The Ohio State College Branch of Agriculture and Harvest Science H&CS 521 Nursery Crop Generation Light.

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Qualities of Light as They Relate to Growing Plants. Amount (Intensity) ... Vitality as Electromagnetic Radiation (EMR) that creates a ...
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The Ohio State University Department of Horticulture and Crop Science H&CS 521 Greenhouse Crop Production Light

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Characteristics of Light as They Relate to Growing Plants Quantity (Intensity) photosynthesis Quality (Wavelength - Color) photomorphogenesis Duration photoperiodism

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What is Light ? Vitality as Electromagnetic Radiation (EMR) that delivers a visual sensation

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The "Double Nature" of Light Particle light acting like a "bundle" of vitality PHOTONS - a molecule of light critical for plants. Photons are what the plant "sees" (detects) QUANTA-"bundle" or measure of vitality contained in a photon

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The "Double Nature" of Light Wave EMR can have short wavelengths  long wavelengths Energy is contrarily corresponding to wavelength Shorter wavelength = higher vitality

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Relationship amongst Energy and Wavelength ( )

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Photosynthetic & Visible Light Far-red

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How is Light (EMR) Generated? Everything with a temperature above total zero (- 273C) is emanating EMR The measure of vitality transmitted relies on upon the temperature Increase in temperature = increment in absolute vitality discharged Stephan-Boltzman Law

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Temperature versus Wavelength ( ) Temperature is conversely relative to wavelength Wein\'s Law: top  (wavelength) of EMR from an article is contrarily corresponding to temperature  can control shade of light by controlling temperature of an item.

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Pigments and Light Absorption Objects assimilate particular wavelengths Pigments are the chemicals in an item that retain particular wavelengths, giving that question its trademark C O L O R

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Light Reflected Green Yellow Orange Yellow Orange Black Red Biological Pigments

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Measuring Light Quantity Photometric Method Radiometric Method Quantum Method

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Photometric Method Based on the affectability of the human eye to distinguish electromagnetic radiation Very subjective Standard Unit = 1 foot flame (ftc) Amount of light emitted from 1 candle at a separation of 1 foot

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Light Absorption Human Eye versus Leaf Eyesight is not the most ideal approach to judge of the photosynthetic capacity of a light source on the grounds that the capacity to distinguish hues by our eyes is the inverse of leaf ingestion of hues for photosynthesis.

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Radiometric Method Measures electromagnetic radiation as far as aggregate vitality Standard Unit = W/m 2 Disadvantage wavelength is immaterial

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Quantum Method Measure of Photosynthetic Photon Flux (PPF) (400-700nm) Not measuring all  of whole range, it is measuring the measure of photosynthetic light Standard Unit = mol = (6.02 x 10 23 ) photons = mol = (6.02 x 10 17 ) photons Best approach to quantify light in the nursery since plants are "tallying" photons that they ingest.

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Light Intensity Directly Effects: 1. Photosynthesis plants are photon "counters"- photosynthetic yield is straightforwardly identified with photons consumed CO 2 + H 2 O + Light Energy  (CH 2 O) + O 2 2. Stature (stem development) 3. Improvement (blooming)

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What Limits Light Availability? Time of Year (season)* Latitude Time of Day Cloud spread (diminishes accessibility 3-6x) *Also decides length of day which impacts light accessibility Sun edge is affected by these variables and sun point decides light accessibility

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 Angle of Light and Intensity Lambert\'s cosine Law As you change the edge of rate ( ), the power of a light pillar will diminish as the edge of occurrence declines The lessening continues into the measure of light that goes through the nursery covering.

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Angle of Incidence 90 o is the point at which transmission force happens As the edge of the sun hitting the nursery rooftop increments to 90 o , light transmission into the nursery increments. When all is said in done, the higher the sun is in the sky, the more prominent the transmission into the greenouse. Low sun edge in the winter alongside short days drastically lessen light levels in the nursery amid that time.

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Time of Year

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Cloud Cover

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An overcast day in May gives more photosynthetic light than a crisp morning in December, for the most part in light of the term of the light time frame.

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Plant Physiology Under Low Light Intensity 1. Longer internodes, expanded stem lengthening 2. Leaves have bigger surface territory 3. More slender leaves and stems 4. More slender fingernail skin 5. One layer of palisade cells All are adjustments to expand photosynthesis

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Sun versus Shade Leaf Sun Shade

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Guess which plants haven\'t seen the light yet. Notice that both Easter lilies are blossoming.

