Upload
tristin-maury
View
226
Download
3
Tags:
Embed Size (px)
Citation preview
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)