For results from research with plants in controlled environments to be even partly transferable to plants growing in sunlight the light should be similar to sunlight. By similar we mean here both photon irradiance (the amount of light) and spectrum (the colour). This is very rarely achieved in the controlled environments routinely used. There is an additional dimension that is routinely ignored: the temporal variation in irradiance. It is still common in controlled environments to use a simple light/dark protocol while daylight irradiance really follows a bell shaped curve in the absence of clouds, and much more complex patterns under broken clouds or even more and faster variation within plant canopies.

Although a day/night square pattern in irradiance is used in much of current research, recent designs of growth chambers usually allow “ramping” of settings, i.e., gradual transitions between conditions, including light levels. The simulation of sunflecks or rapid pulses during plant growth is not possible with commercially available controlled environments.

So, what is special about this facility and its new light sources? 1) Irradiance can reach 1600 \(\mu mol m^{-2} s^{-1}\) or about 80 to 90% of that at solar noon on midsummer day under a clear sky in Helsinki. 2) The spectrum within the visible region is the nearest to sunlight achievable with current LED technology, i.e., a very close match. 3) The chamber controller allows ramping of all settings, so changes through the day in all controlled variables can be programmed if desired to be gradual. 4) The light sources support both constant and pulsed illumination.

The SenPEP and CanSEE research groups have available an assortment of light sources and optical filters that can be used to modify the spectrum by addition or subtraction of specific wavebands including UV-B, UV-A, VIS and NIR. This is crucial for photobiological experiments such as we do. This additional equipment is not part of the facility but available for collaborations.

The ability to manipulate the light conditions requires for its proper use instrumentation for measuring spectral irradiance, that is measurement of the amount of light of each wavelength so as to describe both amount and colour of light. The SenPEP and CanSEE research groups have spectrometers that can be used for this.

This facility, although small, is unique worldwide and targets research on the role of light in the ecophysiology of plants. That is research that investigates the role of light in plant responses in their natural, or for crops, production context. This facility is open to all staff of OEB. However, research that makes full use of its special features is prioritized. Capacity is limited with only three small chambers, frequently making replication of experiments in time a must.

The video below shows Vicia faba plants growing in one of the chambers.

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