are not identical. 3- 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 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 Stamen Pistil Ovule Petals Sepals Receptacle Pedicel Stigma Anther Stamen Style Pistil Filament Ovary Ovule Print off a copy of the this flower, white-out the labels and have the students label the parts as you present them in the slide show. Petals Sepals Swollen base where are parts attach Receptacle Pedicel Courtesy of McGraw Hill Publishers

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.

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.

Kinds of Flowers

1- According to the number of whorls i- Tetracyclic: showing four whorls e.g.Iridaceae. ii- Pentacyclic: with five whorls.

2- According to the number of segments in each whorl i- Bimerous: with two segments e.g. Cruciferae. ii- Trimerous: with three segments in each whorl as in Monocots. iii- Pentamerous: with five segments as in Dicots.

3- According to the presence of all floral parts i- Complete: the flower has all the usual parts. ii- Incomplete: if lacking one or some of the regular parts.

4- According to the symmetry of all floral leaves i- 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.

ii- 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 i- Hermaphrodite, bisexual or perfect: when both male and female organs are present e.g. Rosa. ii- Sterile or neutral: when both male and female organs are absent or not functioning e.g. the marginal florets of Sunflower. iii- 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.