RHS Level 2 Certificate

Week 6 – Flowers and Seeds

Learning objectives

1. Parts of the flower1.1 Name the main types of inflorescence found on plants.1.2 Describe the structure of a typical dicotyledonous flower.1.3 State the role of each component of the flower.1.4 Define the terms: ‘monoecious’, ‘dioecious’ and ‘hermaphrodite’.1.5 Describe how petals and sepals are modified to tepals in specific genera.2. Fruits and seeds2.1 Define the term: ‘seed’ and state the role of seeds in plant reproduction.2.2 Define the term ‘fruit’ and state the role of the fruit in plant reproduction. 2.3 State that fruits can be divided into dry types (dehiscent and indehiscent) and

fleshy (succulent ) types (true and false); and that these can be distributed by wind, water, animals (externally), and animals (internally).

2.4 Name one example of each type of fruit listed in 2.3, and one example for each distribution method.

2.5 Describe the internal and external structure of the seed of a monocotyledon (examples to include maize, Zea mays) and a dicotyledon (examples to include French bean, Phaseolus vulgaris and broad bean, Vicia faba).

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Parts of the flower

Female parts

Carpel = Stigma + style + ovary + ovule

Male Parts

Stamen = Anther + filament

External parts

Petal; Sepal; Bract; Pedicel or peduncle

Role of each part of the flower

Male parts – anthers produce pollen which contains ‘sperm’. Supported on the filament.

Female parts – stigma receives pollen, ovules contain ‘eggs’ awaiting fertilization. Stigma supported on stamen

Petals – brightly coloured, ultraviolet sensitive pigments

Sepal – leaf like structure that encloses and protects the flower bud

Bract – modified leaf below flower or inflorescence Tepal – modified leaf that takes the place of petals in

some species e.g. Tulipa sp.

Pollination strategies

Insect pollinated flowers – brightly coloured and large; produce nectar as a lure; pollen contains protein which bees and other insects feed on; scented to attract pollinators.

Wind pollinated – no need to attract pollinators, so no scent, nectar or protein in pollen. Very large amounts of very light pollen.

Many monocots and trees are wind pollinated, but not all. The size and structure of the flower reveals the strategy used.

Different types of flower

Monoecious – separate male and female flowers on the same plant

Dioecious – male and female flowers on different plants

Hermaphrodite – flowers containing male and female organs (which may or may not be self compatible)

Male flower? Female Flower?

Fruits and Seeds

Seed – formed from the mature fertilized ovule and containing the embryo and stored food.

Fruit – A mature ovary. Functions – protection of seed, encourage ingestion, control germination, facilitate seed dispersal.

False fruit – a structure that resembles a fruit but which is not derived from an ovary. E.g. Yew Taxus baccatta, Apple Malus domestica.

Types of fruit

Dry – e.g. Papaver somniferum Fleshy- having juicy flesh formed from the

ovary . E.g. a drupe such as Prunus x domestica ‘Victoria’

Indehiscent – the pericarp does not split open to release the seeds. E.g. Quercus robur (English Oak).

Dehiscent – the pericarp splits to release the seeds e.g., Lathyrus odoratus (Sweet Pea)

Types of Fruit

Simple Aggregate Multiple

Structure of seeds

Testa – coat Cotyledon – seed leaf Plumule – first shoot Radicle – first root Hypocotyl – first stem

below the seed leaves Micropyle – small hole

where seed joined plant. Dicots and monocot

differences. Monocots have endosperm, dicots generally do not.

Seed dispersal –method and examples

Dry fruit – dispersed by wind Taraxacum officinale (Dandelion)

Fleshy fruit – dispersed by birds (internally) Sorbus acuparia (Mountain Ash)

Indeheiscent fruit – dispersed by animals Quercus robur (English Oak) by squirrels.

Deheiscent fruit – dispersed by water Impatiens glandulifera (Himalayan Balsam)

Learning outcomes

1. Parts of the flower1.1 Name the main types of inflorescence found on plants.1.2 Describe the structure of a typical dicotyledonous flower.1.3 State the role of each component of the flower.1.4 Define the terms: ‘monoecious’, ‘dioecious’ and ‘hermaphrodite’.1.5 Describe how petals and sepals are modified to tepals in specific genera.2. Fruits and seeds2.1 Define the term: ‘seed’ and state the role of seeds in plant reproduction.2.2 Define the term ‘fruit’ and state the role of the fruit in plant reproduction. 2.3 State that fruits can be divided into dry types (dehiscent and indehiscent) and

fleshy (succulent ) types (true and false); and that these can be distributed by wind, water, animals (externally), and animals (internally).

2.4 Name one example of each type of fruit listed in 2.3, and one example for each distribution method.

2.5 Describe the internal and external structure of the seed of a monocotyledon (examples to include maize, Zea mays) and a dicotyledon (examples to include French bean, Phaseolus vulgaris and broad bean, Vicia faba).