Deutsch
Español (España, Alfabetización Internacional)
Nederlands
What Wavelengths and Colors do
To understand how your crops are going to react on different wavelengths and colors, you have to keep in mind that every crop and every growth stage requires an individual approach.
The amount of light affects the photosynthesis process in the plant.
This process is a photochemical reaction within the chloroplasts of the plant cells in which CO₂ is converted into carbohydrate under the influence of the light energy.
The spectral composition of the different wavelength regions (blue, green, yellow, red, far red or invisible e.g. UV or IR) is important for the grows, shape, development and flowering (photomorphogenesis) of the plant.
For the photosynthesis, the blue and red regions are most important.
The timing / light duration which is also called photoperiod is mainly affecting the flowering of the plants. The flowering time can be influenced by controlling the photoperiod.
Photosynthetic efficiency is mainly driven by chlorophyll a and b.
Chlorophyll a and b are mainly responsible for the photosynthesis and responsible for the definition of the area for the photosynthetically active radiation PAR.
The Photosynthetically active radiation (PAR) shows further photosynthetic pigments also known as antenna pigments like carotenoids - carotene, zeaxanthin, lycopene and lutein etc.
| Wavelength range [nm] | Photosyntesis | Further Effects | Further Effects | Further Effects |
|---|---|---|---|---|
| 200 – 280 | Harmful | |||
| 280 – 315 | Harmful | |||
| 315 – 380 | ||||
| 380 – 400 | Yes | |||
| 400 – 520 | Yes | Vegetative growth | ||
| 520 – 610 | Some | Vegetative growth | ||
| 610 – 720 | Yes | Vegetative growth | Flowering | Budding |
| 720 – 1000 | Germination | Leaf building and growth | Flowering | |
| > 1000 | Converted to heat |
The Phytochromes Pr (red) and Pfr (far red) are mainly influencing the germination, plant growth, leave building and flowering.
The phytomorphogenic effects are controlled by applying a spectrum with a certain mix of 660nm and 730nm in order to stimulate the Pr and Pfr phytochromes.
A typical application example for the use of 730nm: The shade escape reaction
One of the most obvious influence of far red light on a plant is the shade escape reaction.
Illumination with 660nm:
If the plant is illuminated mainly with 660nm it feels like illuminated in the direct sun and grows normally.
Illumination with 730nm:
If the plant is illuminated mainly with 730nm it feels like growing in the shadow of another plant that shades the sun light.Therefore the plant is reacting with an increased length growth to escape the shadow. This leads to taller plants but not necessarily to more bio mass.
Special potential of LEDs in floriculture lighting
Traditionally ornamental plants are of high economic importance. The Red and Far-Red light mediates the conversion of phytochromes which can control the triggers for flowering.
Illumination with 730nm:
The cycle from Pr to Pfr is initiated by red light of 660nm which represents daylight. During the night time, the Pfr is converted back to Pr. This back conversion can also be actively be influenced by 730nm far red light.This enables a perfect control of the flowering timing independent of the seasons.
Control of the flowering due to control of the critical day length by using any light
Due to the influence of the Pr and Pfr ratio the flowering can be controlled to adjust the timing to environmental or seasonal requirements.
| Plant | Radiation source | Effect on plant physiology |
|---|---|---|
| Indian mustard (Brassica juncea L.) Basil (Ocimum gratissimum L.) | Red (660 and 635 nm), LEDs with blue (460 nm) | Delay in plant transition to flowering as compared to 460 nm + 635 nm LED combination |
| Cabbage (Brassica olearacea var. capitata L.) | Red (660 nm) LEDs | Increased anthocyanin content |
| Baby leaf lettuce (Lactuca sativa L. cv. Red Cross) | Red (658 nm) LEDs | Phenolics concentration increased by 6% |
| Tomato (Lycopersicum esculentum L. cv. MomotaroNatsumi) | Red (660 nm) LEDs | Increased tomato yield |
| Kale plants (Brassica olearacea L. cv Winterbor) | Red (640 nm) LEDs (pretreatment with cool white light fluorescent lamp) | Lutein and chlorophyll a, b accumulation increased |
| White mustard (Sinapsis alba), Spinach (Spinacia oleracea), Green onions (Allium cepa) | Red (638 nm) LEDs with HPS lamp (90 μmol m-2 S-1), total PPF (photosynthetic photon flux) maintained at 300 μmol m-2 S-1 | Increased vitamin C content in mustard, spinach and green onions |
| Lettuce (Lactuca sativa), Green onions (Allium cepa L.) | Red (638 nm) LEDs and natural illumination | Reduction of nitrate content |
| Green baby leaf lettuce (Lactuca sativa L.) | Red (638 nm) LEDs (210 μmol m-2 S-1) with HPS lamp (300 μmol m-2 S-1) | Total phenolics (28.5%), tocopherols (33.5%), sugars (52.5%), and antioxidant capacity (14.5%) increased but vitamin C content decreased |
