Lesson 2 - Flowers - Lecture Notes

Flowers
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Flower Organs

• Sepals protect the flower bud and can look like small leaves or petals.

• Petals are usually colorful and attract pollinators/give them a place to land.

• Stamens are the male reproductive structure, the female reproductive structure
is called the pistil.

Flowers
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Flower Adaptations

Structural differences

• Flowers that have sepals, petals, stamens, and one or more pistils are called
complete flowers.

• If a flower is missing one or more of these organs, it is an incomplete flower.

• Flowers that have both stamens and pistils are perfect flowers

• Flowers that only have functional pistils or stamens are called imperfect flowers.

Flowers
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Flower Adaptations

Structural differences

• The number of flower organs distinguishes monocots from eudicots.

• Monocots generally have organs in multiples of three.

• Eudicots usually have organs in multiples of 4 or 5.

• All organs tend to occur in the same multiple of three, four, or five.

Flowers
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Flower Adaptations

Pollination mechanisms

• Flower adaptations that relate to pollination include flower size, shape, color,
and petal arrangements.

• Self pollination: flowers can pollinate themselves or other flowers on the same
plant.

Flowers
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Flower Adaptations

Pollination mechanisms

• Cross pollination: flowers rely on pollinators for reproduction.

• Animal pollination: flowers are brightly colored or strongly scented to attract
pollinators

• Wind pollination: flowers lack showy or fragrant flowers, produce large
amounts of lightweight pollen.

Flowers
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Flower Adaptations

Photoperiodism

• Some plants only flower in response to a specific number of hours of
uninterrupted darkness.

• This flowering response is known as photoperiodism.

• Flowering plants are divided into four different groups based on the critical
period, which is based on the amount of daylight.

Flowers
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Flower Adaptations

Short-day photoperiodism

• A short-day plant (long-night plant) flowers when exposed daily to a number of
hours of darkness that is greater than its critical period.

Flowers
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Flower Adaptations

Long-day photoperiodism

• A long-day plant (short-night plant) flowers when the number of hours of
darkness is less than its critical period.

Flowers
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Flower Adaptations

Intermediate-day photoperiodism

• An intermediate-day plant flowers as long as the numbers of hours of darkness is
neither too great or too few.

Flowers
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Flower Adaptations

Day-neutral photoperiodism

•A day-neutral plant flowers over a range in the number of hours of darkness.