1. Water relations and horticulture
HORT 301: Plant Physiology
Mike Mickelbart

2. Lecture outline Who cares about water? Review water movement in plants
Examples of water relations in horticulture 2

3. Drought 3

4. Franklin, Tennessee, Aug 27, 2007. <0
Franklin, Tennessee, Aug 27, <0.1” rain in Aug, >14 days with temperatures at or above 100°F, Water restrictions currently in effect. Photo courtesy of Jordan Gerth. 4

6. Drought
Local 6

7. Drought
Global
Scarce water and population boom leads California to 'perfect drought'
Jun · No rain forecast in south of state until September · Sprinklers and car washing could be stopped
Turkey rations water as cities hit by drought
Aug Turkey's two major cities are grappling with water shortages after record low levels of snow and rain in the winter and searing summer temperatures.
Darfur conflict heralds era of wars triggered by climate change, UN report warns
Jun · Drought and advancing desert blamed for tensions
· Chad and southern Africa also at risk from warming
Source: Guardian Unlimited 7

8. The main question
How does water move into and out of plants? 8

9. The main question How does water move into and out of plants?
Driving force = water potential 9

10. The main question How does water move into and out of plants?
Driving force = water potential w w w 10

11. The main question How does water move into and out of plants?
Driving force = water potential
w = p + s + g
\figures\ch04\pp04161.jpg

12. The main question How does water move into and out of plants?
Driving force = water potential
Series of resistances
Leaf
Xylem
Root
Soil 12

13. Transplant shock w = p + s + g + ? Soil water potential gradient13

14.  = cell wall extensibility
Fruit growth
Turgor essential for fruit growth
fruit create water stress in trees
excessive turgor leads to splitting
Splitting in fruits
Changes in turgor
Cell wall elasticity
©Ed Hume Enterprises
Turgor potential drives growth
(1/V)(dV/dt) = (P-Y)
V = volume
 = cell wall extensibility
P = turgor pressure
Y = yield threshold
w = p + s + g + m

15. The main question How does water move into and out of plants?
Driving force = water potential
w = p + s + g
\figures\ch04\pp04161.jpg

16. w = p + s + g + m w w 16

17. 17

18. Poinsettia bract edge burn18

19. The main question How does water move into and out of plants?
Driving force = water potential
Series of resistances
Leaf
Xylem
Root
Soil 19

20. Boundary layer 20

21. Greenhouse management
Leaf-air gradient
Water uptake
Plant cooling
Nutrient uptake
Air flow
Boundary layer 21

22. ABA and water loss 22

23. Partial root zone drying23

24. Partial root zone drying24

25. Partial root zone drying25

26. Partial root zone drying
Yield and water use of winegrapes
Variety
Variable
Control
PRD
Shiraz
Yield (t/ha)
Water (Ml/ha)
Yield/water
22.6
1.4
16.1
21.5
0.7
30.7
Cabernet sauvignon
15.2
10.9
15.4
22.0
Riesling
29.1
4.5
6.4
28.9
2.4
11.9
30.6
5.2
5.9
28.7
2.6
McCarthy, 2000 26

27. Partial root zone drying27

28. Mass merchandising (box stores)
Handle large quantities of ornamentals
Home Depot Garden Centers
1990 $3.8 billion
1994 $12.5 billion
2006 >$25 billion

29. Mass merchandising (box stores)
Handle large quantities of ornamentals
Home Depot Garden Centers
1990 $3.8 billion
1994 $12.5 billion
2006 >$25 billion

30. ABA and water loss ABA causes stomata to close
Driving force = water potential
Series of resistances
Leaf
Xylem
Root
Soil 30

31. Indiana Field Trial for ConTego Supertunia ‘Citrus’
Control
ConTego™ 1000 ppm
Photograph taken 10 days after withholding water
R. Lopez, Purdue Univ.

32. Indiana Field Trial for ConTego Coleus ‘Versa Crimson Gold’
Control
ConTego™ 1000 ppm
Photograph taken 10 days after withholding water
R. Lopez, Purdue Univ.

33. Indiana Field Trial for ConTego Gerbera ‘Revolution’
Control
ConTego™ 1000 ppm
Photograph taken 8 days after withholding water
R. Lopez, Purdue Univ.

34. Indiana Field Trial for ConTego Impatiens hawkeri
Control
ConTego™ 1000 ppm
Photograph taken 10 days after withholding water
R. Lopez, Purdue Univ.

35. Indiana Field Trial for ConTego Coleus ‘Versa Crimson Gold’
Plants were irrigated after the drought stress and planted in the Purdue Trial Gardens for evaluation. Photo is 44 d after treatment.
Treated
Control
R. Lopez, Purdue Univ.

36. Water relations and horticulture
Water movement
Water potential gradients
Resistances to water movement
Gradients in horticulture
Soil gradients
Organ gradients (fruit/stem/leaves)
Leaf to air gradients (RH)
Resistances in horticulture
Stomatal resistance
ABA 36