Title: Chap 10. Temperature
1Chap 10. Temperature
- Temperature and Heat Units
- Thermal Properties of Water
- Movement of Heat Energy
- Biological Influence of Temperature
- Dew Point and Frost
- Thermal Belt and Temperature Inversion
- Temperature Control for Crop Protection
- Controlled Environment Agriculture (CEA)
2Heat of Vaporization
- Heat is absorbed from surrounding when water
evaporates - Heat of vaporization 970 BTU per lb of water
evaporated - Greenhouse cooling by the pad-and-fan
evaporative system
3Pad-and-fan evaporative cooling system
- Evaporative pad on one side wall and fans
mounted on the other side wall - Flow of cooled air from pad area to fan area
(one air exchange/min) - Maximum distance from pad to fan 200 feet
- Temperature differential (?T) between pad and
fan areas is usually 7 oF - Greenhouse air can be cooled down to the
wet-bulb temperature
Cool-cell pad
Exhaust fans mounted on the side wall
4Psychrometric Chart
- Illustrates the thermal properties of air
- Dry-bulb temperature
- Air temperature of sensible heat
- measured by dry-bulb thermometer
- Wet-bulb temperature
- Temperature of an aspirated thermometer
- measured with the bulb encased in a
water - saturated wick
Measure the room temperature Dry-bulb temp
________oF Wet-bulb temp ________oF
5Greenhouse Cooling with High-Pressure Fogging
System
- Use high-pressure (1000 psi) to generate fog
(size 25-40 µ diam) - Use stainless steel pipe to prevent corrosion
problem - Use low-salinity de-ionized water to prevent
clogging of nozzles - More efficient in cooling the ambient air where
it is needed - Less disease and algae problem, compared to
misting system - Cost of installation high
Summer cooling of greenhouse with fogging system
High-pressure fogging
6Heat of Fusion
- Heat is released to surrounding when water
freezes - Heat of fusion is used to protect citrus fruits
from freezing
7Heat of fusion from ice formation protects citrus
crops exposed to freezing temperature in Florida
8Overhead water sprinkling on citrus crops in
Florida to save them from freezing
9Transfer of Heat Energy
10Temperature Influence in Biological System
11Cell Damage by Low Temperature
- Ice crystals rupture cell walls
- Intracellular or intercellular event
- Leakage of cell contents
- Readily occurs in tender plants
- Influence of extensin on cell wall
Ice crystals
Cell wall ruptures
Extensin (rupture-resistant)
12Cryogenic Storage
- Liquid nitrogen (-196 oC, -320 oF)
- Permanent storage of pollen, seed, meristems
13Thermal Belt
- Good site for locating an orchard
- Usually on a sloped hill side
- North-facing slope is better the south-facing
slope
cold
warm
warm
cold
warm slope
warm slope
Normal Condition
Temperature Inversion
14Peach orchard located on a thermal belt, Western
Slope, Colorado
15Fruit growing area in Oregon
16Grape orchards (vinyards) in Napa Valley,
California
Frost damage in vinyards is not as severe in
other orchards because flowering of grapes occurs
after shoot emergence
17Prevention of frost damage by movement
Windmills and helicopters are used to mix the air
to prevent frost damage on fruit crops during
temperature inversion
18Use of Plastic Mulch
19Strawberry Production in California
20Frost Damage on Strawberry Plants in California
A
B
Normal
Damaged
B. Crop failure often results from freezing of
flower parts that are delicate and fragile.
Stigmas and anthers are easily damaged by light
freeze and become incapable of pollination and
fertilization.
A. Freezing of leaves is often initiated by the
presence of ice nucleating active (INA) bacteria
that secrete proteins that act as primers for ice
crystal formation
21Ice Nucleating Active (INA) Bacteria on
Strawberries
- INA bacteria secrete protein on the leaf
- Protein serves as a primer for ice crystal
formation - Mutant INA bacteria secrete defective proteins
(ice-) - Mutant proteins are incapable of forming Ice
crystals
Wild type INA bacteria
Mutant type INA bacteria
defective protein
Ice crystals formed on the leaf ? frost damage
No ice crystals formed on the leaf ? no frost
damage
22Smudging in a fruit orchard to prevent frost
injury
23Plant Growing Structures
- Controlled Environment Agriculture (CEA)
- Cold Frames
- Hotbeds
- Cloches and Plastic Tunnels
- Greenhouses
- Shade and Lath Houses
24Cold Frame
25Cloches or Hotbeds
26Use of Hotcaps for Vegetable Production
27Standard Peak Greenhouses
28Gutter-connected Standard Peak Greenhouses
29Construction of a Modern Greenhouse
30Quonset House
31Air Inflated plastic greenhouses
32Air Inflated Greenhouse with no internal support
structure
33Geodesic Dome Greenhouse