Learn to Think Like a Plant: Talk to Them!

1. Learn to Think Like a PlantThen You Can Talk to ThemDavid Wm. ReedDepartment of Horticultural SciencesTexas A&M University

2. Plants are “schizophrenic hermits” !They “live alone” and “talk to themselves” Plants “talk” using: • Hormones • Moving photosynthates, nutrients, etc. from “sources” to “sinks” • Sensing their environment (day vs. night, day length, length of winter, temperature, rainfall, structures they touch, gases in the air, chemicals in the soil, etc.) • They possess the senses of sight, touch, smell and taste • To the best of my knowledge, they cannot hear?

3. Learn Plant Language • We must learn the “language” plants use. • Plants don’t use “words” or “nerve impulses”. • Rather they use hormonal signals, chemical signals, and environmental signals that “trigger metabolism” and “turn genes on and off”. • If we learn their “communication logic”, then we can “talk” to them and “dictate “ what they do.

4. We’re Going to Talk About • How plants “see” • Their “favorite temperature” • How they know when they are “cut” • How and why they sometimes “kill’ themselves or parts of themselves • A little about their “sexual preference”

5. Let’s “talk” to plants withLight

6. How do plants “see”? Plants “see” with: • Chlorophyll • absorbs light for photosynthesis • Carotenoids • also absorbs light for photosynthesis • protects plants from high light and sunburn • Phytochrome • determines when the sun rises and sets • assists in determining day length (photoperiod)(actually plants measure night length!)

7. Why are leaves green?

8. Chlorophyll & CarotenoidAbsorption Spectrum(these are the colors of light that power photosynthesis) Plants primarily use red and blue light for photosynthesis Plants are “partially color blind” to green light.

9. Emission Spectrum ofArtificial Lights Each light has a unique color spectrum

10. Which light is the best match for photosynthesis?

11. Let’s “talk” to plants withTemperature

12. Photosynthesis – RespirationInteraction From: http://ecosys.cfl.scf.rncan.gc.ca/dynamic/photosyn_e.htm

13. Photosynthesis – RespirationInteraction At optimum temperatures: photosynthesis greatly exceeds respiration “net food storage” As temperature increases: • respiration increases (especially night time) • photosynthesis deceases (some enzymes inactivated) At high temperatures: respiration approaches or exceeds photosynthesis “net food depletion” and the plant starts starving

14. Cool Season Crops in the South Optimum Temperature = 65 to 75 oF • Grow great during fall, winter and spring • Because their photosynthesis greatly exceeds respiration In the heat of late spring and early summer Respiration approaches or exceeds their photosynthesis The plants may begin starving to death.

15. Cool Season Plants in the South Over-seeded ryegrass Daffodil • Cool season plants die in summer because: • non-adapted species may not store sufficient food to come back the next year (ex. tulip) • adapted species will store sufficient food in underground storage organ and only the top dies (ex. ephemerals, daffodil) • set seed and “kill” themselves (winter annual, ex. rye)

16. Warm Season Crops in Texas Optimum Temperature = 80 to 90 oF • Grow great during early and late summer • Because their photosynthesis exceeds respiration Texas Summers Upper 90s oF most of July & August • In mid-summer, their photosynthesis & respiration are more equal • Therefore, even some warm season plants don’t grow very much in the heat of the summer in Texas • Many warm season plants only have a flush of spring growth; and may not flush again in late summer/early fall • Many plants actually go into quiescence in mid-summer in Texas

17. High Night Temperatures • High night temperatures that are most critical. • High night respiration rates “burns-up” photosynthates produced during the day. Cool-season crops starve to death Warm-season crops go into a summer quiescence By the way, it is what also ruins our fall color!

