unit 5: temperature & light chapters 8 & 9. unit 5: temperature & light unit 5...

Unit 5: Temperature & Unit 5: Temperature & LightLight

Chapters 8 & 9Chapters 8 & 9

Unit 5: Temperature & LightUnit 5: Temperature & Light

Unit 5 Objectives:Unit 5 Objectives: Identification of major cool/warm season Identification of major cool/warm season

cropscrops Understand how temperature effects plantsUnderstand how temperature effects plants Use of growing degree daysUse of growing degree days Discussion on the effect of light on plantsDiscussion on the effect of light on plants Understanding of day length and photoperiodUnderstanding of day length and photoperiod Awareness of light quality and intensityAwareness of light quality and intensity


Biological Temperature RangeBiological Temperature Range Plants vary in their ability to tolerate temp Plants vary in their ability to tolerate temp

differencesdifferences Each plant has a lower temp at which it cannot Each plant has a lower temp at which it cannot

grow, a zone in which growth is optimized, and a grow, a zone in which growth is optimized, and a upper temp limit in which growth will again stopupper temp limit in which growth will again stop

Common crops can be divided into Common crops can be divided into Cool-Cool-seasonseason and and Warm-seasonWarm-season categories categories Cool-season – survive mild spring frosts, may be Cool-season – survive mild spring frosts, may be

planted early spring or in fallplanted early spring or in fall


Examples:Examples: Lettuce, Onions, Turnips, CabbageLettuce, Onions, Turnips, Cabbage Can you name some others?Can you name some others?

Warm-season – usually killed by frosts, require Warm-season – usually killed by frosts, require warmer temps to grow properly, planted later in warmer temps to grow properly, planted later in springspring

Examples:Examples: Cotton, Peas, Peppers, TomatoesCotton, Peas, Peppers, Tomatoes Can you name the rest?Can you name the rest?

Some plants have adapted to various temp Some plants have adapted to various temp ranges in order to surviveranges in order to survive


Others cannot survive at allOthers cannot survive at all Tropical plants, annualsTropical plants, annuals

HardeningHardening Cool-season vegetables can be adapted to cooler Cool-season vegetables can be adapted to cooler

temps by gradually exposing young plants to temps by gradually exposing young plants to cooler tempscooler temps

Allow to wilt slightly before wateringAllow to wilt slightly before watering Grow at 10Grow at 10º below normalº below normal

Plants become tougher, less likely to die from low Plants become tougher, less likely to die from low levels of stresslevels of stress


Temperature and DormancyTemperature and Dormancy Ex. Trees dropping their leaves, or wheatEx. Trees dropping their leaves, or wheat Bulbs and some weeds can be killed off to the Bulbs and some weeds can be killed off to the

ground but survive on the underground parts of the ground but survive on the underground parts of the plantplant

Also seeds are able to overwinter (the worst weeds are Also seeds are able to overwinter (the worst weeds are good at this)good at this)

Most can only survive in dormancy to a certain Most can only survive in dormancy to a certain lower templower temp

Survivability may depend:Survivability may depend: Length of cold spell, wind, temp, age of plant, soil Length of cold spell, wind, temp, age of plant, soil

moisturemoisture


Spring warm spells followed by quick cold snap Spring warm spells followed by quick cold snap can be very deadlycan be very deadly

Not all parts of a plant can go dormantNot all parts of a plant can go dormant Ex. Flower buds on peach trees, cold kills flowers, but Ex. Flower buds on peach trees, cold kills flowers, but

tree survivestree survives

Seed GerminationSeed Germination Temperature determining factor is seed Temperature determining factor is seed

germinationgermination Temp must be in the optimal zone for germination Temp must be in the optimal zone for germination

to occurto occur Too cold or too hot will deter proper germinationToo cold or too hot will deter proper germination


ThermoperiodThermoperiod Daily temp rangeDaily temp range Maximum growth occurs when day temp is ~15Maximum growth occurs when day temp is ~15º º

higher than night temphigher than night temp Allows the plant to photosynthesize and respire at Allows the plant to photosynthesize and respire at

optimal rate during the day, and rest at nightoptimal rate during the day, and rest at night Growth only occurs when photosynthesis is greater Growth only occurs when photosynthesis is greater

than respirationthan respiration Otherwise the plant expends time breaking down extra Otherwise the plant expends time breaking down extra

energyenergy

Plants vary also is this mannerPlants vary also is this manner Some prefer warmer or cooler night tempsSome prefer warmer or cooler night temps


Plants can be classified hardy or nonhardy Plants can be classified hardy or nonhardy depending on ability to withstand cold tempsdepending on ability to withstand cold temps

When might injury happen to nonhardy plants?When might injury happen to nonhardy plants?

