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.

Dispersing plant offspring Seeds or fruits may move or be moved by; Sailing in the wind Drifting 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)