Horticulture test 3
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Created by:
kathrynbergin on March 28, 2012
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65 terms
Terms | Definitions |
|---|---|
 leaf area | smaller leaf area decreases transpiration |
| leaf orientation | vertically oriented leaves decrease transpiration |
| leaf surface | waxy, hairy or shiny leaf surfaces decrease transpiration |
| stomata | when stomata are closed, transpiration decreases |
| ENVIRONMENTAL FACTOR: humidity | high humidity decreases transpiration |
| ENVIRONMENTAL FACTOR: temperature | a) low temp. decreases transpiration b) high temp. increases transpiration, but when it gets too hot the stomata close, then transpiration may decrease |
| ENVIRONMENTAL FACTOR: light intensity | 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. |
| ENVIRONMENTAL FACTOR: wind | as wind increases transpiration increases, but if it gets too windy, stomata may close and transpiration may decrease. |
| ENVIRONMENTAL FACTOR: soil water | 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. |
| DECREASE TRANSPIRATION: antitraspirants | chemicals that close or clog stomata TWO TYPES: a) physiologically cause stomatal closure b) wax, resin or latex that clogs stomata |
| Soil | 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 |
| absorption | uptake of water by roots |
| translocation | movement of water through plants, mainly through xylem |
| guttation | -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 |
| Air | approx. 25% of volume; in larger pores |
| Water | approx. 5% of volume; in smaller pores |
| Mineral Particles | 44-49% of volume |
| Organic Matter | typically about 1% in nature |
| litter | partially decayed organic matter on the soil surface |
| humus | 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 |
| Silt | 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 |
| pH | 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) | P |
| 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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