DIMLUX PLANT TEMPERATURE CAMERA

A LOOK IN THE RIGHT DIRECTION

Dimlux introduced the first indoor plant temperature camera in 2011. At a time when concepts such as VPD (Vapor Pressure Deficit) and plant temperature were still unknown, this was an absolute novelty. Now that these concepts are slowly penetrating the market, it is time to delve deeper into the matter.

VPD has now become a bit of a buzzword, but the most essential information is often still missing, making the customer think that everything is in order, when is in fact working with completely wrong information. That ‘essential information’ is the plant temperature!

VPD AND PLANT TEMPERATURE

Using an online calculator to calculate the VPD without factoring in the plant temperature is incorrect. So incorrect in fact that those values will probably do more harm than good to the plants. With LED, due to the larger temperature difference between the air and the plant temperature, calculating the VPD without including the plant temperature is an absolute no-go! The VPD value from a calculation without the plant temperature is totally unreliable and may cause huge problems.

GROWING PLANT TEMPERATURE AND LED

When growing with LED, the plant temperature is more important than ever, because the grower often thinks in terms of the cultivation method and schedules of HPS, and applies them to LED. This often results in poor growth due to the sub-optimal plant temperature. Growing at air temperature is a no-go when growing with LED. This was in fact already the case when growing with HPS, but with LED the importance has only increased.

The reason that the plant temperature is so important when growing with LED is because the LED fixtures do not emit infrared radiation like the vast majority of HPS fixtures. The infrared radiation in HPS cultivation ensures a considerable increase in plant temperature, and an ‘ideal’ air temperature has been attached to this over the years. This is actually wrong. The plant temperature should always be leading and the air temperature indirectly controls the plant temperature.

If cultivation with LED is done at the same air temperature as with HPS, the plant temperature will usually be too low and therefore the RuBisCo enzyme cannot work properly. The RuBisCo enzyme is less active and limits CO2 assimilation.

The plant temperature also depends on the spectrum of the LED lighting, the intensity, and the VPD. For example, green light will heat up the plant more than other colors. It is therefore not possible to indicate an ideal air temperature. A base value can be used and then adjusted based on the plant temperature until the ideal plant temperature is attained.

HOW SHOULD THE PLANT TEMPERATURE BE MEASURED?

The plant temperature should be measured over an as large a leaf surface as possible so that a good average temperature is measured.

The parts of the plant that need to be measured are the parts that receive the most light from the assimilation lighting. Mounting the plant temperature camera at the same angle as the assimilation lighting results in the most accurate measurements. After all, photosynthesis takes place where the most light is absorbed.

With the Dimlux Xtreme LED with high penetration lens, the camera should be aimed such that it ‘sees’ the most foliage and the least amount of other stuff like soil. The sensor of the camera has a viewing angle of 50° which equates to, for example, a captured area of 1m in diameter at a distance of 1m.

WHAT IS THE DIFFERENCE BETWEEN A PLANT TEMPERATURE CAMERA AND AN INFRARED TEMPERATURE METER.

As opposed to an infrared temperature meter, the plant temperature camera is made to measure the temperature with a wide field of view, and with an emissivity matched to that of plants. This ensures the most accurate measurement possible.

An infrared temperature meter is made to measure the temperature of the smallest possible spot diameter. This way, only the temperature of a single leaf can be measured, and not of a complete plant, or several plants. When measuring from a distance, measurements can also accidentally be taken from the lower leaf layers where less or no light reaches. The emissivity parameter of this type of meter is adjusted to building materials, and not to that of plants. For an accurate measurement, the result must be converted.

The plant temperature camera also monitors continuously and does not just provide a snapshot.

HOW DOES THE PLANT TEMPERATURE CAMERA WORK WITH DIMLUX EQUIPMENT?

The plant temperature camera is available in 2 versions, analog and digital. The digital model is for use in combination with the LED Xtreme series and the analog model for use with the Maxi Controller.

When used with the LED Xtreme series, the ideal plant temperature will be shown in the display. In addition, if the plant temperature is too low, the auxiliary lighting will flash blue, and if it’s too high, it will flash red. The grower will then be able to adjust the air temperature or VPD to achieve the ideal plant temperature.

The plant temperature does not only measure whether the plant is in its optimal range for photosynthesis, it’s also an indicator of whether the CO2 level is too high because of closed stomata. When the CO2 value is too high or the VPD is too high, the stomata may close, and the plant temperature will rise as a result. With the optical message of the plant temperature camera, the grower is informed of the situation. In the event of a water shortage, the plant temperature will also rise.

When the plant temperature camera is used in combination with the Maxi Controller, it works fully automatically as a preventive measure. If the plant temperature is too high, CO2 supply will be stopped and the output of the fixtures will be gradually dimmed. This dimming continues until the plant temperature is back within its ideal range. If the plant temperature continues to rise, the Maxi Controller will switch off the lighting, because evaporation no longer occurs and the plant will only wilt. The lights will now stay off until the error is corrected.