Noter om dyrkning af Rhododendron under
LED-vækstlys.
”En glad amatørs pseudovidenskabelige
research”
Min interesse for emnet startede, da jeg
i radioen hørte, at forskere i Århus havde dyrket grønsager uden brug af andet
lys end LED-lys (= light emitting diode). Vi kender efterhånden LED-lys fra
mange områder i hverdagen. Hvorfor er det interessant? Fordi energiforbruget ved LED-lys er langt mindre end ved andre former for
kunstige lyskilder. Samtidig er levetiden længere, efter sigende helt op til
50.000 timer. Det er væsentligt længere end lysstofrøret, og anskaffelsesprisen
er efterhånden på et rimeligt niveau. Tænk hvis man kan mere end halvere sin
udgift til kunstlys!
Planternes stofskifte, fotosyntesen, er
betinget af følgende elementer:
1)
Vand (H2O) og næringssalte
som er i vandet eller tilsættes som gødning
2)
Kuldioxid fra luften (CO2), f.eks.
i form af vores udåndingsluft. Dette bekræfter vigtigheden af, at vi snakker
med vore små kæledægger
3)
Sollys, evt. kunstlys fra
lysstofrør eller LED
Hvis disse betingelser er opfyldt i rette
forhold, dannes der glukose (sukker), som er det ”protein”, der er basis for
plantevæksten. Som en bonus for os afgiver planterne ilt gennem bitte små
spalteåbninger på undersiden af bladene. Gennem de samme åbninger optager planterne
CO2 fra luften. Spalteåbningerne er også de organer, der regulerer
fordampningen fra bladene, den såkaldte transpiration.
Når vi
Rhodo-dyrkere i den nordlige del af Europa i løbet at efteråret og vinteren
starter vores prikle- eller spirekasser, er vi afhængige af kunstlys, da der
simpelthen er for lidt sollys til at opretholde fotosyntesen. Jeg må skynde mig
at sige, at det kan lade sig gøre uden brug af kunstlys. Men for den optimale
løsning kræves ekstra lys. Gert Forum Petersen lavede i sin tid en
samlemappeside om brugen af kunstlys, baseret på lysstofrør. Der kan man blandt
andet læse om de lysfrekvenser, som planterne bruger til fotosyntesen. Dagslyset
består af et spektrum af forskellige bølgelængder, fra kortbølget violet-blåt
til langbølget rødt. Ikke alle
bølgelængder er essentielle for plantevækst. Især den røde og blå del af
spektret har betydning. Lysets bølgelængder måles i nanometer (nm). Rødt lys (620-720
nm) driver den primære fotosyntese og fremmer blomstring og frøsætning. Blåt
lys (400-450 nm) fremmer primært den vegetative vækst, og hindrer planterne i
at strække sig. Blåt lys giver altså kompakte planter. Det skal dog
understreges, at den optimale lysblanding varierer alt efter planteart.
De lysstofrør
vi hidtil med stor succes har anvendt, afgiver også lys af bølgelængder, som
planterne ikke har brug for. LED-lys giver os mulighed for at selektere og sammensætte
de frekvensområder, som er vigtige for plantevækst. Forskningen tyder på, at
den ideelle balance er 92 % røde dioder og 8 % blå. Dette er en
gennemsnitsbetragtning, som varierer alt efter de plantearter, der dyrkes.
Optimalfordelingen for rhododendron er ikke tilgængelig på nettet og varierer
formentlig fra art til art. Det er her jeg som den nysgerrige amatør er begyndt
at prøve mig frem.( Et par timers blåt lys, fra morgenstunden, inden man
slår over i et rødt eller blandet rødt og blåt lys, øger planternes optagelse
af CO2 yderligere)
Jeg startede
med at anskaffe et par 7-Watt LED-pærer, indeholdende 7 lyskilder a` 1 Watt
fordelt på 4 røde (620 nm) og 3 blå (460 nm). Dette lys blev anvendt til den
ene af 2 ens frøportioner. Den anden frøportion blev belyst af et 18 Watts
lysstofrør farve 83. Lyskildens højde over gromediet blev justeret, så
lysstyrken målt i Lumen var ens for begge bede. Forsøget var i gang!
Mine første
iagttagelser tyder på, at spiringen under LED-lyset er hurtigere og bedre. Dog
fik planterne rødlige blade, hvilket kunne tyde på dårlig rodudvikling. Ved
eftersyn så rødderne dog fine ud. Faktisk var de langt bedre udviklet end på
planterne under lysstofrøret. Nu hvor planterne er priklet om, bliver det
spændende at følge den videre vækst.
Mine
kælderforsøg fortsætter, og jeg skal også afprøve LED-lys på både stiklinger og
podninger.
Jeg vil også
arbejde videre med sammensætningen af lyset. I Tyskland (via nettet) har jeg
købt LED lamper med 165 røde, og 65 blå dioder, på hver 0,06 Watt. Jeg har også
et par hjemmelavede lamper, liggende på arbejdsbordet. Det giver uendelig mange
variationsmuligheder når man opbygger sine egne LED-lamper.
Fakta i denne notits stammer fra div. artikler på internettet. Det er stadig
her, den største viden ligger.
OBS!
Jeg er opmærksom på at LUX ikke er korrekt måleenhed for planter. Mit budget afholder mig fra at købe optimalt måleudstyr.
OBS!
Jeg er opmærksom på at LUX ikke er korrekt måleenhed for planter. Mit budget afholder mig fra at købe optimalt måleudstyr.
