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leaf area

smaller leaf area decreases transpiration

leaf orientation

vertically oriented leaves decrease transpiration

leaf surface

waxy, hairy or shiny leaf surfaces decrease transpiration


when stomata are closed, transpiration decreases


high humidity decreases transpiration


a) low temp. decreases transpiration
b) high temp. increases transpiration, but when it gets too hot the stomata close, then transpiration may decrease


a)darkness decreases, b/c stomata close (except for CAM plants open at night)
b) high light intensity increases temp. which increases transpiration, until stomata close then transpiration may decrease; occurs midday during heat of summer.


as wind increases transpiration increases, but if it gets too windy, stomata may close and transpiration may decrease.


a) when soil is moist, transpiration occurs according to the above factors
b) when soil is too dry, stomata close causing transpiration to decrease (overrides above factors)

DECREASE TRANSPIRATION: mist or spray foilage

a) in propagation an intermittent mist system is used
b) mid-afternoon sprinkler irrigate plants in greenhouses/nurseries

DECREASE TRANSPIRATION: decrease light intensity

grow plants under shade

DECREASE TRANSPIRATION: harden off seedlings

a) decrease watering
b) decrease temperature
c) decrease fertilizer, especially N.


chemicals that close or clog stomata
a) physiologically cause stomatal closure
b) wax, resin or latex that clogs stomata


the outer weathered layer of the earth's crust

growing medium

the substrate in which plants grow. Usually appied to manufactured or synthetic soils.. EX: "potting soild", or highly amended soils (landscape beds)

Functions of soil or growing medium

1. Support and anchorage
2. Supplies mineral nutrients
3. Supplies water
4. Allows gas exchange- especially O2 and CO2, but also ethylene

Soil profile

morphology of horizons (layers) in a soil

A Horizon or topsoil

-highly weathered
-abundant life, therefore, high in organic matter
-dark coloed

plow plan

a compacted, impermeable layer in the A horizon due to repeated plowing or tilling (approx. 6 inches deep)

B Horizon or subsoil

-less weathered; higher in clay
- less life, therefore, low in organic matter
-lighter colored

clay pan

impermeable layer high in clay

hard pan

impermeable layer high in iron

C Horizon or parent material

-little weathered
-little life, except deep rooted plants and little to no organic matter

D Horizon or bedrock

- rock base


uptake of water by roots


movement of water through plants, mainly through xylem


-loss of liquid water from leaves
- occurs through hydathodes (similar to stomata, but they do not close)

young roots

most absorption, manly through roots hairs

YOUNG ROOTS: very numerous

14 billion on a typical rye plant

YOUNG ROOTS: large surface area

14,000 ft2 (1310 m2) on a typical rye plant

YOUNG ROOTS: rapidly and constantly produced

975 linear ft (300 m) er day on a squash plant

older roots

little absorption due to:
a) suberization of endodermis
b) periderm (bark) formation

Cohesion Theory of Translocation in the Xylem

1) Transpiration occurs and is driving force
2) Causes negative pressure in leaves
3) Column of water is pulled up in the xylem and translocated

driving force for translocation

transpiration causes a negative pressure in leaves, which "pulls" the water up the xylem

evaporative coling of leaves

540 cal of heat energy is dissipated for every gram of water that evaporates from leaves, which is a major contributor to the cooling of leaves

Organic Soil

contain 20% or more organic matter

peat soil

contains greater than 65% organic matter (Sphagnum is the BEST)

muck soil

contains 20-65% organic matter

Mineral Soil (field soil)

contains less than 20% organic matter

4 Major Components (in a well watered, but well drained loam soild)

air, water, mineral particles, organic matter


approx. 25% of volume; in larger pores


approx. 5% of volume; in smaller pores

Mineral Particles

44-49% of volume

Organic Matter

typically about 1% in nature


partially decayed organic matter on the soil surface


highly decomposed, fine, amorphous organic matter in the soil

SAND: Physical

structurally simple; relatively unweathered, physically broken down parent material

SAND: Chemical

relatively inert; results in:
a) a little effect on soil chemistry and pH
b) poor nutrient holding capacity (CEC)

Pore Space

a) less total pore space
b) more large (macro) pores, fewer small (capillary) pores

Sand causes...

1) increased aeration
2) increased drainage
3) decreased water capacity


intermediate chemical and physical properties between clay and sand

CLAY: Physical

structually complex
a) colloidal
b)wet: viscous and gelantinous; sticky--dry: hard, packed and cohesive
c) Micelles: laminated into stacks
d) very large surface area
e) very small pores

CLAY: Chemical

very complex; negatively charged.... more


negative log of the hydrogen ion concentration

Low pH (below pH 5.5)

Cu,Zn, had B,Fe with a Mn

Intermediate pH (pH 6-7)


High pH 9above pH 6.5)

Mo, N, K Ca,S,Mg

Chemicals that increase pH

lime, dolomite, nitrate

Chemicals that decrease pH

sulfur, sulfate, acidic fertilizers (urea, ammonia, ammonium)

Acid soils

soils with acid pH; in areas of high rainfall

Basic or Alkaline soils

soils with basic pH; in arid regions

BASIC: saline soil

pH 7-7.5 and greater than 2,000 ppm total soluble salts

BASIC: sodic soil

pH 8.5-10, 15% or more of CEC is occupied by Na.

BASIC: saline-sodic soil

pH 8-8.5, greater than 2,000 ppm total soluble salts and 15% or more of CEC occupied by Na

3 ways to improve saline, sodic, or saline-sodic soils

leach-- application of large volumes of water to remove excess soluble salts
Add element sulfur (S)-- acidifies the soil
Add gypsum-- Ca promotes good soil structure, drainage and Na leaching

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