The Atmospheric EnvironmentThe Atmospheric Environment

Atmospheric EnvironmentAtmospheric Environment

MacroenvironmentMacroenvironment - up to 5 ft above the - up to 5 ft above the ground, representative of the overall climateground, representative of the overall climate

MicroenvironmentMicroenvironment - immediate vicinity of - immediate vicinity of the turfgrass plant, ranging from the canopy the turfgrass plant, ranging from the canopy surface to the bottom of the rootzonesurface to the bottom of the rootzone

ClimateClimate

LightLight TemperatureTemperature MoistureMoisture WindWind Relative HumidityRelative Humidity

Light AbsorptionLight Absorption

Vital to lifeVital to life Affected by mowing, leaf areaAffected by mowing, leaf area Affected by leaf angleAffected by leaf angle Influenced by surroundingsInfluenced by surroundings

cloudsclouds buildingsbuildings treestrees Clippings - light exclusion!Clippings - light exclusion!

The Fate of Solar RadiationThe Fate of Solar Radiation

ReradiationReflection Absorption (heat)

Transmission

Absorption (chemical)

Light QualityLight Quality

Visible Spectrum

InfraredUltra-violet

400 nm 700 nm

Light QualityLight Quality

Visible Spectrum

InfraredUltra-violet

Photosynthesishas two peaks inthe visible range

Light Duration Affects Form of Cool Season Grasses

Light Duration Affects Form of Cool Season Grasses

Short days (spring and fall) affect:Short days (spring and fall) affect: increased densityincreased density greater tillering/stolons/rhizomesgreater tillering/stolons/rhizomes shorter leavesshorter leaves more leavesmore leaves smaller shootssmaller shoots more prostrate growth habitmore prostrate growth habit

Opposite occurs in long days of summerOpposite occurs in long days of summer

Light IntensityLight Intensity

Seasonal Seasonal LatitudeLatitude Time of dayTime of day Atmospheric screeningAtmospheric screening TopographyTopography

Sufficient Light Intensity is required to sustain adequate

photosynthesis and thus growth.

All turfgrasses prefer to grow in full sunlight.

Sufficient Light Intensity is required to sustain adequate

photosynthesis and thus growth.

All turfgrasses prefer to grow in full sunlight.

Three Components of Photosynthesis:Three Components of Photosynthesis: Compensation point - where the light level Compensation point - where the light level

is low and just adequate to produce enough is low and just adequate to produce enough photosynthesis to match respiration. The photosynthesis to match respiration. The net gain of carbon is net gain of carbon is zerozero..

Intermediate light levels produce enough Intermediate light levels produce enough carbohydrates to compensate for nighttime carbohydrates to compensate for nighttime respiration, plus enough extra to support respiration, plus enough extra to support new growth and sustain tissuenew growth and sustain tissue

Three Components of Photosynthesis:Three Components of Photosynthesis: High light, where photosynthesis is high High light, where photosynthesis is high

enough to produce extra carbohydrate that enough to produce extra carbohydrate that can be stored. Excessively high light may can be stored. Excessively high light may be damagingbe damaging

Temperature and other stresses can affect the Temperature and other stresses can affect the ability of a turf to effectively utilize higher ability of a turf to effectively utilize higher light levels light levels

Photosynthetic Light CurvePhotosynthetic Light CurveP

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Light Level

0

Low Medium Full Sun

Carbohydrate Storage

Maintenance

Compensation Point

Inhibition

Physiological Responses to Low LightPhysiological Responses to Low Light Higher chlorophyll contentHigher chlorophyll content Lower respirationLower respiration Lower compensation pointLower compensation point Reduced carbohydrate reservesReduced carbohydrate reserves Lower demand for water, nutrientsLower demand for water, nutrients Reduced heat, cold, drought, wear toleranceReduced heat, cold, drought, wear tolerance

Photosynthetic Light CurvePhotosynthetic Light CurveP

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Light Level

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Low Medium Full Sun

Shade-adapted Sun-adapted

Developmental Responses to Low LightDevelopmental Responses to Low Light Reduced growthReduced growth Thinner leavesThinner leaves Reduced shoot density; Reduced tilleringReduced shoot density; Reduced tillering Longer, more erect leavesLonger, more erect leaves Leaves are more succulent (less substance)Leaves are more succulent (less substance) Longer internodesLonger internodes Slower establishmentSlower establishment

