ANGIOSPERMS The flowering plants Spring crocus Crocus vernus
Jan 21, 2016
ANGIOSPERMSThe flowering plants
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)
Types of pollination Wind Animal Water
Bumble bee Bombus hortorum on red clover Trifolium pratense
Yorkshire fog grass Holcus lanatus
Animal pollination Usually insects Also other flying
animals e.g. hummingbirds or
fruit bats
Cerambycid beetle pollinating bramble Rubus fruticosus
Flower structure
Dog rose Rosa canina
Flower structureStigma
Style
OvaryPetal
Sepal
Filament
Anther
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
Pollination
Small skipper Thymelicus flavus on marsh thistle Cirsium palustris
Pollination
The honey bee Apis melifera on marsh thistle Cirsium palustris
Pollination Some flowers are
highly specialised to encourage only one type of insect
Fox glove flowers Digitalis purpurea
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
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
Fertilisation
Style
StigmaPollen grain
Ovule
Embryo sac
Pollen tubeOvary
Fertilisation
Egg cell
Polar nuclei
Embryo sac
Micropyle
Fertilisation
Pollen grains of the daisy Bellis perennis
Fertilisation
Germinating pollen grains of blue bell, Hyacinthoides non-scripta
The double fertilisation
Pollen tube
Pollen tube entering micropyle
Male nucleus + egg cell
= zygote (2n)
Male nucleus + 2 polar nuclei = endosperm nucleus (3n)
OvuleNucellus
From flower to fruit
Marsh marigold Caltha palustris
Fruits and seed dispersalAnimal dispersal Strawberry Fragaria vesca
Wind dispersal Ragwort Senecio
Explosive dispersal Bird’s foot trefoil Lotus corniculatus
Animal dispersalWood avens Geum urbanum