Types of Lights for Indoor Garden (HPS Lamps or CFLs?)
During photosynthesis, chlorophyll absorbs energy from light radiation and uses it to synthesize carbohydrates from carbon dioxide and water.
Chlorophyll is a green pigment found in green plants, cyanobacteria, and some algae. Chlorophyll belongs to photosynthetic pigments along with phycobilins and carotenoids, which, however, have a different colour and absorb energy from a different part of the visible light spectrum. Chlorophyll is green because it absorbs the blue and red parts of the light spectrum and reflects the rest. This makes it appear green to us and gives the basic colour to all photosynthesizing plants.
Figure 2: Absorption spectrum of chlorophyll a and b
Several types of chlorophylls participate in photosynthesis; in plants, the most well-known are A and B. Other pigments involved in photosynthesis are carotenoids (which also play an important role in the plant's movement towards light). Chlorophylls absorb wavelengths of red (660 nm) and blue (440 nm) light. Green to yellow remains unused due to the green colour of chlorophyll, as chlorophyll reflects it.
The maximum efficiency of photosynthesis is in the area of red and blue radiation. Some light source manufacturers have utilized this action spectrum to develop and produce special linear or compact fluorescent lamps and discharge lamps designed for plant lighting. In the spectrum of these lamps, the green-yellow area is strongly suppressed, so the emitted light is purple and contributes to photosynthesis with high efficiency.
Function of Blue Light
In addition to photosynthesis, the plant uses blue light for phototropism – the plant distributes growth hormones appropriately and adapts its shape to the intensity and direction of precisely this radiation, so that it can use the radiation efficiently. Furthermore, stomata opening occurs according to blue radiation.
Red Light Effect
Plants utilize this spectrum both for photosynthesis and for stem elongation growth (stretching towards the sun). Here, the plant uses the ratio of radiation intensities at wavelengths of 660 (red)/735 (far red) nm. From the chlorophyll absorption curve (Figure 1), it is visible that the plant cleverly uses the sharp edge of this curve. If a plant is shaded by another plant, due to the absorption of red radiation by the chlorophyll of the shading plant, minimum red radiation reaches the plant, but sufficient far red radiation does, and the plant begins to elongate. Even if the plant has sufficient artificial lighting and far red predominates, the plant "stretches" upward believing it is shaded. With the opposite ratio, the plant grows slowly in height. Therefore, it is good to have the ratio of these radiation components balanced (similarly to solar radiation).
Artificial lighting is used for plants in cases where there is either a lack of natural daylight, or additional lighting is needed. For example, in winter months when daylight is insufficient for the desired plant growth. They are therefore used to extend the daytime period so plants receive the required light. Lack of light causes plants to slow their growth and develop disorders, which manifest for example in excessive elongation, thin stems, irregular coloring, etc.
Artificial lighting with fixtures to support plant growth demonstrably causes their proper growth and development, helps extend the flowering period and increases crop yield. Artificial lighting attempts to provide a light spectrum similar to the solar radiation spectrum or to supply a spectrum that is adapted to the needs of cultivated plants. Natural outdoor conditions are mimicked by various colors, temperatures and spectral outputs from artificial lighting, as well as by changes in lamp brightness intensity. Depending on the type of plant being grown, the cultivation phase (e.g., germination/vegetative phase or flowering/fruiting phase) and the length of day and night periods (light and dark) required by plants, specific spectrum ranges, luminous efficiency and color temperatures are suitable for use with particular plants and time periods.
Light Sources for Indoor Plant Cultivation
For indoor plant cultivation, it is necessary to use artificial lighting, which is a complete assembly that converts electrical energy into light.
The most widespread type of lighting is the use of high-pressure discharge lamps, which require a ballast for their operation, and additionally a socket and reflector.
The same is required when growing under compact fluorescent lamps, which are commonly known as fluorescent tubes or technically as CFL lamps. Some CFL lamps already have the ballast built into their body, so you will only need a reflector with a socket.
The last option is LED lighting modules, which are complete and you just need to plug them in.
When choosing artificial lighting, you can monitor a whole range of indicators. Light sources must meet the needs of plants both in terms of light intensity and the spectral composition of emitted radiation. Light is primarily a source of energy for photosynthesis, which ensures plant growth. This, as well as all other photobiological processes in plants, depend on the wavelengths of absorbed radiation.
In terms of spectrum, growers will be interested in whether the lighting is intended for green plants or for flowering plants. Accordingly, you choose lighting either for growth, for flowering, or for both.