Plants must still get water in the winterPlants must still get water in the winter Why? What is occurring in the soil?Why? What is occurring in the soil?

Climatic ClassificationClimatic Classification Can divide the U.S. into hardiness zones for Can divide the U.S. into hardiness zones for

plant growth (by USDA)plant growth (by USDA) Determines the types of plants that will grow based Determines the types of plants that will grow based

on the avg annual minimum tempson the avg annual minimum temps


North America divided into 11 zonesNorth America divided into 11 zones 1 coldest, 11 warmest1 coldest, 11 warmest

Zones pretty much follow logic, but there are Zones pretty much follow logic, but there are some variationssome variations Where might we find some exceptions?Where might we find some exceptions?

Not only hardiness zone must be taken into Not only hardiness zone must be taken into account, many other factors are still in playaccount, many other factors are still in play Soil types, rainfall, daytime temp, day length, wind, Soil types, rainfall, daytime temp, day length, wind,

humidity, heathumidity, heat Ex. Phoenix and Portland are both in Zone 8 – can we Ex. Phoenix and Portland are both in Zone 8 – can we

grow the same plants?grow the same plants?


Growers can use Hardiness Zones as a Growers can use Hardiness Zones as a general guideline, but must have extensive general guideline, but must have extensive local knowledgelocal knowledge

Growing Degree DaysGrowing Degree Days Used to estimate the growth and development Used to estimate the growth and development

of plants and insects during the growing of plants and insects during the growing seasonseason

Concept: development will only occur if temp Concept: development will only occur if temp exceed a minimum threshold or base temp exceed a minimum threshold or base temp (Tbase)(Tbase) Base temps are determined for each organism & Base temps are determined for each organism &

they’re all differentthey’re all different


Calculating GDDCalculating GDD Take avg of high and low temp for the dayTake avg of high and low temp for the day If that temp is at or below Tbase, GDD=0If that temp is at or below Tbase, GDD=0 If avg temp>Tbase then take that avg – Tbase = If avg temp>Tbase then take that avg – Tbase =

GDDGDD Lets do some examples:Lets do some examples:

High 47High 47ºº, Low 32, Low 32ºº Tbase for Wheat is 40Tbase for Wheat is 40ºº What is the GDD?What is the GDD? High 75º, Low 55ºHigh 75º, Low 55º What is GDD?What is GDD?


Modified GDDModified GDD Similar to previous GDD, except upper temp never Similar to previous GDD, except upper temp never

goes above 86goes above 86º, and low never goes below 50ºº, and low never goes below 50º If temps are outside these parameters they are reset to If temps are outside these parameters they are reset to

that constantthat constant

Used to monitor the development of cornUsed to monitor the development of corn Assumption is development is limited above 86ºAssumption is development is limited above 86º

Use of GDDUse of GDD Growth and development of plants and cold-Growth and development of plants and cold-

blooded animals depends on heat in and around blooded animals depends on heat in and around themthem


Used to help monitor growth, and predict pest or Used to help monitor growth, and predict pest or disease riskdisease risk

After base temp is exceeded growth begins, but it After base temp is exceeded growth begins, but it slows/stops if temp falls below the baseslows/stops if temp falls below the base

State of development correlated to the State of development correlated to the accumulation of daily GDD’s through the growing accumulation of daily GDD’s through the growing seasonseason

This data is very accessible from agricultural This data is very accessible from agricultural weather stations and on the webweather stations and on the web

Accuracy of the information is increasing as more Accuracy of the information is increasing as more data becomes available and relationships are data becomes available and relationships are establishedestablished


A Crop Production ExampleA Crop Production Example Corn hybrid maturity ratings are related to temp Corn hybrid maturity ratings are related to temp

effectseffects Most widely used system in U.S. has two facetsMost widely used system in U.S. has two facets

A corn plant must accumulate a certain amount of heat in A corn plant must accumulate a certain amount of heat in order to complete its life cycleorder to complete its life cycle

The total amount of heat needed will be relatively The total amount of heat needed will be relatively constant for a given hybridconstant for a given hybrid

Use GDD’s to calculate these maturitiesUse GDD’s to calculate these maturities Tbase is 50Tbase is 50º - corn makes little to no growth below º - corn makes little to no growth below

this tempthis temp Max is 86º - growth rate declines to due excess Max is 86º - growth rate declines to due excess

respiration and moisture stressrespiration and moisture stress


Rate from planting to physiological maturityRate from planting to physiological maturity GDD’s can then be used as a decision-making toolGDD’s can then be used as a decision-making tool

