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AngiospermsCh 19

Angiosperms

• Cycadophyta• Ginkgophyta• Coniferophyta Gymnosperms

• Gnetophyta • Anthophyta

Anthophyta

• 300,000 and possibly up to 450,000 spp.• Largest phylum of photosynthetic

organisms.R i i f 100 t ll & 20 i• Range in size from 100m tall & 20m in girth to 1 millimeter long.

Duckweed - Lemnaceae

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Flowering plant of L. gibbaMonocots

• Cocos nucifera

• Musa x paradisiaca

• Oryza sativa

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Dicots

• Carnegiea gigantea • Anemone americana

• Eschscholizacalifornica

Parasites & Saprophytes

• Cuscuta salina– Dodder– Parasite

Morning glory family– Morning glory family

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• Rafflesia arnoldii– Parasite on Vitaceae– World’s largest flower

• Monotropa uniflora– Saprophyte

Flowers• Determinate shoot

– Bears sporophylls• Carpels contain ovules

– Develops into seeds– Carpel itself develops into the fruit wall

• Flowers clustered into aggregations– Inflorescences

• Stalk of an inflorescence or of solitary flower called peduncle• Stalk of an individual flower in an inflorescence called pedicel• Part of the flower stalk to which the flower parts are attached is

termed the receptacle

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• Flowers include 2 sets of sterile appendages– Sepals & Petals

Attached below fertile parts– Attached below fertile parts• Stamens & Carpels

– Fertile parts

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http://www.missouriplants.com/Whitealt/Geum_canadense_sepals.jpg

Collectively called: Calyx

Collectively called: Corolla

http://www.highhopesgardens.com/Blogphotos/2007/flower1.jpg

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Calyx + Corolla

http://www.flowershopnetwork.com/blog/wp-content/imagescaler/a69c112b8c60f8867caccb5d99a78342.jpg

Stamens

• Collectively called – androecium– “House of Man”– Microsporophylls

St i t f l d t lk• Stamen consists of slender stalk– Filament

• Two-lobed anther – Four microsporangia or pollen sacs

http://t1.gstatic.com/images?q=tbn:ANd9GcQ6VNcqTGH85eR4MKC5xESC-qS7aGZimKkYH5m-NvFe9lxb3XBRng

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Carpels

• Ovule-bearing parts– “Gynoecium”– Megasporophylls folded lengthwise

• Enclose one or more ovules• Enclose one or more ovules

• Individual carpel or fused carpel– “Pistil”

• Carpels differentiated into 3 parts– Lower part

• Ovary – encloses the ovules– Middle part– Middle part

• Style – through which pollen tubes grow– Upper part

• Stigma – receives the pollen

http://www.botany.hawaii.edu/faculty/webb/bot311/bot311-00/angiosperm/ClintoniaCarpelLab_small.jpg

Ovules attached to ovary

• Portion of ovary where ovules originate and to which they remain attached is called:

Placenta– Placenta– Arrangement known as placentation

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Types of placentation

Parietal – ovules borne on ovary wall

Axile – ovules borne on central column of tissue

Free central – ovules borne on central column; not connected

Variations in Flower Structure

• Perfect flowers– Both stamens & carpels

• Imperfect flowersIf ith t l i i– If either stamens or carpels are missing

• Depending on part present flower is either:– Staminate– Carpellate (pistillate)

• If both staminate & pistillate flowers occur on same plant– Monoecious “single house”

If staminate and pistillate flowers occur on• If staminate and pistillate flowers occur on separate plants– Dioecious “two house”

Staminate Flowers Derived from pistillate flowers

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Position of ovary

• Superior– If sepals, petals, and stamens attach to

receptacle below ovary

• Inferior – Sepals, petals, and stamen attach near top of

the ovary

http://www.google.com/imgres?q=inferior+ovary&hl=en&client=firefox-a&hs=sD3&sa=X&rls=org.mozilla:en-US:official&biw=1680&bih=944&tbm=isch&prmd=imvns&tbnid=Qcnh7o2p-nDW_M:&imgrefurl=http://www.biologie.uni-hamburg.de/b-online/vascular/ros.htm&docid=f6ma9UqnIBWO7M&imgurl=http://www.biologie.uni-hamburg.de/b-online/vascular/images/cha_sp.jpg&w=600&h=400&ei=39-yTtnlIeuGsAKj-4D4Aw&zoom=1

• Hypogynous– Situated on receptacle beneath the ovary

• EpigynousA i f t f– Arise from top of ovary

• Perigynous– Stamens & petals adnate to calyx– Form hypanthium

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Epigyny Perigyny

Microsporogenesis & Microgametogenesis

• Nutritive cells – tapetum

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• Microsporogenesis– Completes with formation of the single –

celled microspores, or pollen grains.

• Microgametophyte– Mature male

gametophyte

Megasporogenesis & Megagametogenesis

• Culminates in formation of an egg & polar nuclei

Two young ovules:Each with a single, large megasporophyte surrounded by nucellus

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Ovule now developed integuments with a micropyle.

Ovule with 8-nucleate embryo sac.

Only 6 seen here.

Double fertilization & Pollination unique in Angiosperms

• Two sperm cells and tube remain together until discharged into the embryo sacembryo sac

• Involvement of both sperm in this process unlike Gymnosperms: – Union of one with egg & one with polar nuclei– “Double Fertilization”– Shared only with Ephedra & Gnetum

• Triple fusion– Fusion of one sperm nuclei to two polar nuclei– Results in triploid (3n) primary endosperm

nucleus.

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• After double fertilization, several processes occur leading to the seed & fruit– Primary endosperm nucleus divides

• Forming endosperm• Forming endosperm– Zygote develops into an embryo.– Integuments develop into a seed coat.– Ovary wall & related structures develop into a

fruit.

Summary

• Angiosperms constitute the Phylum Anthophyta

• The flower is a determinate shoot bearing sporophyllssporophylls

• Pollination followed by fertilization• Ovule develops into a seed• Ovary develops into a fruit