Plant life processes are not determined only by photosynthesis, but also by other activities. These activities are considerably less energy-demanding. This primarily concerns photomorphogenesis, which influences the formation of shape and arrangement of functional plant organs and is supported mainly by the blue part of the spectrum. In some plants, especially tropical or mountain species, this activity extends into the ultraviolet radiation range. With insufficient blue light, plants become elongated, stem internodes are far apart, leaves are smaller and have a lighter colour. Another activity is phototropism, which influences the direction of growth of above-ground and underground plant parts (above-ground parts turn towards light, underground parts in the opposite direction). In all flowering plants, photoperiodism is of great importance, which is influenced especially by the long-wave part of the spectrum (red and far-red). It affects induction processes, namely bud formation and flower development. In some flowers, bud induction depends on day length. Long-day plants bloom in long days, short-day plants conversely in short days.
Lighting for Indoor Growing
Figure 3: LED lights create artificial environments for growing plants and vegetables and thanks to their high efficiency, they generate almost no heat compared to warm incandescent bulbs or halogen bulbs
Energy-saving lights or sodium lamps?
Energy-saving lamps ensure low energy consumption. Lamp installation is easy. The light spectrum of energy-saving lamps for growth and flowering is similar to that of discharge lamps. Energy-saving lamps are suitable for spaces where excess heat is a problem and can be hung low above plants at a height of approximately 30 cm.
Discharge lamps are not designed for direct connection to the mains. To assemble the lighting, you need a special ballast that matches the wattage, a socket, and a suitable cable. Discharge lamps come in grow, bloom, or combined light spectrum versions. Grow lamps – blue and white light. Bloom lamps – red-yellow light. Combined lamps – red, yellow, and a portion of blue spectrum.
Linear Fluorescent Tubes – For Growth and Rooting
Figure 4: Linear Fluorescent Tubes
A linear fluorescent tube is a long glass tube with airtight bases at both ends, through which electrodes are inserted into the tube. Inside is a mixture of mercury vapour and argon. Fluorescent tubes emit cool blue-white or red light. Blue-white is particularly suitable for the growth phase of plants. When rooting plants, growers achieve good results with fluorescent tubes producing red light. Fluorescent tubes can be used for pre-growing plant seedlings or for growing herbs (such as basil, chives, or parsley). Because linear fluorescent tubes have lower power output, they are particularly suitable for shorter plants. They may not be sufficient for taller ones.
Properties:
- high efficiency of converting electrical energy into light, reaching up to 104 lm/W with high-frequency power supply, while maintaining a high general colour rendering index Ra of up to 80,
- suitable geometric parameters, allowing the construction of material-efficient luminaires with simple optics and the possibility to assemble them into aesthetic continuous light strips or large surfaces,
- very wide range of wattages from 4 to approximately 200 W,
- very wide range of emitted light colours, characterized by correlated colour temperature from 2,700 to 17,000 K,
- special types can achieve Ra up to 98 with very good luminous efficacy,
- highly productive production lines with capacity reaching up to 4,000 units/h, with high manufacturing process yield; this results in consistently low prices for the basic range of fluorescent tubes,
- long lifespan, reaching more than 20,000 hours for some special types with good luminous flux stability throughout operation
Compact Fluorescent Lamps (Energy-Saving Lamps) – For Small to Medium Plants
Figure 5: Compact Fluorescent Lamp
Compact fluorescent lamps have 60 to 80% higher energy efficiency compared to standard traditional bulbs. The average lifespan of compact fluorescent lamps is more than ten times longer than that of traditional bulbs – compact fluorescent lamps approximately 6,000 to 20,000 hours, traditional bulbs approximately 1,000 hours. Quality compact fluorescent lamps designed for consumers have a colour rendering index Ra > 80.
Compact fluorescent lamps are traditionally manufactured with grow, bloom and dual spectrum. These lamps are so-called energy-saving lamps with output from 85W to 250W. The functioning of compact fluorescent lamps is practically identical to the functioning of linear fluorescent lamps, with the difference that the output of compact fluorescent lamps is higher than the output of linear fluorescent lamps. Compact fluorescent lamps with grow spectrum can be used for pre-growing seedlings, growing non-flowering plants or for the growth phase of flowering plants. Compact fluorescent lamps with bloom spectrum can then be used for the flowering phase of flowering plants. Compact fluorescent lamps with dual spectrum can be used for all types of plants at any stage of development. Because energy-saving lamps emit less heat, they can be installed in close proximity to plant tops. Therefore, they are also suitable for small or poorly ventilated spaces.