| Red leaf, green leaf and light green leaf lettuces (Lactuca sativa L.) | Red (638 nm) LEDs (300 μmol m-2 S-1) with HPS lamp (90 μmol m-2 S-1) | Nitrate concentration in light green leaf lettuce (12.5%) increase but decreased in red (56.2%) and green (20.0%) leaf lettuce |
| Green leaf ‘Lolo Bionda’ and red leaf ‘Lola Rosa’ lettuces (Lactuca sativa L.) | Red (638 nm) LEDs (170 μmol m-2 S-1) with HPS lamp (130 μmol m-2 S-1) | Total phenolics and α-tocopherol content increased |
| Sweet pepper (Capsicum annuum L.) | Red (660 nm) and farred (735 nm) LEDs, total PPF maintained at 300 μmol m-2 S- 1 | Addition of far-red light increased plant height with higher stem biomass |
| Red leaf lettuce ‘Outeredgeous’ (Lactuca sativa L.) | Red (640 nm, 300 μmol m-2 S-1) and farred (730 nm, 20 μmol m- 2 S-1) LEDs. | Total biomass increased butanthocyanin and antioxidant capacity decreased |
| Red leaf lettuce ‘Outeredgeous’ (Lactuca sativa L.) | Red (640 nm, 270 μmol m-2 S-1) LEDs with blue (440 nm, 30 μmol m-2 S-1) LEDs | Anthocyanin content, antioxidant potential and total leaf area increased |
| Tomato seedlings ‘Reiyo’ | Red (660 nm) and blue (450 nm) in different ratios | Higher Blue/Red ratio (1:0) caused reduction in stem length |
| Plant | Radiation source | Effect on plant physiology |
|---|---|---|
| Cherry tomato seedling | Blue LEDs in combination with red and green LEDs, total PPF maintained at 300 μmol m-2 S-1 | Net photosynthesis and stomatal number per mm² increased |
| Cabbage (Brassica olearacea var. capitata L.) | Red (660 nm) LEDs | Increased anthocyanin content |
| Seedlings of cabbage (Brassica olearaceavar. capitata L.) | Blue (470 nm, 50 μmol m-2 S-1) LEDs alone | Higher chlorophyll content and promoted petiole elongation |
| Chinese cabbage (Brassica camprestis L.) | Blue (460 nm, 11% of total radiation) LEDs with red (660 nm) LEDs, total PPF maintained at 80 μmol m-2 S-1 | Concentration of vitamin C and chlorophyll was increase due to blue LEDs applicatio |
| Baby leaf lettuce ‘Red Cross’ (Lactuca sativa L.) | Blue (476 nm, 130 μmol m-2 S- 1) LEDs | Anthocyanin (31%) and carotenoids (12%) increased |
| Cucumber ‘Bodega’ (Cucumis sativus ) and tomato ‘Trust’ (Lycopersicon esculentum) | Blue (455 nm, 7-16 μmol m-2 S- 1) LEDs with HPS lamp ( 400- 520 μmol m-2 S-1) | Application of blue LED light with HPS increased total biomass but reduced fruit yield |
| Transplant of cucumber ‘Mandy F1’ | Blue (455 and 470 nm, 15 μmol m-2 S-1) with HPS lamp (90 μmol m-2 S-1) | Application of 455 nm resulted in slower growth and development while 470 nm resulted in increased leaf area, fresh and dry biomass |
| Plant | Radiation source | Effect on plant physiology |
|---|---|---|
| Red leaf lettuce (Lactuca sativa L. cv Banchu Red Fire) | Green 510, 520 and 530 nm LEDs were used, and total PPF was 100, 200 and 300 μmol m-2 S-1 respectively | Green LEDs with high PPF (300 μmol m-2 S-1) was the most effective to enhance lettuce growth |
| Transplant of cucumber ‘Mandy F1’ | Green (505 and 530 nm, 15 μmol m-2 S-1), LEDs with HPS lamp (90 μmol m-2 S-1) | 505 and 530 nm both resulted in increased leaf area, fresh and dry weight |
| Red leaf lettuce (Lactuca sativa L. cv Banchu Red Fire) | Green 510, 520 and 530 nm LEDs were used, and total PPF was 100, 200 and 300 μmol m-2 S-1 respectively | Green LEDs with high PPF (300 μmol m-2 S-1) was the most effective to enhance lettuce growth |
| Tomato ‘Magnus F1’ Sweet pepper ‘Reda’ Cucumber | Green (505 and 530 nm, 15 μmol m-2 S-1) LEDs with HPSlamp(90 μmol m-2 S-1) | 530 nm showed positive effect on development and photosynthetic pigment accumulation in cucumber only while 505 nm caused increase in leaf area, fresh and dry biomass in tomato and sweet pepper |
| Transplant of cucumber ‘Mandy F1’ | Green (505 and 530 nm, 15 μmol m-2 S-1), LEDs with HPS lamp (90 μmol m-2 S-1) | 505 and 530 nm both resulted in increased leaf area, fresh and dry weight |
| General purpose – high efficiency |  | |||
|---|---|---|---|---|
| Type | Wavelength | mW Ratio | ||
| LD Cxxx | 450nm | 23% | ||
| LH Cxxx | 660nm | 77% | ||
| The highest efficacy of μmol/J from the spectrum can be achieved by using the 660nm Red LEDs combined with some 450nm Blue LEDs to maintain a reasonable ratio between the wavelengths. | ||||
| Vegetative Growth |  | |||
|---|---|---|---|---|
| Type | Wavelength | mW Ratio | ||
| LD Cxxx | 450nm | 50% | ||
| LH Cxxx | 660nm | 50% | ||
| Especially for growth of the leafy green vegetable plants the vegetative growth ratio is used to achieve fastest growth where visible assessment of plant health is not important. | ||||
| Best for seedlings |  | |||
|---|---|---|---|---|
| Type | Wavelength | mW Ratio | ||
| LD Cxxx | 450nm | 75% | ||
| LH Cxxx | 660nm | 25% | ||
| A high blue content in the spectrum is recommended for growth of the seedlings. | ||||
Loading