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Phytochrome Action

Phytochrome Action. Plant Physiology 2009 UNI. The pigment phytochrome. Detects R and FR light Provides information about environment Answers 3 questions for plant Am I in the light? Do I have plants as neighbors or above me? Is it time to flower?. Seed location?.

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Phytochrome Action

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  1. Phytochrome Action Plant Physiology 2009 UNI

  2. The pigment phytochrome • Detects R and FR light • Provides information about environment • Answers 3 questions for plant • Am I in the light? • Do I have plants as neighbors or above me? • Is it time to flower?

  3. Seed location? Red light from sun penetrates to seed. No light from sun to this deep seed. Seed germinates. No germination. Red light to seed = near surface

  4. Why bother? • Seeds store materials to start growth • Must reach light before running out of stored materials • Small seeds • Need to be very near surface • Often need light for germination • Germinating plants straighten & open leaves at surface, too

  5. Plant neighbors? Red absorbed by other plants. Far red reflected from other plants. Far red enriched = neighbors

  6. Why does this matter? • Neighboring plants are threats • Might grow taller, shade you • Solution • Grow at least as tall as neighbors • Need to know that you have neighbors • Isolated plants typically shorter than crowded plants • Other reasons, too

  7. Under other plants? Far red reflected from other plants or transmitted. Red absorbed by other plants. Far red enriched = understory

  8. Why important? • Best growth strategy for understory plants is different than for plants in open • Need to know whether • Shaded by other plants OR • Just cloudy OR • Late in day (low light)

  9. Right time to flower? • Unreliable indicators of time of year • Temperature • Moisture • Light levels • Reliable: length of day/night • Varies with season • Varies with latitude • Detected by phytochrome

  10. Phytochrome has 2 forms • Red-absorbing phytochrome • Far red absorbing phytochrome • Interconverted • Two forms of the same compound • Total amount same Pr Pfr Pr Pfr

  11. In red light Pfr Pr Pfr Pr absorbs red light, changes to Pfr form. Pfr doesn’t absorb red light, stays the same.

  12. In far red light Pr Pfr Pr Pr doesn’t absorb far red light, stays the same. Pfr absorbs far red light, changes to Pr form.

  13. Sunlight Mostly red A little far red

  14. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr In sunlight In sunlight most P gets converted to Pfr form.

  15. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Start of night Most P in Pfr form.

  16. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr In the dark Pfr form changes gradually to Pr form.

  17. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr After a short night Pfr still left.

  18. LDP = SNP • Needs short night • Needs Pfr still present at end of night • Pfr promotes flowering for LDPs

  19. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Later in the night More Pfr changes to Pr.

  20. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr After a long night All the Pfr is gone.

  21. Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Pfr Day dawns Most P gets converted to Pfr form again.

  22. SDP = LNP • Needs long night • Needs Pfr gone at end of night • Pfr inhibits flowering for SDPs

  23. LDP SDP Long day: Pfr left at end of short night. Pfr promotes flowering for LDPs. Pfr inhibits flowering for SDPs. Short day: Pfr gone at end of long night. No Pfr to promote flowering for LDPs. No Pfr to inhibit flowering for SDPs.

  24. Waiting for the right time • Plants grow leaves until it is time to flower • LDPs wait until the day is long enough • Really night short enough • Some time before June 21 • SPDs wait until the day is short enough • Really night long enough • Some time after June 21 • Flower opening happens later

  25. Day neutral plants • Flower when mature enough • Maybe other environmental signals (temp?) • Day length (dark length) doesn’t matter

  26. Through the year May Specific flowers at specific times. September July August October June

  27. Phytochrome tells plants • If they are near the surface • About their plant neighbors • Whether it is time to flower • And lots more

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