Shade Increases DiseaseShade Increases Disease

Thinner leaves less resistantThinner leaves less resistant Sun inhibits spore germinationSun inhibits spore germination Higher humidity increases spore Higher humidity increases spore

germinationgermination

Shade is not just Reduced LightShade is not just Reduced Light Light quality can change as it passes through Light quality can change as it passes through

the tree canopy. The tree leaves “remove” the tree canopy. The tree leaves “remove” the red and blue light components, leaving the red and blue light components, leaving mainly the green, which is not effective in mainly the green, which is not effective in photosynthesisphotosynthesis

Shade moderates air temperaturesShade moderates air temperatures Shade is associated with increased humidity, Shade is associated with increased humidity,

which may increase heat load, diseaseswhich may increase heat load, diseases

Shade from Trees:Shade from Trees:

Tree roots compete for water and nutrients. Tree roots compete for water and nutrients. Where are the tree roots?Where are the tree roots?

Deciduous trees present extra problem in Deciduous trees present extra problem in fall when leaves are shed. This can lead to fall when leaves are shed. This can lead to extreme light exclusion. How to handle?extreme light exclusion. How to handle?

AllelopathyAllelopathy - some tree roots exude specific - some tree roots exude specific chemicals which interfere with turf growthchemicals which interfere with turf growth

Best Species for Shade ToleranceBest Species for Shade Tolerance

Cool SeasonCool Season Tall fescueTall fescue Fine fescuesFine fescues BentgrassBentgrass

Warm SeasonWarm Season St. AugustineSt. Augustine ZoysiaZoysia CentipedeCentipede

Managing for ShadeManaging for Shade Thin tree canopy. Also increases wind, reduces Thin tree canopy. Also increases wind, reduces

humidityhumidity Raise cutting heightRaise cutting height Reduce N fertilityReduce N fertility Irrigate deeply, infrequentlyIrrigate deeply, infrequently Control trafficControl traffic Fungicides to control diseaseFungicides to control disease Fertilize tree roots separatelyFertilize tree roots separately

TemperatureTemperature

The most important environmental factor The most important environmental factor affecting the adaptation of turfgrasses to a affecting the adaptation of turfgrasses to a particular geographic region. particular geographic region.

Growth generally confined to > 40Growth generally confined to > 40oo, < 105, < 105o o FF Temperatures fluctuate depending on the Temperatures fluctuate depending on the

amount of energy received from the sunamount of energy received from the sun

Heat can be Transferred from One Environmental Component

to Another

Heat can be Transferred from One Environmental Component

to Another EvaporationEvaporation ReradiationReradiation ConductionConduction ConvectionConvection AdvectionAdvection

Turf Modifies TemperaturesTurf Modifies Temperatures Temperature extremes much less with turf Temperature extremes much less with turf

surface than with bare soil, pavingsurface than with bare soil, paving Turf absorbs a substantial amount of energyTurf absorbs a substantial amount of energy Much of the energy is dissipated by one of the Much of the energy is dissipated by one of the

transfer processes. The most important is transfer processes. The most important is evapotranspirationevapotranspiration (ET, total loss of water (ET, total loss of water from turf and soil surface). from turf and soil surface).

Turf Modifies TemperaturesTurf Modifies Temperatures Evaporation requires large input of energy, Evaporation requires large input of energy,

which is “used up” by converting water from which is “used up” by converting water from liquid to gas. This is called the liquid to gas. This is called the latent heat of latent heat of evaporationevaporation

Where does the heat come from to evaporate Where does the heat come from to evaporate the water? From the turfgrass plant and the water? From the turfgrass plant and surroundings.surroundings.

Turf Response to TemperatureTurf Response to Temperature

MinimumMinimum MaximumMaximum OptimumOptimum

60-75 60-75 oo for cool season shoot growth for cool season shoot growth 80-95 80-95 o o for warm season shoot growthfor warm season shoot growth

Root growth can continue as long as soil Root growth can continue as long as soil temperatures are favorabletemperatures are favorable 50-65 50-65 o o for cool seasonfor cool season 75-85 75-85 oo for warm season for warm season

Temperature Effects on RootsTemperature Effects on Roots

Optimum temperatures produce white, long, Optimum temperatures produce white, long, multi-branched rootsmulti-branched roots

Sub-optimal temperatures produce white, Sub-optimal temperatures produce white, shorter, slower growing, less branched rootsshorter, slower growing, less branched roots

Supra-optimal temperatures produce roots Supra-optimal temperatures produce roots that become brown, spindly, mature rapidly, that become brown, spindly, mature rapidly, die faster, and aren’t replaced as fast.die faster, and aren’t replaced as fast.

