What you can measure with your MultispeQ

Updated: March 27, 2018

For an updated list of the Parameters that the MultispeQ V1.0 can measure, including References, check out the What does the MultispeQ measure article in the Help Center.

PhotosynQ production line, located in the Plant Research Lab dungeon!

Production of the MultispeQ has begun in earnest!  We have all the parts (except the circuit boards which are coming next week) to build 250 beta MultispeQ devices, and we’ve got Geoff full time on production to make it happen.  The hardware version is locked, device calibrations are known, the software platform is stable and works in the lab and in the field,  and we have a suite of high quality methods for measuring plant and soil health.  It’s been a long journey, but we feel good that we’re finally ready to let go 🙂

I’d like to take this post to give more detail about just what the heck you’re going to be able to do with your MultispeQ device once you get it.  Next to each measurement you’ll see a comparable commercial device, though it’s important to note in some cases the MultispeQ is more accurate, and in some cases less accurate.  Combined, the commercial cost of devices which measure everything described below is 10s of thousands of dollars so we think we’re doing pretty good!


The machinery of photosynthesis! The red circled items are areas which can be measured in some way using the MultispeQ.

Light Levels

LiCOR PAR meter

Photosynthetically Active Radiation (PAR)

PAR is the range of wavelengths of light which are actually absorbed by plants to do photosynthesis.  This range is 400nm (purple) to 700nm (dark red).  Standard light meters are influenced by infra-red and UV, which are not used in photosynthesis.  We use PAR, combined with the other measurements below, the figure out the flow of energy via electrons and H+ ions which ultimately produce sugar and plant tissues.

Chlorophyll content

Minolta SPAD meter


Chlorophyll content in the leaf has been shown to relate to overall plant health, and NDVI (a similar measurement taken using reflectance instead of transmittance) is used commercially to determine the timing of nitrogen application in corn and other crops.  This measurement is very short (about 1/2 a second) and can be calibrated easily in a few seconds in the field.  SPAD measurement was initially popularized by Minolta and they continue to produce most of these types of handheld devices.

Efficiency of Photosynthesis

Pulse modulated chlorophyll fluorometer

Photosystem II and Photosystem I efficiency

Photosystem II (PSII) is where most the energy gets captured from the sun which is used by plant to make food.  Tracking it’s activity, efficiency, and regulation tells us a lot about the condition of the plant.  For example, PSII efficiency changes based on stresses (like drought or lack of nutrients) quite quickly – in fact it is possible to spot a under-watered plant using PSII efficiency before the change is noticeable by eye.  We can calculate PSII efficiency by measuring infra-red chlorophyll fluorescence under various conditions – here’s a cool infra-red filtered time-lapse showing fluorescing plants in a growth chamber!

Photosystem I (PSI) also captures energy from the sun, but it’s role is a bit more complex and not worth diving into here.  But, knowing both PSII and PSI together can tell us linear and cyclic electron flow (the flow rate of the very electrons which ultimately produce ATP and sugars)… that’s kind of like measuring the pulse of a human being.  The faster our pulse, the harder we’re working or more stressed we are.

There are lots more details about these measurements and the mechanisms linked below:

Determining the limitations of photosynthetic energy transduction (warning – very in depth but lots of good information!)
See page 1112 in this article “PSI Electron Flux” for a description of PSI measurement using 850nm

ATP production

Benchtop spectrometer

Proton Motive Force (PMF)

We are quite proud of this measurement, because we are the only handheld device that we know of capable of taking it!  The Proton Motive Force (PMF) is the energy produced by the flow of H+ ions out of the thylakoid membrane (see picture above).  What does that mean?  If we imagine that photosynthesis is like a hydro-electric dam then PMF is the energy produced by the water flowing through the turbines.   But for plants, instead of turbines producing electricity, it’s the ATP synthase producing ATP.  We can estimate PMF by measuring something called electrochromic shift (ECS).

This is a very new measurement so we don’t have a lot of clear applications in the field as of yet, but we hope the PhotosynQ community will help us find more!

Photosynthetic regulation

Non Photochemical Quenching (NPQ)

Plants spend a lot of time dissipating energy from the sun because too much light can damage plant tissue.  Chlorophyll fluorescence is one way to dissipate that energy (fancy term for this is photochemical quenching), but the plant can also turn excess light into heat.  This dissipation as heat is called non-photochemical quenching, or NPQ for short.  Normally, it takes about 10 minutes or more to accurately measure NPQ, but Dave and Stefi have been working on a new measurement called NPQt which cuts that time down to about 10 seconds… which means plant breeders, ag extension agents, and others can take this measurement in the field, in real time!

