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

Water relations and horticulture

HORT 301: Plant Physiology

Mike Mickelbart

Lecture outline

• Who cares about water?

• Review water movement in plants

• Examples of water relations in horticulture

Drought

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

Drought• Local

Drought• Global

Scarce water and population boom leads California to 'perfect drought'

Jun 25 2007 · 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 3 2007 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 23 2007 · Drought and advancing desert blamed for tensions

· Chad and southern Africa also at risk from warming

Source: Guardian Unlimited

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

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

– Driving force = water potential

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

– Driving force = water potential

w

w

w

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

– Driving force = water potential

w = p + s + g

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

– Driving force = water potential– Series of resistances

• Leaf• Xylem• Root• Soil

Transplant shock

• Soil water potential gradient

w = p + s + g + ?

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

• Turgor potential drives growth(1/V)(dV/dt) = (P-Y)

V = volume

= cell wall extensibility

P = turgor pressure

Y = yield threshold

©Ed Hume Enterprises

w = p + s + g + m

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

– Driving force = water potential

w = p + s + g

w = p + s + g + m

w

w

Poinsettia bract edge burn

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

– Driving force = water potential– Series of resistances

• Leaf• Xylem• Root• Soil

• Boundary layer

Greenhouse management• Leaf-air gradient

• Water uptake• Plant cooling• Nutrient uptake

• Air flow• Boundary layer

ABA and water loss

Partial root zone drying

Partial root zone drying

Partial root zone drying

Partial root zone drying

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

Yield (t/ha)

Water (Ml/ha)

Yield/water

15.2

1.4

10.9

15.4

0.7

22.0

Riesling Yield (t/ha)

Water (Ml/ha)

Yield/water

29.1

4.5

6.4

28.9

2.4

11.9

Riesling Yield (t/ha)

Water (Ml/ha)

Yield/water

30.6

5.2

5.9

28.7

2.6

10.9

Yield and water use of winegrapes

McCarthy, 2000

Partial root zone drying

Mass merchandising (box stores)• Handle large quantities of ornamentals

– Home Depot Garden Centers• 1990 $3.8 billion• 1994 $12.5 billion• 2006 >$25 billion

Mass merchandising (box stores)• Handle large quantities of ornamentals

– Home Depot Garden Centers• 1990 $3.8 billion• 1994 $12.5 billion• 2006 >$25 billion

ABA and water loss• ABA causes stomata to close

– Driving force = water potential– Series of resistances

• Leaf• Xylem• Root• Soil

Indiana Field Trial for ConTegoSupertunia ‘Citrus’

Control ConTego™ 1000 ppm

Photograph taken 10 days after withholding water

R. Lopez, Purdue Univ.

Indiana Field Trial for ConTegoColeus ‘Versa Crimson Gold’

Control ConTego™ 1000 ppm

Photograph taken 10 days after withholding water

R. Lopez, Purdue Univ.

Indiana Field Trial for ConTegoGerbera ‘Revolution’

Control ConTego™ 1000 ppm

Photograph taken 8 days after withholding water

R. Lopez, Purdue Univ.

Indiana Field Trial for ConTegoImpatiens hawkeri

Control ConTego™ 1000 ppm

Photograph taken 10 days after withholding water

R. Lopez, Purdue Univ.

Indiana Field Trial for ConTegoColeus ‘Versa Crimson Gold’

Treated Control

Plants were irrigated after the drought stress and planted in the Purdue Trial Gardens for evaluation. Photo is 44 d after treatment.

R. Lopez, Purdue Univ.

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