Mikke Jørgensen
An amateur’s research
on the use of LED lights in rhododendron propagation.
Mikkel Jørgensen
Hvidovre, Denmark
(modified from the RhodoNyt 2012 (4), the magazine of the
Danish ARS Chapter; written in Danish and translated by the author)
My interest in this subject started when I heard on the
radio that researchers in Aarhus, Denmark, had grown vegetables without the use
of natural lightning, using only LED (light emitting diode) light. LED lights are
now commonly used in many ways in daily life, and this is interesting because
energy consumption by LED lights is much less than with other forms of
artificial light. Their lifetime is also longer, reportedly up to 50,000 hours,
significantly longer than fluorescent tubes. Finally, their purchase price is now
at a reasonable level, allowing a reduction of more than halve the expense for
artificial lighting!
Plant metabolism, i.e., photosynthesis, is subject to the
following elements:
1) water, and nutrients which are added as fertilizer;
2) carbon dioxide from the air, such as is produced from of our breath, confirming the importance of the need to talk to our little darlings; and
3) light, from either the sun or if necessary, artificial light from incandescent, fluorescent or LED lights.
If these elements are provided in the right combination, glucose is formed, the energy source for plant growth. As a bonus for us, plants release oxygen as well!
When rhodo growers in northern Europe start plants during the fall and winter in our our prickle or germination boxes, we typically utilise artificial light, as there simply is not enough sunlight to sustain optimal photosynthesis then. I must hasten to say that propagation can be done without the use of artificial light but for optimal growth, extra light is required. Gert Forum Petersen, a former member of Danish chapter and an ARS Silver Medal Awardee, discussed.
1) water, and nutrients which are added as fertilizer;
2) carbon dioxide from the air, such as is produced from of our breath, confirming the importance of the need to talk to our little darlings; and
3) light, from either the sun or if necessary, artificial light from incandescent, fluorescent or LED lights.
If these elements are provided in the right combination, glucose is formed, the energy source for plant growth. As a bonus for us, plants release oxygen as well!
When rhodo growers in northern Europe start plants during the fall and winter in our our prickle or germination boxes, we typically utilise artificial light, as there simply is not enough sunlight to sustain optimal photosynthesis then. I must hasten to say that propagation can be done without the use of artificial light but for optimal growth, extra light is required. Gert Forum Petersen, a former member of Danish chapter and an ARS Silver Medal Awardee, discussed.
the use of artificial light, based on fluorescent lamps,
and among other things, about the frequencies of light that plants use for photosynthesis.
Daylight consists of a spectrum of different wavelengths, from short wavelength
violet-blue to long wavelength red. Not all light wavelengths are essential for
plant growth, as this is influenced by the types of pigments present in plant leaves.
The red and blue parts of the spectrum are especially important. Light
wavelengths are measured in nanometers (nm) and red light (620-720 nm) triggers hormones in plants that increase flowering and budding, but
plants cannot grow with red light alone. Red light stimulates flowering and
foliage growth, but too much red light will cause a plant to become spindly.
Blue light (400-450 nm) regulates the rate of a plant’s growth
and many plant responses, including stomata opening and phototropism. A
plant's moisture loss is primarily influenced by stomata and blue light
controls stomata behavior (openings on or beneath the surface of the leaves
that control the rate of gas and water exchange), and thus the amount of water
a plant retains or expels. Phototropism is the definition of a plant's response
to light; the stems grow up toward the light and the roots grow down, away from
the light. Blue light thus helps determine the compactness
plants, although it should be emphasized that optimum light conditions varies with
plant species.
The lamps we have successfully used to date
also give light in wavelengths that plants do not need. LED lights allows us to
select and assemble the light wavelength ranges that are most important for
plant growth. General research (http://www.easygrowled.com/Info.aspx,
http://www.bbbled.com/news/41.html, http://www.newenergyresearch.net/growing_plants_with_leds.php) suggests that the ideal average balance for most plant
growth is 92% red and 8% blue LEDs. However, the optimal wavelength distribution
for rhododendrons is not available and probably varies from species to species.
This is where, I as a curious amateur, began to test and try out various LED combinations.
First I bought a pair of seven watt LED fixtures
containing seven light sources of one watt each: four red (620 nm) and three
blue (460 nm). This light was applied to one of two identical plantings of rhododendron
seeds, with the second batch being illuminated by an 18 watt fluorescent tube
(warm white 830; digit “8” is the Colour Rendering, and “30”
is the colour temperature
= 3000 K). Lamp height above the medium was
adjusted to make a 2800 lumen brightness for both plantings. The trial was in
progress, and the results after five months are reported here!
My initial observations suggested that germination with LED lights was faster and better. However, given the seedling’s reddish leaves, there was perhaps too low a light intensity. The roots looked fine and were more developed than with the the plants under fluorescent light. The plants have now been transferred into growing medium, and I am following further growth characteristics.
I will also be testing the LED lights on both cuttings
and graftings, and will experiment further on the desirable composition of the
light. I have recently bought LED light fixtures with 165 red and 65 blue LEDs,
each of 0.06 watt. I also have a couple of homemade lamps, and there are endless
variation possibilities when building your own LED fixtures. My newest creations
are made with 30 one-watt diodes: 20
one-watt 660 nm reds, four one-watt 610-630 nm reds, and six one-watt 450-455
nm royal blues. The diodes are mounted on a 0.5 m2 sheet of aluminum
to prevent overheating. My hope is to achieve a 40-50% power saving.
Mikkel Jørgensen