18. Winter Dormancy or Rest A strategy for temperate perennial plants to survive winter. Trigger? short days & decreasing temperatures. Cause? > inhibitors (ABA) & < promoters (auxin, GA) Overcome? 2-8 weeks constant cold storage @ 32 to 45 oF 200-1,200 cumulative hours outdoors @ 32 to 45 oF

19. How do you “tell” a plant to come out of winter dormancy or rest? Stratification Required for most temperate plant seeds. Match Chilling Requirement & Chilling Zone Required for most spring flowering temperature perennial fruit trees, ornamental trees & shrubs

20. Match Chilling Requirement with Chilling Zone

21. Let’s “talk” to plants aboutDeathand Decapitation

22. Plant Suicide Plants often kill themselves or part of themselves. On a routine basis! And, on purpose! • Summer & winter annuals • Leaf abscission (drop) • Flower petals • Fruit Usually, the signal is the “death hormone” ethylene

23. Horticulturist Murder Plants Horticulturist often kill plants by causing inadvertent exposure to the “death hormone” ethylene • Cut flowers and fruit stored enclosed • One rotten apple can spoil the whole barrel or the whole bouquet • Not “emasculating” flowers • Improperly adjusted heaters

24. Ethylene is Dr. Jekyll and Mr. Hyde Ethylene is not always the bad guy “Mr. Hyde” Ethylene as “Dr. Jekyll” • stimulates bromeliads to flower • stimulates the formation of pistillate (female) flowers on monoecious plants • stimulates adventitious roots on some plants • can be used as a defoliant for transplanting Ethylene can also be the good guy “Dr. Jekyll”

25. Plant Decapitation What happens when you decapitate a stem? • Auxin is produced by the young leaves around the shoot tip. • Auxin is responsible for apical dominance. • Decapitation alters the flow of auxin down the stem.

26. What happens when you decapitate a stem? Adventitious Root Formation Auxin accumulates at the cutwhich stimulates adventitiousroot formation Lateral Buds Break Dormancy Apical dominance is removed because the flow of auxin downthe stem is stopped.

27. How do you “tell” a plant tolook ugly?

28. Dehorning or Pollarding You can be convicted of “crape murder” for doing this!

29. Let’s “tell” a plant how to growinto an attractive, pleasing and functional shape.

30. Pruning to Direct Growththinning-out vs. heading-back

31. Let’s let the plant “tell us”exactly where to make the “surgical cuts”

32. Target Pruning • A technique developed by Dr. Alex Shigo • When a limb is cut, plants will seal-off the inside of the xylem (e.g. wood). • This is called “compartmentalization” • Target pruning is a “surgical cut” along the line of compartmentalization • Anatomically, the “surgical cut” is made along a straight line just outside the “bark ridge” to the top of the “branch collar”

33. Target Pruning From: www.clemson.edu/crapemyrtle/pruninginstructions.htm If you cannot see the branch collar,roughly it is from just outside thebark ridge at a downward and slightly outward angle. From: www.rittenhouse.ca/hortmag/images/oak.jpg

34. Target Pruning Target pruning according to Alex Shigo

35. Prune Weak Crotches Selectively remove weakcrotches, i.e. narrow crotch angleswith bark inclusions

36. Prune Weak Crotches Selectively remove weakcrotches, i.e. narrow crotch angles This must be done when the tree is young; even ifit disfigures the tree!!!! Remember, trees arepruned for the next generation!

37. Let’s “talk” to plants about theirSexual Preference

38. Sexual Preference in Plants Monoecious Plantspossess both staminate (male) and pistillate (female) flowers on the same plant cucurbits pecan begonia oak corn papaya* * Actually papaya are sexually confused, they can “go every which way”

39. “Why are all my cucumber flowers falling off?” No ovary, i.e. “babycucumber” at baseof flower.These are staminate (male) flowers. “Well mame, it’s because those “useless” male flowers that emerge early in the spring don’t make babies!!!!!”

40. Pistillate (female) cucumber flowers Ovary, i.e. “babycucumber” “Don’t worry mame, your cucumber plants will startmaking female flowers a bit later in the spring.” “Let me tell you how you can “talk” yourcucumbers into making more female flowers.”

41. Sexual Preference in Plants The sex of some monoecious plants can be manipulated with hormones Ethylene Favors pistillate (female) flower formation Gibberellic Acid Favors staminate (male) flower formation

42. Finally My wish for today is thatI said at least one thing that “rocked your world”