Lorraine Kuun, July 2011. The stamens are the male organs and produce pollen that contain the male...

Lorraine Kuun, July 2011

The stamens are the male organs and produce pollen that contain the male gametes

The pistil with the stigma, style and ovary is the female organ of the plant. The ovulums are found in the ovule.


Stamens consist of an anther with a filament.

The anther produces pollen in the pollen sac.

The pollen grains contain the male gametes.


1. Self pollination 2. Geitonogamy 3.Cross-pollination


Most pollinators are insects e.g. Bees, moths, butterflies, beetles.

Some vertebrates also pollinate flowers e.g. Bats, mice, birds (mainly).

Many flowers are pollinated by wind.


Bright colours (bees cannot see red), white for night pollinators e.g. moths

Often sweet scent (attracts moths and butterflies)

Reward of nectar and pollen Contrasting markings on petals to locate

centre of flower (usually not visible to human eye – ultraviolet)

Pollen cling to hair on insect bodies



Landing platform

Nectar guides

Tubular shape, contains nectar

Stamens form “lever”

Pistil overhanging landing platform

Bees attracted to blue and yellow flowers

High yield of dilute nectar Bigger than most insect-pollinated flowers Open in daytime, often red Sturdy against rough feeding of birds Little or no scent – birds have poor sense of

smell Protect ovary against beaks by being

inferior or by partition Pollen sticks together in clumps Often erect or with landing platform for

birds that do not hover



Bright colours

Nectaries

Sturdy landing platform

Stigma close to pollen

Stamens fused in tube to fit beak

Flowers do not have scent, nectar or brightly coloured petals – no need to attract pollinators.

Flowers high on plant to be exposed to wind. Flowers usually small and reduced, lacking

calyx or corolla (sepals and petals). Anthers large and well-exposed. Masses of light, non-sticky pollen produced. Stigmas long and feathery with large area

for trapping pollen.


Meiosis occurs in the pollen grain.

The male gametes are haploid.

When the ripe pollen grain lands on a receptive stigma, it will germinate.

The pollen grain germinates and form a pollen tube.


The ovary contains the ovule(s) with female gametes (n).

The pollen tube grows down the style, through the micropyle and into the embryo sac.

Double fertilisation occurs.


The fruit develops from the following layers:

• Fruit wall from ovary wall.

• Seed from ovule.


A seed consists of a

1. Seed coat – outer layer of ovule (pericarp).

2. Embryo – from fertilisized egg cell (zygote undergoes mitosis).


Endosperm – result of double fertilization. Endosperm is food for embryo – also why we eat seeds for food.


The cotyledons contain food for the embryo in some seeds.

In beans the cotyledons are responsible for photosynthesis after germination before first leaves are formed.


MONOCOTYLEDON


DICOTYLEDON


Resistant to unfavourable conditions as they have seed coat.

Can be dispersed effectively (see later). Can remain viable in dormant state for long

periods. Seeds have stored food reserve in

endosperm or cotyledons; includes starch, oils and or protein.

Important to man as they are cheap form of plant propagation, way to store plants and are a store of food.


Dormancy is a state of rest. Embryo inactive, seed will not germinate.

Some plants have obligatory period of dormancy – seed will not germinate even if conditions are favourable.

Dormancy prevents seeds from hatching in wrong season when seedlings would be exposed to unfavourable conditions. Allows seeds to survive unfavourable conditions.

Allows for seed dispersal agents to act.


Wind – seeds are light with plumes or wings.

Animals – hooks and thorns – cling to wool, stick in paws.

Animals – edible fruit – seeds egested in different position.

Water – seeds contain oil or air bubbles – float away.

Self-dispersed – fruit dry, dehiscent.


COCO DE MER drifts along ocean currents


Most important plant source of food for humans.

Practical form of food – easy to transport and store for long periods of time.

Grains – wheat, maize (mealies), sorghum, rice, oats; mainly starch

Pulses (legumes) – beans, peas, soy beans, peanuts, lentils, plant proteins

Nuts – oily seeds in hard shells e.g. walnuts, cashews, pecans etc.


Many plant species under threat. Seed bank stores seeds of wild plants and crops. UK – conserves seeds of about 10% of wild plant

species at Kew – Millennium Seed Bank Project. Swedish International Seed Vault – reinforced

concrete tunnel – 4,5 million seed samples – will remain viable for 1000’s of years.

MSBP working with SA National Biodiversity Institute – contributing 2500 indigenous species – endangered, endemic, over-exploited


Offer protection against loss of species in wild due to:

1.Habitat loss – agriculture, development of cities, building of dams, large-scale ecological disasters etc.

2.Climate change3.Over-exploitation of certain species


Can be used to 1. re-establish damaged, lost

habitats and ecosystems2. re-introduce extinct,

endangered or threatened species

3. provide research material


Lorraine Kuun, July 2011. The stamens are the male organs and produce pollen that contain the male...

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