In SPAC Analytics, parameters are divided by sensor.
The "Weight" and "Weather" sensors are given in any system, and any additional sensors will appear below them.
Parameters could be daily - one measurement per day, continuous - measurement every three minutes, or experimental – one value per experiment. All calculated parameters are based on the raw measurements of the sensors.
Below are the formulas and descriptions of the key weight-based parameters.
Continuous parameters
Weight [g]
Raw measurement of the system weight after basic corrections.
Allows a basic visual impression of the raw data and the course of the experiment.
Transpiration Rate [g/min]
Whole plant water loss rate. Calculated as the time derivative of "Weight".
Allows for inspecting and comparing the diurnal pattern of transpiration of each plant.
E [gwater/min/gplant]
Transpiration rate normalized by the plant weight*.
*User choice - Plant net Weight or Calculated Plant Weight.
E = Transpiration Rate/Plant weight
GS canopy per weight (Watchdog) [gwater/min/gplant]
Canopy Stomatal Conductance. Transpiration rate normalized by the plant weight (E) and divided by VPD measured by the Watchdog weather station.
Allows for inspecting and comparing the diurnal pattern of the canopy stomatal conductance of each plant.
Gsc per weight = E*Patm/VPD
GS canopy (Watchdog) [g/min]
Canopy Conductance. Transpiration rate divided by VPD measured by the Watchdog weather station.
Gsc = Transpiration Rate *Patm/VPD
Calculated VWC [cm^3/cm^3]
The Volumetric Water Content of the medium measured using Weight data only. The calculation is based on the mass balance difference of each unit.
*The parameter uses the values: 'Reserve Water inventory', 'Soil Wet Weight', 'Soil Dry Weight', 'Soil Volume' and the 1st-day weight as a reference point for each plant
*The parameter cannot distinguish soil-plant water loss.
Daily parameters
RDT Morning [g]
Reference Daily Transpiration morning. Average Weight in the morning.
*Morning time is defined by the user (RDT Start – Time).
*Averaging time is defined by the user (RDT Start – Duration).
RDT Evening [g]
Reference Daily Transpiration evening. Average Weight in the evening.
*Evening time is defined by the user (RDT end – Time).
*Averaging time is defined by the user (RDT end – Duration).
Daily Transpiration [g]
Daily water loss of the plant between morning and evening, as defined by the user.
Calculated as: RDT Morning(n)- RDT Evening(n), n(day)
Plant Growth [g]
The difference in plant weight between consecutive days.
Calculated as: Plant Weight reference time* (n+1) - Plant Weight reference time (n), n(day)
* Plant Weight reference time is defined by the user (Daily Weight Start).
Plant net Weight [g]
A daily calculation of the net weight of the plant by subtracting all the fixed pre-experiment measurements.
Calculated as: Plant Weight reference time (n) – (Tare Weight + Soil Wet Weight + Reserve Water + seedling Bulk Soil Weight), n(day)
Calculated Plant Weight [g]
The plant weight calculated based on the WUE value of each plant.
Calculated Plant Weight is derived from the plant's initial weight (weight at day 1) and accumulated by WUE*Daily transpiration.
This parameter estimates the biomass of the plant, based on its transpiration levels, and can be used in times when the pot water capacity is not refilled (like drought stress) and "Plant net weight" is not possible to calculate.
Experimental parameters
*Presented and edited in the "Experiment settings" page.
Water Use Efficiency (WUE) [unitless]
The ratio of the biomass gain of the plant to the water lost by the plant through transpiration.
WUE = Accumulate (Plant Growth) / Accumulate (Daily transpiration). Linear regression from start to end.
WUE value is the linear regression slope from the start to the end of the accumulation time.
Accumulation time is defined by the user (WUE start, WUE end). Times should be selected from the pre-treatment period, where plant growth is positive and daily transpiration is increasing.
Stress degree [unitless]
The normalized ratio of Daily transpiration at "Stress end" to Daily transpiration at "Stress start"*. Indicates the level of stress a plant has experienced based on changes in transpiration levels.
*"Stress start" and "Stress end" dates are automatically identified by the system based on changes in transpiration levels, and can be edited manually by the user.
Resilience rate [g/day]
The Derivative of Daily transpiration from "Stress end" to the next approximate value of "Stress start" (later than "Stress end" date).
Indicates how fast a plant recovers from stress based on transpiration levels.
Mass gain rate [g/day]
Rate of plant weight gain (Plant growth) between WUE start and end dates.
Indicates the rate of biomass gain of each plant at the WUE time period.