High Temperature Stress(often associated with drought stress)High Temperature Stress

(often associated with drought stress) Indirect:Indirect:

rapid turnover of roots, resulting in loss of root systemrapid turnover of roots, resulting in loss of root system decrease in shoot growth, perhaps due to reduction in decrease in shoot growth, perhaps due to reduction in

photosynthesis, carbohydrates. May lead to summer photosynthesis, carbohydrates. May lead to summer dormancydormancy

Direct:Direct: High temps can kill turf. High temps can kill turf. Crown, young leaf, apical meristem are more tolerant Crown, young leaf, apical meristem are more tolerant

than older tissuethan older tissue

Heat Hardiness of CS TurfgrassesHeat Hardiness of CS Turfgrasses

Tall Fescue, Creeping BentTall Fescue, Creeping Bent

Kentucky BluegrassKentucky Bluegrass

Fine FescuesFine Fescues

Perennial RyegrassPerennial Ryegrass

Annual RyegrassAnnual Ryegrass

Highest

Lowest

Low Temperature StressLow Temperature Stress

Direct stress: when the liquid inside the cell Direct stress: when the liquid inside the cell freezes. Cells may rupture, proteins denature. freezes. Cells may rupture, proteins denature. Depends on level of tissue hydration Depends on level of tissue hydration Prevent by correcting compacted soilsPrevent by correcting compacted soils Avoid excessive fall nitrogenAvoid excessive fall nitrogen Maintain adequate potassium, phosphorusMaintain adequate potassium, phosphorus Minimize thatch accumulationMinimize thatch accumulation

Aerial ComponentsAerial Components COCO2 2 and Oand O22 are important in the plant and in the are important in the plant and in the

soil. Low levels of COsoil. Low levels of CO22 in the plant will limit in the plant will limit

photosynthesis. Low levels of Ophotosynthesis. Low levels of O22 in the soil limit in the soil limit

root respiration and thus root function. When root respiration and thus root function. When does soil Odoes soil O22 become a problem? become a problem? When soils are warm and microbial respiration is highWhen soils are warm and microbial respiration is high During flooding or pondingDuring flooding or ponding When surface is sealed, diffusion is lowWhen surface is sealed, diffusion is low

WindWind

Evaporative coolingEvaporative cooling Increases ET, evapotranspirationIncreases ET, evapotranspiration Deposits soil, sand, snow, seeds, pollen, Deposits soil, sand, snow, seeds, pollen,

spores spores Wind-blown sand as abrasiveWind-blown sand as abrasive Enhances COEnhances CO2 2 exchange. How?exchange. How?

The Atmosphere: approx. 360 CO2 molecules per 1 million total gas molecules

The Atmosphere: approx. 360 CO2 molecules per 1 million total gas molecules

Stomates on a Leaf SurfaceStomates on a Leaf Surface

Stomate Opening

StomatalCavity

Epidermal cells

Wind keeps CO2 replenished

Stomate Opening

StomatalCavity

Epidermal cells

“Dead” Air Becomes Depleted of CO2

Sources/Forms of WaterSources/Forms of Water

PrecipitationPrecipitation IrrigationIrrigation Dew and guttationDew and guttation Gaseous - Relative HumidityGaseous - Relative Humidity

Dew and GuttationDew and Guttation

Dew is condensation caused by differences Dew is condensation caused by differences in temperature between air and a surface. in temperature between air and a surface. How does this happen in turf?How does this happen in turf?

Guttation occurs when the plant absorbs Guttation occurs when the plant absorbs more water from the soil than it loses more water from the soil than it loses through the stomates. The excess is exuded through the stomates. The excess is exuded through cut leaf ends or through special through cut leaf ends or through special pores called hydathodes, at the leaf tipspores called hydathodes, at the leaf tips

GuttationGuttation

Occurs at night, shortly after fertilizing with Occurs at night, shortly after fertilizing with soluble N fertilizers and with frequent soluble N fertilizers and with frequent irrigationirrigation

Liquid contains sugars, salts, amino acids, a Liquid contains sugars, salts, amino acids, a perfect growth medium for pathogensperfect growth medium for pathogens

Guttation is removed to reduce disease and Guttation is removed to reduce disease and to improve mowing quality, reduce to improve mowing quality, reduce clippings from clumpingclippings from clumping

Relative HumidityRelative Humidity

Can influence night temperature. High Can influence night temperature. High humidity reduces long wave reradiation, humidity reduces long wave reradiation, which keeps surfaces warmer. Desert turf which keeps surfaces warmer. Desert turf cools off at night due to low humidity, cools off at night due to low humidity, permits CS turf to be grown in very hot permits CS turf to be grown in very hot climates. climates.

Controls the amount of dewControls the amount of dew Partly controls evaporative coolingPartly controls evaporative cooling