Integration and Control

1. Integration and Control • Animals? • Plants?

2. Integration and Control • Animals? • nervous impulses & hormones • Plants? • phytohormones

3. Important Plant Functions • Growth - • increase in size • increase organs - roots, stems, leaves • orient favorably in the environment • seedling growth • growth of adult organs (?)

4. Phototropism • First investigated by Charles and Frances Darwin (1881) • canary grass Phalaris canariensis L. • The Power of Movement in Plants (1881) • Seedlings • coleoptile • plumules

5. Phototropism

6. Phototropism - Darwins’ Experiment • Conclusion: • Some chemical is produced in the tip and transmitted down the stem to somehow produce bending. • There is a growth-promoting messenger.

7. Phototropism - Fritz Went’s Experiment • Dutch Plant Physiologist 1929 • Oat seedlings • Diffusion of phytohormone from growing tip in agar blocks • Agar blocks placed on oat seedlings

8. Phototropism - Fritz Went’s Experiment

9. Phototropism - Fritz Went’s Experiment • Conclusion: • A growth substance (phytohormone) must be (1) produced in the tip; (2) transmitted down the stem; and somehow (3) accumulate on the side away from the light. • “Auxin” (to increase, by Went) • Either • H.1: is destroyed on the lighted side • or • H.2: migrates to the dark side

10. Phototropism

11. Distribution of Auxin in an Oat Seedling(Avena savita) • Auxins are produced in growing tips (meristems); transmitted in the phloem. Basipetal, Acropetal

12. Distribution of Auxin in an Oat Seedling(Avena savita) • Polar Transport *Auxins are produced in growing tips (meristems); transmitted in the phloem. Basipetal, Acropetal Influx carriers basal efflux carriers Becomes protonate in CW space

13. Distribution of Auxin in an Oat Seedling(Avena savita) • Polar Transport *Auxins are produced in growing tips (meristems); transmitted in the phloem. Basipetal, Acropetal Influx carriers protonate IAA basal efflux carriers nonprotonate IAA- Becomes protonate in CW space

14. Naturally Occurring Auxins have been chemically isolated and analyzed(acid side chain on a aromatic ring) • Fig15-2a

15. Synthetic Auxins (precursors) • Fig15-2b

16. Synthetic Auxins (precursors) • 2, 4-D and 2,4,5-T are herbicides for broad-leaved plants at very low concentrations. • Widely used commercially for 30 years - defoliant in Viet Nam. • Contaminant of 2,4,5-T • tetrachlorobenzo-para-dioxin “dioxin”

17. Other Normal Effects of Auxins in Plants • 1. Phototropism • ------ • 2. Cell Elongation • causes polysaccharide cross-bridges to break and reform

18. Other Normal Effects of Auxins in Plants • 1. Phototropism • ------ • 2. Cell Elongation extensins

19. Other Normal Effects of Auxins in Plants 2. Cell Elongation extensins Phytohormones serve as signals - signal receptionion - transduction - response

20. Other Normal Effects of Auxins in Plants • 1. Phototropism • ------ • 2. Cell Elongation • 3. Geotropism

21. Other Normal Effects of Auxins in Plants • 1. Phototropism • ------ • 2. Cell Elongation • 3. Geotropism (Gravitropism) • 4. Initiation of adventitious root growth in cuttings • 5. Promotes stem elongation and inhibits root elongation

22. Other Normal Effects of Auxins in Plants • 6. Apical Dominance

23. Other Normal Effects of Auxins in Plants • 6. Apical Dominance • 7. Leaf Abscission - Abscission Layer - pectin & • cellulose • ethylene -> • pectinase & • cellulase

24. Other Normal Effects of Auxins in Plants • 7. Leaf Abscission

25. Other Normal Effects of Auxins in Plants • 1. Phototropism • 2. Cell Elongation • 3. Geotropism (Gravitropism) • 4. Initiation of adventitious root growth in cuttings • 5. Promotes stem elongation and inhibits root elongation • 6. Apical Dominance • 7. Leaf Abscission • 8. Maintains chlorophyll in the leaf • 9. Seedling Growth • 10. Fruit Growth (after fertilization) • 11. Parthenocarpic development

26. Other Normal Effects of Auxins in Plants • 11. Parthenocarpic development • (Pollination -> fertilization -> ovary development) • Massart 1902 • dead pollen grains -> fruit development in orchids • Fitting 1910 • pollen extract -> fruit development in orchids • Yasuda 1934 • pollen extract -> fruit development in cucumbers • pollen extract -> auxins (IAA) • Gustafson 1936 • IAA paste -> fruit development in several plants

27. Auxins • Work at very small concentrations (500 ppm) • Action Spectrum: primarily blue • Tryptophan is the primary precursor • Auxins must be inactivated at some point by forming conjugates or by enzymatic break down by enzymes such as IAA oxidase

28. Trypophan-dependent Biosynthesis of IAA

29. Bound Auxins(To inactivate - IAA-conjugates)

30. Bound Auxins(To inactivate - IAA-conjugates)

31. Bound Auxins(To inactivate - Decarboxylation)

32. Gibberellins • Isolated from a fungal disease of rice - • “Foolish Seedling Disease” • Gibberella fugikuroa • Isolated in the 1930’s Japan • Gibberellic Acid (GA)

33. Gibberellins • Gibberellic Acid • 125 forms of Gibberellins

34. Gibberellins • Produced mainly in apical meristems (leaves and embryos). Are considered terpenes (from isoprene).

35. Gibberellins

36. Gibberellins • Produced mainly in apical meristems (leaves and embryos).

37. Gibberellins • At least 125 different forms. • Produced mainly in apical meristems. • Low concentration required for normal stem elongation.

38. Gibberellins • Low concentration required for normal stem elongation.

39. Gibberellins • Low concentration required for normal stem elongation. • Can produce parthenocarpic fruits (apples, pears …)

40. Gibberellins • Low concentration required for normal stem elongation. • Can produce parthenocarpic fruits (apples, pears …) • Important in seedling development. • breaking dormancy • early germination

41. Gibberellins • Low concentration required for normal stem elongation. • Can produce parthenocarpic fruits (apples, pears …) • Important in seedling development.

42. Gibberellins

43. Gibberellins • Important in seedling development. • Controls the mobilization of food reserves in grasses.

44. Gibberellins • Important in seedling development. • Controls the mobilization of food reserves in grasses. • - cereal grains

45. Gibberellins • Important in seedling development. • Controls the mobilization of food reserves in grasses.

46. Gibberellins • Important in seedling development. • Controls the mobilization of food reserves in grasses.

47. Gibberellins • Controls bolting in rosette-type plants. • Lettuce, cabbage (photoperiod) • Queen Ann’s lace, Mullein (cold treatment) • premature bolting

48. Gibberellins • Controls bolting in rosette-type plants. • Important factor in bud break.

49. Gibberellins • Controls bolting in rosette-type plants. • Important factor in bud break. • Promotes cell elongation and cell division.

50. Gibberellins • Controls bolting in rosette-type plants. • Important factor in bud break. • Promotes cell elongation and cell division. • Antisenescent.