Updated: March 27, 2018
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!
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 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
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:
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!
|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 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
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 MultispeQ. Soil 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.
|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!