Reproductive Strategies Plants. Plant Reproduction Reproduction in Flowering Plants and Conifers The process of pollination The reproductive cells in.

Reproductive Strategies

Plants

Plant Reproduction

•Reproduction in Flowering Plants and Conifers

•The process of pollination•The reproductive cells in these plants are the eggs and pollen produced at particular times of the year.•The eggs remain on the plants. The pollen is transferred to the egg.

Strategies to ensure pollen transfer

• Because plants are fixed in one location they have evolved strategies to ensure their pollen grains are transferred.

• Pollen may be transferred by the following means;– Insects (beetles, flies, bees, butterflies)– Birds of many species– Mammals (bats, small rodents, honey possums)

Strategies to ensure pollen transfer

• Wind pollination– Pollen of all conifers and some flowering plants is

carried by the wind– Pollen carried by the wind is small, smooth and

very light– Flowering plants that are wind pollinated • Do not have brightly coloured flowers• Have pollen producing organs (stamens) exposed to

the wind• Have feathery stigmas to catch passing pollen grains

– Wind pollination is affected by climate

Strategies to ensure pollen transfer

• Most flowering plants are pollinated by insects, birds or mammals– Animals that are the carriers of pollen are called

vectors– Flowering plants attract and reward their vectors

Which vector?• Insect-pollinated flowers–Blue or purple or yellow as these

colours are visible to insects–May have a platform shape for

landing–May have a scent to mimic something

to attract an insect. Eg rotting meat

Which vector?• Insect-pollinated flowers–Usually have nectaries inside the flower

producing sugar-rich nectar attracting insects–Often have ultraviolet reflecting white or

yellow dots or lines to signal the presence of flowers (insects can see UV radiation)

Which vector?Insect-pollinated flowers

Stamens are often arranged to that insects must push through them to reach the nectaries

The pollen grains are often larger than wind pollinated flowers and sticky

Which vector?Insect-pollinated flowers

Flowers pollinated by nocturnal insects often have a strong scent to attract; this scent is strongest at night. Eg Grevilia Leucopteris (smelly socks)

Some flowers mimic the shape of the female of the insect species to attract

Which vector?

• Bird-pollinated flowers– Often red or orange or yellow – these colours

recognised by birds as suitable sources for food– Generally not scented – vision not smell

important– Often petals form a tubular shape– Usually have nectaries inside the flower at the

base

Which vector?When birds access the nectaries they

dislodge the pollen from the stamen inside the floral tube and it coats the back of their head

Dispersing plant offspring• In flowering plants and conifers spread of the

next generation of plants occurs through a seed (embryo resulting from fertilisation of egg by pollen)

–In flowering plants the seeds are enclosed by fruit–In conifers the seeds are naked.

Seeds or fruits may move or be moved by;Sailing in the windDrifting on water currents (water proof coat)Hitchhiking on animals (hooks or spines to

attach)Hitchhiking in animals (bright coloured

berries, etc. Eaten – resistant to digestive enzymes)