Choose hybrid fitting the season based upon intended Choose hybrid fitting the season based upon intended planting date to maximize season lengthplanting date to maximize season length

Can make adjustments to seed selection if planting is Can make adjustments to seed selection if planting is delayed based upon the number of possible GDD’sdelayed based upon the number of possible GDD’s

May help schedule harvestingMay help schedule harvesting

Not all seed companies use the same system, so Not all seed companies use the same system, so ask if this is going to be a tool you useask if this is going to be a tool you use


VernalizationVernalization Promotion of flowering by forcing cold Promotion of flowering by forcing cold

treatment to plantstreatment to plants Exposing to warmer temps early and Exposing to warmer temps early and

reversing the process called devernalizationreversing the process called devernalization Ex. Tulip bulbsEx. Tulip bulbs

Forcing cell activity in the meristematic tissueForcing cell activity in the meristematic tissue


Temperature StressTemperature Stress Effects many essential growth processes, Effects many essential growth processes,

including biological reactionsincluding biological reactions Reaction rates increase w/ tempReaction rates increase w/ temp

Ex. PhotosynthesisEx. Photosynthesis

Absorption of minerals and water also Absorption of minerals and water also affected by tempaffected by temp


High & Low Temp InjuryHigh & Low Temp Injury Low temp usually results in frost injuryLow temp usually results in frost injury

What are our frost free dates in this area?What are our frost free dates in this area? Warm spells in the spring can stimulate early growth Warm spells in the spring can stimulate early growth

which can then be killed by cold which can then be killed by cold

High temp injuryHigh temp injury Often related to light and water effectsOften related to light and water effects May kill cell protoplasmMay kill cell protoplasm


Nature of LightNature of Light Form or radiant energyForm or radiant energy

Travels in wavesTravels in waves Distance between called Distance between called wavelengthwavelength

Human eye sensitive to wavelength 400-700 nmHuman eye sensitive to wavelength 400-700 nm Called Called white lightwhite light

Made up of red, orange, yellow, green, blue, violetMade up of red, orange, yellow, green, blue, violet Each color has different wavelengthEach color has different wavelength Which is longest/shortest?Which is longest/shortest?

When light is trapped it becomes another form of When light is trapped it becomes another form of energyenergy

Ex. – absorbed energy becomes heatEx. – absorbed energy becomes heat


Photosynthetic organisms contain chlorophyll Photosynthetic organisms contain chlorophyll which is responsible for trapping light and which is responsible for trapping light and converting it to chemical energyconverting it to chemical energy

Plants appear green because chlorophyll reflects Plants appear green because chlorophyll reflects the green colorthe green color

Wavelengths absorbed by chlorophyll then called Wavelengths absorbed by chlorophyll then called absorption spectrumabsorption spectrum

Violet, red, and some blue are readily absorbed and Violet, red, and some blue are readily absorbed and changed to chemical energychanged to chemical energy


SunlightSunlight Minimum duration of sunlight required for Minimum duration of sunlight required for

survivalsurvival Light Quality & IntensityLight Quality & Intensity

Most ag plants require >6 hrs or full sunlight/d to Most ag plants require >6 hrs or full sunlight/d to produce respectable yieldsproduce respectable yields

Increased shade or clouds decreases yield and Increased shade or clouds decreases yield and plant appearanceplant appearance

Some plants have sun/shade preferences for Some plants have sun/shade preferences for optimal growthoptimal growth


Ex. Most garden plants prefer full sun, however Ex. Most garden plants prefer full sun, however leafing vegetables tolerate more shadeleafing vegetables tolerate more shade

Plant’s ability to move leaves to be parallel with a Plant’s ability to move leaves to be parallel with a light sourcelight source

Movement called Movement called phototropismphototropism

Light & GerminationLight & Germination Shoot grows up away from gravity, root grows to Shoot grows up away from gravity, root grows to

gravitygravity Response to gravity called Response to gravity called geotropismgeotropism

Shoots begin to synthesize food as soon as they Shoots begin to synthesize food as soon as they are exposed to lightare exposed to light


Shoots will try to reach light until the food in the Shoots will try to reach light until the food in the seed is used upseed is used up

Shoot will be white with no leaves until emergenceShoot will be white with no leaves until emergence Death occurs if food is depleted before emergenceDeath occurs if food is depleted before emergence White stem w/ little leaf growth called White stem w/ little leaf growth called etoliatedetoliated

