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ANGIOSPERMS The flowering plants © 2008 Paul Billiet ODWS Spring crocus Crocus vernus Flower structure Flowers are reproductive structures The have evolved to send and receive pollen from one flower to another This is process of pollination Flowers are developed from a series of modified leaves These leaves are arranged in a rings (whorls) © 2008 Paul Billiet ODWS Types of pollination Wind Animal Water Bumble bee Bombus hortorum on red clover Trifolium pratense Yorkshire fog grass Holcus lanatus © 2008 Paul Billiet ODWS Animal pollination Usually insects Also other flying animals e.g. hummingbirds or fruit bats Cerambycid beetle pollinating bramble Rubus fruticosus © 2008 Paul Billiet ODWS Flower structure Dog rose Rosa canina © 2008 Paul Billiet ODWS Flower structure Stigma Style Ovary Petal Anther Sepal Filament © 2008 Paul Billiet ODWS Pollination Pollen grains contain the male gametes of the plant They are picked up by a pollinator and transferred to another flower Plants tend to specialise in pollinators This ensures the pollen is delivered to same species of plant Yellow archangel Lamiastrum galobdolon being pollinated by a bumble bee Bombus hortorum © 2008 Paul Billiet ODWS Pollination Small skipper Thymelicus flavus on marsh thistle Cirsium palustris © 2008 Paul Billiet ODWS Pollination The honey bee Apis melifera on marsh thistle Cirsium palustris © 2008 Paul Billiet ODWS Pollination Some flowers are highly specialised to encourage only one type of insect Fox glove flowers Digitalis purpurea © 2008 Paul Billiet ODWS Pollination Most species of flowering plants are hermaphroditic Pollen from a flower could land on the stigma of the same flower or another flower on the same plant = self pollination Pollen transferred from the anther on one flower to the stigma of another flower on a different plant = cross pollination © 2008 Paul Billiet ODWS Fertilisation Pollination ≠ Fertilisation The male gamete (the male nucleus) has to get to the egg cell The egg cell lies in an ovule in an ovary at the centre of the plant The pollen grain germinates on the stigma It grows a pollen tube down the style It male nuclei travel down the pollen tube to the ovule © 2008 Paul Billiet ODWS Fertilisation Pollen grain Stigma Style Ovule Embryo sac Ovary © 2008 Paul Billiet ODWS Pollen tube Fertilisation Embryo sac Polar nuclei Egg cell Micropyle © 2008 Paul Billiet ODWS Fertilisation Pollen grains of the daisy Bellis perennis © 2008 Paul Billiet ODWS Fertilisation Germinating pollen grains of blue bell, Hyacinthoides non-scripta © 2008 Paul Billiet ODWS The double fertilisation Ovule Nucellus Pollen tube Male nucleus + 2 polar nuclei = endosperm nucleus (3n) Male nucleus + egg cell = zygote (2n) © 2008 Paul Billiet ODWS Pollen tube entering micropyle From flower to fruit Marsh marigold Caltha palustris © 2008 Paul Billiet ODWS Fruits and seed dispersal Animal dispersal Strawberry Fragaria vesca Explosive dispersal Bird’s foot trefoil Lotus corniculatus Animal dispersal Wood avens Geum urbanum Wind dispersal Ragwort Senecio © 2008 Paul Billiet ODWS
