Division Angiospermophyta (flowering plants)

1. The sporophyte is well differentiated into roots for anchorage and absorption of water and mineral salts, stem for support and transport and leaves for photosynthesis (i.e. they have chloroplast).
2. They show alternation of generation with the sporophyte being dominant over the gametophyte, i.e. the gametophyte is reduced. Have well developed vascular tissues which consist of xylem with tracheids and vessels for transport of water and mineral salts and support and the phloem has got companion cells and sieve elements.
3. They are heterosporous (microspore/pollen grain and megaspore/embryo)
4. Fertilization does not depend on water because the male gamete is connected to the ovum by the pollen tube formed by germination of pollen grain when it lands on the stigma of the same species.

1. They provide flowers in which megaspores and microspores develop.
2. They undergo double fertilization. After fertilization, ovary develops into fruit and the ovules into seeds which are enclosed in the ovary.
3. Xylem contains vessels and tracheids and phloem has sieve tubes and companion cells.

The angiosperms are divided into two major groups:

1. Monocotyledonae
2. Dicotyledonae

Flowers are reproductive structures in flowering plants (angiosperms) whose evolutionary origin are unclear but sometimes regarded as collection of highly specialized leaves. The flowers are commonly referred to simply as organs of sexual reproduction.

Parts of flower

They are arranged in spiral form in few primitive flowers or in whorls around the upper parts (receptacle) of a flower stalk (pedicel). Some flowers are found as a collection of flowers borne on the same stalk (inflorescence).

Parts

i. Receptacle - Is the end of the flower stalk (pedicel) from which the perianth, gynaecium, and androecium arises.

ii. Perianth - Consists of two whorls of leaf like segments. The whorls are similar in monocot but different in dicot. The outer whorl is called sepal (Calyx) and inner whorl is petal (corolla) Calyx- Is the collection of sepals, they are usually green and leaf like structures that encloses and protect the flower buds.

Corolla- Is a collection of petals. In insects pollinated flowers the petals are usually large and brightly coloured to attract insects.

iii. Androecium - is a collection of stamens forming the male reproductive organ of the flower. This consist of anther and filaments, in anther pollen grain are made. Filaments rises water to the anther.

iv. Gynaecium (Pistil) is the collection carpels forming the female reproductive organs of the flower. This consists of stigma, style and ovary. Stigma receive pollen grain during pollination, style holds in position stigma and ovary contains one or more ovules.

Generalized structure of flower

Symmetry of flowers

If the flower parts are arranged in radial symmetry around the receptacle, the flower is said to be regular or actinomorphic e.g. bluebell. If the flower shows bilateral symmetry only, it is said to be irregular or zygomorphic e.g. pea.

Floral formulae

Is the presentation of floral parts of the flower by using symbols. In floral formulae the following terms are used to describe the following terms are used to describe various parts of the flower.

A. Symmetry of the flower

Actinomorphic/ Radial or regular flower

Zygomorphic/ Bilateral or irregular flower

B. Sex of the Flower

flower – The flower with separate male and female parts

Staminate flower- The flower with male parts only

Pistilate flower – The flower with female parts only

Monoecious flower- The flower with both male and female parts both on the same flower

Hermaphrodite- The flower with male and female parts

C. Flower receptacle

Pedicelate flower – Is the type of flower with pedicel or flower stalk

Sessile flower – Is the type of flower without pedicel or flower stalk

N.B. This is not seen in floral formulae but appears in floral diagrams.

Perianth

Consists of two whorls of the flower which is

K- Calyx followed by the number of sepals. If sepals are free K5 and if sepals are fused K(5)

C- Corolla followed by number of petals. If the petals are free C5 and if sepals are fused C(5).

Male parts of the flower

A- Androecium followed by followed by the number of pollen grains e.g. A5 if fused. A∞ if the number of pollen grains exceed 16.

Female part of the flower

G- Gynaecium followed by the number of carpels eg G1 is free , G(2) if fused. The position of ovary with respect to receptacle

Hypogenous flower/ Inferior ovary

A flower in which ovary is placed highest on the thalamus and the other floral structure underneath. For the example

Diagram of hypogenous

Perigynous flower

A flower in which ovary is at the same plane as other floral structure.

For example G2

Epigynous/ Superior

A flower in which ovary is placed lower to other floral structure on the thalamus

Also flower have first leaf which is known as bracteates; a flower with bract. Ebracteate a flower without a bract.

Symbols of Floral formulae

Actinomorphic flower

Zygomorphic flower

Staminate flower

Pistilate flower

Bisexual flower

Br Bracteate flower

Ebr Ebracteate flower

K Calyx

C Corolla or = androecium born from corolla

G Gynoecium or – androecium born from corolla

A Androecium

Examples of Floral formulae

i. Garden pea Pisum sativum

Floral formulae

ii. Solanum

iii. Hibiscus flower

Floral Diagram

This is the representation of flower parts by using concentric cycles to present various parts of the flower.

• The outer cycle represents the first whorl of the flower which calyx/ sepals
• The second cycle represents the corolla or petals
• The 3rd represents androecium
• The 4th part represent gynaecium

In floral diagram the gynaecium also show the ovary with placentation.

The ovary consists of ovary wall called locule. The ovules are situated on the inner or adaxial (ventral) forms a placenta. In carpel the placenta occurs close to the margin.