How Limiting Factors Affect Plant Growth

Purchasing LED grow lights for your facility is an important step towards growing healthy plants. Illumitex LED fixtures are made to increase and maximize plant growth. Aside from the technology, growers need to be aware of certain factors that affect optimal plant growth.

Six Critical Resources
Plants require a balance of six critical factors in order to optimize growth— temperature, humidity, carbon dioxide, water, nutrients, and light. When growing in a controlled environment, growers can control these conditions to maximize their plants’ growth potential.

There are limits to a plant’s ability to utilize each parameter at any given time; overexposure to any one factor can be detrimental to plant health and growth rate. For example, fertilization allows the plant access to extra resources to increase growth rates but too many nutrients can be toxic, resulting in burned plant roots. Water is necessary, but if a plant is over-watered, the oxygenation of the root zone is reduced, killing the plant.

A common occurrence when replacing HID fixtures with LEDs is a decrease in room temperature because HID lamps emit more radiant heat than LEDs. If the temperature decreases in the growing environment, certain metabolic processes like photosynthesis may suffer. Therefore, growers should monitor and regulate the temperature of their environment when switching from HID to LED lights.

The Limiting Factor
Plants can only grow as much as the limiting factor will permit. Every factor must be balanced with one another to foster maximum growth. If a resource is limited, growth will be limited by that deficit. If carbon dioxide is the limiting factor, supplemental carbon dioxide applied to the environment will increase plants’ ability to photosynthesize until a different resource becomes limited. Illumitex’s mission is to ensure that light and the limiting factor is not wasted in any grow operation.

Dimming Allows Fine-Tuning
Illumitex uses precision optics to focus intense light on the plant canopy. Instead of raising and lowering the fixtures to adjust the intensity of light, dimming allows the same control without compromising the coverage over a given area.

Depending on the crop, plants require certain lighting conditions including duration, photoperiod, intensity, and specific wavelengths. Photosystems within the chloroplasts of a plant cell are the drivers of photosynthesis. They are activated by two main peaks, one in the red range and the other in the blue range. The F3 spectrum is optimal for all plants as it provides an appropriate ratio of peak absorption wavelengths of red and blue light.

In addition to understanding wavelength needs, it is important to know the optimal photoperiod or lighting duration that will optimize plant growth.

Daily Light Integral
Daily light integral (DLI) is the amount of light required by a particular crop over the course of a day. Photosynthetic photon flux density (PPFD) is the intensity of light at the plant canopy. Photoperiod, DLI, and PPFD are expressed in the following equation:
DLI = PPFD*photoperiod*.0036.

Once the duration of light and the target DLI value is determined, the equation can be solved for the light intensity needed.  If the intensity and DLI value is known, the equation can be solved for photoperiod.

Micro greens, leafy greens and herbs have a low light-intensity requirement. DLI values for these crops range from 6-17 mol/m2/day. They do not require a particular photoperiod but typically perform best at between 16-20 hours of light. At a maximum, light would supply a PPFD of roughly 260 umol/m2/s with a photoperiod of 16 hours. Keep in mind, although these are optimal lighting conditions, they will not be any more beneficial to plants if they are limited by another resource.

Non-photoperiod flowering vegetables require an intermediate amount of light intensity with DLI ranging from 8-18 mol/m2/day. If the photoperiod is 16 hours, the maximum intensity required would be approximately 310 PPFD.

Some specialty peppers and tomatoes require a substantial amount of light, requiring a DLI range of 14-20+ mol/m2/day.  The indicated crops would need approximately 350 PPFD for a 16 hour photoperiod.

The amount of light required for a growth system can be calculated in theory but actual light levels may be lower than expected due to limiting resources. The dimming feature of Illumitex fixtures is the solution to fine-tuning the light environment for maximum crop yields.

The Illumitex Solution
Illumitex offers a variety of horticultural fixtures, each designed for specific applications. To replace standard HID lighting, the NeoSol line is the solution. The NeoSol NS grow light is comparable to a 600W high intensity discharge fixture and the NeoSol DS is comparable to a 1000W HID fixture.

illumitex NeoSol™ DS

illumitex NeoSol™ DS

Eclipse Gen2 lights are useful in open bed and vertical farming scenarios. They can be spread apart at various distances to achieve appropriate light intensities and uniformity. For ease of wiring, they can be daisy-chained in different configurations.

illumitex Eclipse Gen2

illumitex Eclipse Gen2

The PowerHarvest W series is designed for indoor grow operations, either as sole-source (open-floor beds) or supplemental lighting (greenhouses). Options include wireless dimming, on/off, light schedules, and power and date monitoring control from a laptop computer, tablet or smart phone.

illumitex PowerHarvest™ W

illumitex PowerHarvest™ W

Illumitex’s dedicated team of horticultural scientists provide custom-tailored recommendations for every grow application. From retrofitting existing grow spaces to starting a new facility, Illumitex guides customers in the right direction for success every step of the way.

For more horticultural tips, tune in every Tuesday for #TipTuesday on Illumitex social media channels. http://illumitex.com/social