Transcript Flowers and Reproduction

FLOWERS AND REPRODUCTION
Dr. Gough
FIGURE 09.07A: (A) THE SEPALS OF THIS ROSE FORM A TIGHT COVERING OVER THE REST
OF THE FLOWER AS IT DEVELOPS, PROTECTING THE INNER PARTS.
FLOWER STRUCTURE

Ovary Position

Protect ovary from pollinators
Fig. 9-28
FLOWER STRUCTURE
Stem with leaf-like structures
 Terminology
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Pedicel and receptacle
Complete vs. incomplete flowers
Sepals (calyx)
Petals (corolla)
Stamens (androecium)
Carpels (gynoecium)
REPRODUCTION

Two forms of reproduction
Produce identical genetic copies
 Produce genetically different offspring

What conditions favor which form?
 How does sexual reproduction produce
genetically different offspring?
 Some plants reproduce both ways
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ASEXUAL REPRODUCTION
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Many methods
Fragmentation
 Rhizomes
 Stolons
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FIGURE 09.02C: (C) ALL THE TREES IN THIS PHOTOGRAPH ARE A PART OF THE SAME
PLANT, EACH A SPROUT FROM A SINGLE ROOT SYSTEM.
SEXUAL REPRODUCTION
In angiosperms, requires flowers
 Plant Life Cycle
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Think of human/animal life cycle
Meiosis
 Fertilization
 Mitosis
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More complicated in plants
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“alternation of generations”
FIGURE 09.13: THIS IS THE TIP OF A GROWING POLLEN TUBE. IT WAS TREATED TO MAKE
THE NUCLEI FLUORESCE SO THAT THEY CAN BE FOUND DESPITE BEING SO SMALL.
Courtesy of S. Muccifora
SEXUAL REPRODUCTION
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Fertilization
Following pollination
 Pollen tube growths through style to ovule opening
 One sperm nucleus fertilizes egg
 Second sperm nucleus migrates into central cell
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Only in angiosperms
 Becomes endosperm
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“Double fertilization”
SEXUAL REPRODUCTION
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Embryo and Seed Development
Zygote continues dividing, growing
 Embryo
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Radicle
 Hypocotyl
 Epicotyl
 Monocotyledon
 Dicotyledon

FIGURE 09.19A: (A) THIS BEAN SEED HAS BEGUN GERMINATING; THE RADICLE HAS
EXTENDED AND WILL DEVELOP INTO A TAPROOT.
FIGURE 09.19C: (C) THE SMALL LEAVES PRESENT ON THE EPICOTYL ARE EXPANDING
DURING GERMINATION.
SEXUAL REPRODUCTION
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Fruit Development
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Fruit is a mature ovary
FIGURE 09.21: IN APPLES, THE PETALS DIE AND FALL OFF AFTER POLLINATION.
FIGURE 09.22B: (B) COCONUTS IN STORES ARE USUALLY JUST THE ENDOCARP AND SEED.
FLOWER STRUCTURE AND CROSSPOLLINATION
Role of flowers in pollen and seed dispersal
 Cross-pollination
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Vs. self-pollination
Stamen and style maturation times
 Stigma and pollen incompatibility
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FLOWER STRUCTURE AND CROSSPOLLINATION

Monoecious and dioecious species
Imperfect vs. perfect flowers
 Monoecy
 Dioecy
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Fig. 9-25
FLOWER STRUCTURE AND CROSSPOLLINATION
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Animal-pollinated flowers
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Coevolution between plants and pollinators
Plant-insect pollination began about 120 mya
 What traits were favored?
 Some birds and bats pollinate too
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Flower shape
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Actinomorphic/regular vs. zygomorphic
Usually positive relationship, but cheaters on both
sides
FRUIT TYPES AND SEED DISPERSAL
More co-evolution!
 Seed (fruit) dispersal agents
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Gravity
 Wind
 Water
 Animals
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Often division of labor within fruit