Light Absorption & PhotomorphogenesisLight Absorption & Photomorphogenesis Light absorption occurs like an antenna collects Light absorption occurs like an antenna collects

radio wavesradio waves Radiant energy is collected and quickly transferred Radiant energy is collected and quickly transferred

to processingto processing Energy is processed to perform more chemical Energy is processed to perform more chemical

reactions, or synthesize plant nutrientsreactions, or synthesize plant nutrients


Light can be transferred in one-millionth of a one-Light can be transferred in one-millionth of a one-millionth secondmillionth second

Photosynthesis is unique because it can trap this Photosynthesis is unique because it can trap this energy very effectively and quickly stabilize it energy very effectively and quickly stabilize it before it escapes in another formbefore it escapes in another form

PhotomorphogenesisPhotomorphogenesis is the process of is the process of converting these collected energy molecules and converting these collected energy molecules and fixated carbon dioxide and converted into other fixated carbon dioxide and converted into other molecules: proteins, fats, etc.molecules: proteins, fats, etc.

Carbon dioxide fixation in the plant occurs w/ the Carbon dioxide fixation in the plant occurs w/ the enzyme enzyme ribulose phosphate carboxylaseribulose phosphate carboxylase


As the amount of this enzyme increases, or works more As the amount of this enzyme increases, or works more efficiently, plant production is increasedefficiently, plant production is increased

PhotoperiodismPhotoperiodism Response to day lengthResponse to day length Example response to day length is floweringExample response to day length is flowering Plants can be divided into 3 categories based Plants can be divided into 3 categories based

on their preferences for flowering initiationon their preferences for flowering initiation Long-day, Short-day, and Day-neutralLong-day, Short-day, and Day-neutral Actual response is to amount of uninterrupted nightActual response is to amount of uninterrupted night


Flowering will not be affected by short periods Flowering will not be affected by short periods of dark during the dayof dark during the day

Flowering will be inhibited by short periods of Flowering will be inhibited by short periods of light during the nightlight during the night

By understanding photoperiod needs, we can By understanding photoperiod needs, we can sometimes manipulate flowering in plantssometimes manipulate flowering in plants What are some plants that we might do this with?What are some plants that we might do this with?

Long and short-day varieties of some plants Long and short-day varieties of some plants have been developed to take advantage of have been developed to take advantage of different day lengthsdifferent day lengths Example? Example?


Artificial IlluminationArtificial Illumination Looks the same, but quality variesLooks the same, but quality varies Can be heavy to some colors of the spectrumCan be heavy to some colors of the spectrum May need to mix lights to maximize growth w/ May need to mix lights to maximize growth w/

artificial lightartificial light Light Color & Plant GrowthLight Color & Plant Growth

Light quality refers to color and wavelength Light quality refers to color and wavelength reaching the plant surfacereaching the plant surface

Red & blue light best for plant growthRed & blue light best for plant growth Green light not beneficial because the plant Green light not beneficial because the plant

reflects itreflects it


Red and blue light will encourage floweringRed and blue light will encourage flowering Fluorescent lights are high in blue light and Fluorescent lights are high in blue light and

encourage leafy growthencourage leafy growth Good for starting seedlingsGood for starting seedlings Most commercial grow lights are fluorescent w/ a mixture Most commercial grow lights are fluorescent w/ a mixture

of red and orangeof red and orange

Incandescent lights are high in red and orange, but Incandescent lights are high in red and orange, but may be too hotmay be too hot

Growing Plants Under Artificial LightGrowing Plants Under Artificial Light Light most essential factor for indoor or Light most essential factor for indoor or

greenhouse plant growthgreenhouse plant growth


Grow and time of activity depends on duration of Grow and time of activity depends on duration of lightlight

Three aspects to consider:Three aspects to consider: IntensityIntensity

Influences manufacture of plant food, stem length, Influences manufacture of plant food, stem length, leaf color, floweringleaf color, flowering

Depends on proximity to the light sourceDepends on proximity to the light source Windows can effect greatly due to which direction Windows can effect greatly due to which direction

they face – southern exposures have most intense they face – southern exposures have most intense light, eastern/western have 40% less, northern have light, eastern/western have 40% less, northern have 80% less80% less

DurationDuration Only key if the plant if photosensitive for floweringOnly key if the plant if photosensitive for flowering Or if you want to manipulate floweringOr if you want to manipulate flowering


Low light intensity may be supplemented by Low light intensity may be supplemented by increasing durationincreasing duration

Illumination should not exceed 16 hrsIllumination should not exceed 16 hrs QualityQuality

Must be considered when using artificial lightsMust be considered when using artificial lights Select your light source carefully, and know what Select your light source carefully, and know what

color light it produces and how that will affect the color light it produces and how that will affect the plantplant

unit 5: temperature & light chapters 8 & 9. unit 5: temperature & light unit 5...

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