BIOLOGY 220 LECUTRE #25 - 11-29-07

BIOLOGY 220 LECUTRE #25 - 11-29-07 - BIOLOGY 220 LECTURE#25...

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BIOLOGY 220 – LECTURE #25 - Flowers, Pollination, and Seed Dispersal PLANT REPRODUCTION – 3 Angiosperms Pollen grain lands on stigma – we get the growth of the pollen tube from that pollen grain – grows down into the tube and into the ovary and embryo sac Sperm cells are released – fuse with zygote and polar nuclei to make an endosperm or a zygote PLANT REPRODUCTION – 4 Angiosperms Organs to do reproduction – found in flower – STRUCTURES ARE IMPORTANT!!!!!! Hermaphrodite flower – 90% of all plant species have hermaphroditic flowers – they have both male and female organs. The flower structures is arranged in what we call “ whirls ” – radial sets of organs 1.) The first whirl is the outermost whirl – it consist of the connective tissues that connects the flower to a little stem called receptacle – also consists of fleshy leafy parts called sepals Main function of sepals is to protect the developing flower – when the flower is in its bud the sepals protect it – more tough than petals 2.) The next whirl is called the corolla – Consists of just the petals 3.) The third whirl – called the androecium – fancy name for where the male parts are at – has stamens, which are long filaments with an anther sitting on top – anther is the structure where pollen is produced. 4.) At the center of flowers there are one or more carpels , and that’s referred to the gynoecium – female o Carpel is divided into four big parts : 1.) Stigma – fleshy pad where pollen lands 2.) Styol – connective tube that runs down towards the ovary The Stimga + Styol – together are called the pistol 3.) Ovary 4.) Ovule You end up with these four chunks – listed on slide – All of these structures are determined by only three types of genes
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PLANT REPRODUCTION – 5 Angiosperms It’s the combination of different types of genes that tells us what kind of floral organs are expressed in which whirl In a normal one – the outermost tissues on the floral meristem only expressed genes of class A – when only those are expressed you get sepals. Express class A and class B genes – you get petals Express class B and class C genes – you get stamens PLANT REPRODUCTION – 6 Angiosperms You want to get pollen to fertilize ovules – get the gametes together Plants can self-pollinate o This only works in hermaphrodites – but most plants are! Also, wind pollination !
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BIOLOGY 220 LECUTRE #25 - 11-29-07 - BIOLOGY 220 LECTURE#25...

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