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Light Quality Controls Photomorphogenesis (plant improvement and structure) Mediated by phytochrome (protein shade) red light retaining structure (Pr) FR light engrossing structure (Pfr) Forms are photoinconvertible, contingent upon the which sort of light is assimilated

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Light Quality RED Pr Pfr FR both structures actuate plant reactions reaction relies on upon which structure is prevailing

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Hard to realize that FR is available Humans can\'t sense it

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FR box has 5X more vitality than R box Red

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Plant Growth Response to Low R:FR ( R < FR by and large < 1:1 ) Low R:FR can come about because of increment in FR or lessening in Red and is shown by: 1. Lengthened internodes (extending) 2. Lessened sidelong spreading 3. Stretched petioles 4. Bigger, more slender leaf cutting edges 5. Littler aggregate leaf territory (because of lower quantities of leaves 6. Decreased chlorophyll amalgamation

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Plant Growth Response to High R:FR ( R > FR (for the most part > 1:1) ) High R:FR can come about because of lessening in FR or increment in Red and is demonstrated by 1. Diminished internode length 2. Expanded sidelong spreading 3. Shorter petioles 4. Thicker, littler leaves 4. More noteworthy aggregate leaf territory 5. Expanded leaf chlorophyll (darker green)

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R:FR is >1:1 Reduced internode length (short stems) Increased parallel spreading Shorter petioles Thicker, littler leaves Greater aggregate leaf zone Green (expanded chlorophyll) R:FR is <1:1 Elongated internodes (extending) Reduced horizontal stretching Elongated petioles Larger, more slender Smaller aggregate leaf zone (because of lower quantities of leaves) Reduced chlorophyll combination Which of the above would be the more solid, tastefully satisfying (attractive) plants?

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Can you tell which plant in every photo was developed with R>FR?

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Shade Avoidance Response Leaves firmly retain red and blue light The nearer plants are to a neighboring plant: less red light accessible for assimilation still have almost all FR light present in view of FR is transmitted and reflected however not consumed

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Shade Avoidance Response Phytochrome reacts to the nature of light inside the overhang of swarmed plants Mechanism by which plants can tell how close neighboring plants are and out-seek accessible space

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In thick shelters the prevailing type of phytochrome is Pr (which means it has ingested FR) Pr structure inspires shade shirking reaction

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Effects of Leaves on Light Reflection, Absorption, and Transmission

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Other Phytochrome Responses

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End of Day Response

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End of Day Response Plant reaction to the adjustments in the proportion of Red/FR light As day advances, more prominent shot of dispersing light in environment on account of lower sun point Shorter  have more prominent likelihood of dissipating At end of day, least Red/FR proportion for the day red light scattered significantly more than FR

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End of Day (EOD) Response

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EOD - essential in timing of photoperiodic blossoming

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Photoperiodism Duration of the Light Period As an aftereffect of regular changes in daylength, plants have developed frameworks to guarantee reasonability of seeds: -security before winter -agree with the blustery/dry seasons Photoperiodism - plant capacity to distinguish and react to day length

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Photoperiodic Response Short Day Plant (SDP) - bloom when the day length is not exactly the Critical Day Length Long Day Plant (LDP)- bloom when the day length is more prominent than the Critical Day Length Day Neutral - blossom without appreciation to day length

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Photoperiodic Response

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Photoperiodic Regulation Plants really measuring NIGHT length That implies that amid short day times of the year by hindering or part a taxing night with a moderately short photoperiod the plant sees a short night and taxing day impact despite the fact that the common day length has not changed

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Classes of Photoperiodic Plants Obligate - plant that must completely meet the day length prerequisite to bloom Facultative - plant that will blossom under most photoperiods yet will blossom most promptly when the photoperiodic necessity is met

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Understanding Photoperidism Allows year-round generation of photoperiodic plants Prior to disclosure, mums developed for fall deals Carnations developed for spring & early summer Same thing for other SD and LD plants now developed year-round

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Temperature Interaction Critical Daylength is Often Temperature Dependent SDP - as temp. builds, CDL diminishes (requires shorter days than typical) Mums Poinsettias LDP - as temp. diminishes, CDL diminishes (days don\'t need to be the length of typical) Fuchsia Spinach

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Note: the idea of short/taxing day is not constrained to 12 hrs. day/night. The basic dim period for a short day plant may just be 8 hrs. (16 hrs.light), yet in the event that it doesn\'t bloom when the night is any shorter than that, it is still a short day plant, despite the fact that it blossoms when the day length is 16 hrs. .:

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