Combining photosynthesis measurements

One measurement to rule them all!

We’re working on combining PSI, PSII, and NPQ described above into a single measurement which takes 10 – 15 seconds to complete.  This is possible because these measurements all share similar components, like a saturating light, a measuring light, far red, etc.  In fact, combining them is potentially better than performing them separately because the measurements themselves disturb the plant – so the fewer times you flash lights at the plant, the more accurate your readings will be.  Expect to see a blog post detailing this measurement soon.

Soil biological activity

Soil biological activity by CO2 accumulation

Soil CO2 production

Soil health is hard to measure because there are so many different components – nitrogen, phosphorus, potassium (NPK), micro-nutrients, the presence or absence of toxic chemicals, and other factors.  So measuring overall biological activity in a soil can give us a general indication of the soil health by measuring the CO2 produced by micro-organisms in the soil.  The rate of this CO2 production tells us the amount of biological activity.  Here’s an graph of some recent measurements we took showing the CO2 production of swamp, forest, and grassland soils taken in the field – swamp was the most active (fastest increase in CO2), as expected.

Soil organic carbon (humus)

Permangenate oxidizable carbon
Organic carbon in the soil helps maintain pH, reduces leeching of nutrients, and increases water holding capacity.  It can be measured by using a potassium permangenate solution according to this protocol.  We have done initial successful testing but can’t wait to get more feedback from the community on this method!

Soil moisture and ion concentration

Soil EC meter and display

Electrical Conductivity (EC)

While the MultispeQ itself doesn’t have a conductivity meter attached, you can purchase a conductivity meter and hook it into the MultispeQSoil conductivity, i.e. passing an electrical current through the soil and measuring it’s resistance, is influenced by the presence of ions like nitrates, potassium, sodium, sulfate, and ammonia as well as the presence of water.  It’s a tricky measurement, because it’s influenced by soil type and moisture levels.  However, we’re particularly excited about this because if we can collect global soil EC data, and correlate it with soil type and weather information, we think we could eventually predict soil ion concentrations.


Other ideas

Polyphenol concentration in grapes, relates to taste for wine makingBrix (sugar concentration), relates to taste and readiness for picking

Anthocyanin content in leaves, a measure of stress

Pulse oxymetry, not plants, but hey why not

Seed mold, seed storability by measuring temperature, CO2, and relative humidity

We can’t wait to get these devices out into the field, and see what you guys come up with… expect more updates soon!

Chlorophyll content measurement for PhotosynQ

Hey folks – just wanted to give you a quickupdate. I’ve made several improvements to the Arduino code in the last few days so that it’ll be easier for users to create new protocols! We’ll have a few measurements before the start of the Beta. Often called SPAD, this measurement was first commercialized by Minolta and they remain a big seller of chlorophyll content measurement instruments, specifically the SPAD 502 meter (http://www.specmeters.com/nutrient-management/chlorophyll-meters/chlorophyll/spad502p/).

SPAD measurement

Chlorophyll content can be a proxy for N levels in plants, and therefore indicate when additional fertilization is required. Here’s a quick little paper which uses SPAD measurements on 2 crops to predict N application: http://www.hort.cornell.edu/uhi/research/articles/horttech12%284%29.pdf. This technique is particularly proven in corn and several other major commercial crops – so pretty darn useful!

How it works

The SPAD meter measures transmission of 2 wavelengths (650nm and 940nm) through the leaf. The 650nm correlates with the presence of chlorophyll, while the 940 measures the leaf thickness. The ratio of the two tells you roughly how much chlorophyll is in the leaf (measured in SPAD units). This is a relatively easy measurement because neither light sources need bandpass filters (a bandpass filters out light outside of a narrow spectral band, for example from 640 to 660, to provide a more pure light source).Other companies have developed other techniques, like opti-sciences, which are a bit better (they don’t require that you clamp on both sides, they don’t require that the leaf completely cover the light guide, can wider range of chlorophyll concentration, etc.). That technique compares 700nm with 730nm which also correlates to chlorophyll content – however, this technique requires bandpass filters which are expensive. Read more about it here: http://optisci.com/ccm300.htm.

So we’re going with the good old SPAD measurement because we can do it with out current device setup and, most of the time, it’s just as good as the newer method.

Help make PhotosynQ SPAD-tastic

We are looking for any beta testers interested in helping us correlate our SPAD measurements with Minolta (or other brand’s) SPAD readings. If you’re interested, please shoot me an email!