Features:
- smaller dimensions than linear fluorescent lamps
- higher output in a given space, but lower specific output compared to linear fluorescent lamps
- output ranges from 5 to 55W
- lamps have up to 80% lower consumption with the same amount of light
- six to fifteen times longer lamp lifespan, which represents an average lifespan of 6,000 hours up to 15,000 hours
- manufactured in many types and shapes
- excellent colour rendering of lamps Ra80
Fluorescent Lamps
Figure 6 Fluorescent Lamps
The basis of fluorescent lamp light is ultraviolet light invisible to the human eye, which is generated when electric current flows through inert gas. This ultraviolet light reacts with a special mixture of phosphors that covers the inner wall of the fluorescent tube. The invisible light is thus converted into usable white light. Fluorescent lamps require a special power source, called a ballast, which regulates the operating current of the lamp and supplies the appropriate voltage to ignite the discharge. Electronic ballasts have the same function as outdated magnetic ballasts, but unlike them, they operate at very high frequency. This eliminates disruptive flickering and noise while increasing output. Electronic ballasts can also be more easily designed to enable more stable and efficient lamp operation, light intensity adjustment, and interconnection of individual lighting elements within a network, allowing lighting to be controlled in a modern way.
Fluorescent tubes are an excellent solution for task lighting in study rooms, home offices, and other spaces where really bright light is needed. They last up to 20 times longer than traditional bulbs and have up to 80% lower energy consumption.
Tubes of various sizes can be used, from thirty centimeters to two and a half meters long, fitted into standard fluorescent light fixtures. With such lighting, plants can be grown in basements, storage rooms, or attics at almost the same rate as outdoors in midsummer. They are perfect for the growth phase. They are manufactured in wattages of 18W, 36W, and 54W. Due to their low wattage, they are more suitable for rooting cuttings or for illuminating lower parts of plants in both growth and flowering phases. A starter and ballast are also required for their connection, but in much lower wattages than "energy-saving bulbs".
Technical characteristics
- low-pressure mercury tubes
- low temperature of the light source allows tubes to be placed close to plants without risk of burning them
- high initial light output
- can be used with standard and high-frequency ballasts
- fully recyclable tubes, all components can be used in manufacturing new tubes
- green spot on the base indicates that the tube is recyclable
LED lights - for plant growth
Figure 7: LED lamp
LED lights for supporting plant growth are suitable for use primarily in botanical gardens, for plant breeding in garden greenhouses, in interiors for plant illumination, etc.
Cultivation lights from LEDs are characterized by one fundamental property. Semiconductor components can emit narrow-band monochromatic light. When combining diodes of different colors and regulating power, they allow mixing any light spectrum and dynamically changing it. Light quality can then be adapted to the needs of a specific species or developmental phase (vegetative phase, generative phase - flowering induction). The best contemporary automatic and appropriately expensive systems designed for greenhouses pamper crops by, for example, mimicking the color rendition of rays prevailing at sunrise and sunset. Easy installation and operation of the device, plug directly into a 220-240V socket. (No additional electrical power supply needed.) The light can be placed directly above plants, it does not emit any hot light or flickering. Expected lighting time 10 - 18 hours daily
Properties:
- extreme lifespan - 100,000 hours (more than 10 years of continuous operation),
- low power consumption,
- resistance to shocks, impacts, vibrations,
- minimal heat generation,
- controlled radiation characteristics,
- no infrared or ultraviolet radiation,
- high lifespan and almost zero failure rate,
- negligible electricity consumption costs per year,
- minimal or zero maintenance,
- possibility of frequent switching on and off,
- high resistance to damage and cold,
- colour diversity – white, red, blue, yellow, green,
- due to high efficiency, it generates almost no heat.
Sodium Lamps
Figure 8: Sodium lamp
Sodium lamps are light sources in which light is emitted mainly by sodium vapour with an operating partial pressure ranging from 3 to 60 kPa. The lamps are then classified according to wattage (70W, 100W, 150W, 400W, 600W, etc.), spectrum - growth, flowering, or combined spectrum and number of lumens. Compared to conventional bulbs, discharge lamps are characterised by very economical operation and emit an extremely large amount of radiation for their size. Sodium lamps feature double the conversion coefficient of electrical energy to photosynthetically active radiation energy compared to mercury lamps. Tubular sodium lamps combine high radiant output (up to 150lm/W) from a spectral energy distribution that appears most favourable for various types of indoor crops. Increasing the pressure of sodium vapour in the radiation focus allows spectrum expansion in the red and blue colours and a so-called continuous background over a wide wavelength range. The lamps are not designed for direct connection to the mains - they require a special ballast for operation. Growth lamps emit blue and white light, flowering lamps emit red-yellow light, and combined lamps emit red and yellow light with some blue spectrum content.
Sodium lamps are suitable for greenhouse lighting. They are ideal for supplementary lighting in horticulture as they stimulate plant assimilation and growth. This is particularly important for growing cut flowers, vegetables, houseplants and seedlings. For horticulture, this provides the following benefits: shorter growing times, healthier plants, influence on flowering time.
Features
- production of very intense light
- high luminous efficacy lm/W
- long lifespan
- stable output
- production of large amounts of heat, leading to the need for additional cooling equipment
- due to heat generation, the distance between the light source and plant tops must be monitored
- higher electricity consumption