Growth regulation without chemistry

Growth regulation without chemistry

Blue light is the secret to success

Roses are red, violets are blue, it is said. But other plants can benefit from red and blue colours as well. Blue and red LED light have proven particularly effective when it comes to speeding production times and optimizing plants, a study on Osteospermum carried out by DGT by Senmatic and a Danish nursery shows.

From production of cuttings to breeding at propagation stations and further processing in the nurseries. There are multiple processes prior to the end consumer purchasing daisy flowers in their local stores. But the process can be accelerated by replacing chemical plant growth regulators (PGRs) with LED lighting. The faster production times in the nurseries free space for more plants to sell to the stores’ procurement team.

Study results: Faster production times with no use of chemistry

Results from the study with LED light as replacement for PGRs are convincing, but also surprising. In addition to greener foliage and more uniform plants, production times were optimized from a normal rate of 4-6 weeks from stick to onward sale for transplanting to 3-5 weeks. The faster production time means that you can utilize the same square metres for more production repetitions, which thereby creates a potential for an increase in sales.

"I was surprised that we were able to produce a shorter and more sellable plant with no use of PGRs only using LED grow lights," says Jesper Slot, former owner in the nursery where DGT by Senmatic carried out the studies and current CEO of Graff Young Plants.

"In addition to producing more young plants by square metre and from it increasing our sales, we were also able to accommodate the increasing interest and demand for young plants produced with no use of PGRs. Using only LED lighting, we had a product that could be promoted as free of pesticides with exception of control of fungal spores. Reducing use of chemical remedies is a supply chain liability and something the entire chain from propagation stations to procurement should seek to improve."

Jesper Slot CEO of Graff Young Plants

The added value factors should naturally also be included when calculating the collected cost of investing in changing from traditional HPS lighting to modern LED grow lights:

"You have to look beyond savings relating to electricity costs, when investing in LED. Our customers experience less loss, less retardation, and more uniform plants. Factors that all result in optimizing work procedures in the nursery. It is crucial to calculate the collected cost reduction."

Morten Hjorth Area Sales Manager at DGT by Senmatic

What we did

LED in replacement of chemical PGRs

The idea of using LED lighting in replacement of chemical PGRs began to grow in Jesper Slot after having been in contact with DGT by Senmatic, where he got wind of the convincing impact LED has on plant growth and growth regulation. In collaboration, a study on the effect on Osteospermum was carried out in the nursery, which Jesper Slot co-owned.

In a small test compartment of the nursery, which produced millions of Osteospermum to be sold throughout Europe, four varieties of Osteospermum were placed under LED grow lights in the plant’s 8th week from 05.00 to 21.00 at a temperature of 16 degrees Celsius. To compare growth results, all four varieties had reference plants, which were growth regulated traditionally by using PGRs.

During the study, different light combinations were tested. Research has shown that red light stimulates rooting, and thereby “stretches” the plant, while blue light “pulls” and thereby impacts the height of the plants.

- Use of grow lights in agriculture and horticulture has been thoroughly examined. Research has found that blue light results in compact growth, while red light impacts stretching. This might, however, vary based on culture – in some plants the exact opposite might be the case. For instance, it is just the opposite in tulips, tells Morten Krage, while Jesper Slot agrees:

- It is a well-known fact in the horticultural industry that the colours of LED can affect plant growth, but there are still some unanswered questions, and not all plants have been examined. That is why we decided to examine Osteospermum, which we produced for the European market.

With the Sunny Osteospermum variety Emma repeated tests of plants under different LED light combinations and referenceplants treated with PGRs under traditional HPS-lighting were carried out. The photo below shows the different between the reference plant treated with PGRs and HPS-lighting (to the left) and a plant regulated only by using LED-lighting (to the right).

Example of the study’s findings – Sunny Osteospermum Emma:

The tables below show the test results for the Sunny Osteospermum variety Emma. The three tables show how the light combinations have impacted the plant. Note that the only changes in growth regulations are the combinations of LED-lighting – controlling light combinations is easily managed using DGT by Senmatic’s LED controller or our climate control. The reference plants have all been treated with PGRs six times and have been placed under traditional HPS-lighting. It is worth noticing that even with a non-controllable, permanent LED light plan, remarkable results were experienced.

- It is thought-provoking that it is possible to completely remove chemical PGRs during formation just by using LEDs, says Jesper Slot.

In addition to studies on the Emma variety, similar studies have been carried out for the Sunny varieties Atilla, Galina, and Carlos.

Traditional growth regulation using HPS-lighting and PGRs LED growth regulation
Light composition Traditional HPS-lighting (and PGRs) Red LED 94 %, blue LED 6 %
Development Larger and brighter leaves Smaller and darker leaves
Branching No topping No topping
Compact No difference in the internodes No difference in the internodes
Height (average) 5.5 cm 4.5 cm
Traditional growth regulation using HPS-lighting and PGRs LED growth regulation
Light composition Traditional HPS-lighting (and PGRs) Red LED 86 %, blue LED 14 %
Development Less uniform and less value in the foliage More value in the foliage, very uniform
Branching No topping No topping
Compact Less compact More compact
Height (average) 5.5 cm 5.5 cm
Traditional growth regulation using HPS-lighting and PGRs LED growth regulation
Light composition Traditional HPS-lighting (and PGRs) Red LED 90 %, blue LED 10 %
Development Less uniform and less value in the plant Uniform and more value in the plant
Branching No topping No topping
Compact Longer internodes Shorter internodes
Height (average) 5.5 cm 5 cm

What is plant growth regulation?

Growth regulation changes plant cells and impacts the plant’s physical appearance. Through growth regulation, factors such as height, distance between internodes or how bushy the plant appears.

Why do we regulate plant growth?

Regulation of plants is done to create a more sellable plant to the stores’ procurement teams, and to end users, purchasing plants in the stores. To store buyers, it is particularly important that plants are compact rather than tall and instable. Smaller, compact plants make it possible to transport more plants at a time – transport, which most often occurs in standardized CC-containers.


Considering LEDs?

DGT by Senmatic’s LED top lights are available in several varieties, including light bars with lens systems. Our solutions are suitable for most modern commercial greenhouses and are designed to withstand the demanding environment in a greenhouse and maintain performance during its long lifetime. The minimalistic design means easy installation using standard connection technology, and with a minimal shadow footprint.

One of the major benefits of our LED fixtures is the ability to control the spectral distribution. Investing in a controllable LED fixture means that you always have the option to change the light to keep up with new research findings, a new culture/culture stage, or simply to dim the fixture when less light is required. Simply put, an investment in DGT by Senmatic LED grow lights will not leave you with a fixed spectrum but leads to endless possibilities.

Some of the highlighted benefits are:

  • Control of spectral composition and dynamic control of light intensity
  • Several variants, each with their own specific scope, such as vertical farming, commercial greenhouses, climate chambers, garden centers, production areas with special lighting requirements, hybrid installations, indoor environmental planting and "green walls" - and more.
  • Energy savings 
  • Long lifetime with no reduction of the light output over time
  • Consistent light on the plants due to a patented optical lens system


Have you become curious about the difference between traditional light and LED? Read our review of HPS vs. LED here

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Controllable LED fixtures

In this brochure you can find a comprehensive overview of our range of controllable LED fixtures.

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Any questions? Please contact our specialists

Johnny Rasmussen Johnny Rasmussen Business Development Manager +45 20 80 11 03
Morten Hjorth Morten Hjorth Area Sales Manager +45 20 80 11 16

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