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How do plants know when to flower?

How do plants know when to flower?. The Phytochrome System. Flowering of plants is determined in part by the length of the day. long days & short nights. short days & long nights. Plants are of three general types: Example. strawberry. short-day. spinach. long-day.

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How do plants know when to flower?

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  1. How do plants know when to flower? The Phytochrome System

  2. Flowering of plants is determined in part by the length of the day. long days & short nights short days & long nights

  3. Plants are of three general types: Example strawberry short-day spinach long-day day-neutral sunflower

  4. Short-day plants flower in spring or autumn when the day lengths are shorter than the critical day length.. For example, the common cocklebur (Xanthium strumarium) is induced to flower only when exposed to 16 hours or less of light.

  5. Examples of short-day plants : poinsettias strawberries primroses.

  6. Long day plants flower chiefly in the summer and will flower only when exposed to light for longer than a critical length. Spinach has a critical daylength of 13 hours.

  7. Examples of long-day plants spinach lettuce henbane

  8. What determines if plants are long or short-day is not so much the length of the exposure time but whether it is longer or shorter than some critical interval.

  9. Day-neutral plants flower without respect to daylength. Examples of day-neutral plants corn sunflower cucumber

  10. cucumber

  11. Plants contain a photoreceptor called phytochrome (P) which comes in two forms which are interconvertible, Pr and Pfr. Pr Pfr

  12. Pr absorbs red light andPfr absorbs far-red light.

  13. Visible light lies between 400 and 700 nm.

  14. Red light Far Red light 730nm 660 nm

  15. The Electromagnetic spectrum

  16. Light induced synthesis Pr Dark reversion Red light Far-red light Physiological response Slowly reverts during the night. Straight away Pfr Straight away

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