Stem Turgor Pressure

Definition

Stem turgor pressure is the hydrostatic pressure inside living stem cells, expressed in kilopascals (kPa), that keeps tissue rigid and drives cell expansion. At GreenWorld Sector-7 it is measured continuously by PhytoSense Mesh magnetic leaf/stem-patch probes whose output is inverted (patch pressure rises as turgor falls) and calibrated to an absolute kPa scale per cultivar. It is the highest-cadence physiological channel in the facility at one sample per minute, giving near-real-time visibility of hydraulic state.

Why it matters

Turgor responds within minutes to changes in transpiration and root-zone supply, making it the facility's primary live hydraulic alarm and the channel CHLORA polls to time irrigation pulses. Its diurnal amplitude is itself diagnostic: a flattening day/night swing precedes visible wilting by hours. Turgor contributes 0.20 weight to the Canopy Vitality Index (VC-MET-001).

Formula

P_turgor = P_cal − k · P_patch

where:
  P_patch = magnetic patch-probe output (clamp pressure)
  k       = cultivar gauge factor (probe vs. pressure-bomb)
  P_cal   = per-probe zero offset (full-turgor reference)

note: patch output rises as turgor FALLS — the metric is the
inverted, calibrated value so higher kPa = more turgid.

calibration:
  cross-checked against pressure-chamber Ψ on tagged leaves
  weekly; gauge factor k re-fit monthly.

processing:
  1-min raw → 5-min median for CVI sub-index
  diurnal amplitude tracked as a derived health flag.

Reported to 1 kPa.

Inputs

Units & Scale

kPa, reported to 1 kPa. Strongly diurnal — highest at predawn, lowest midday — so thresholds are referenced to the cultivar's expected diurnal envelope, not a flat line. 1-min raw is reduced to a 5-min median for the CVI sub-index. Facility value is biomass-weighted. Confidence degrades if the probe gauge factor is overdue for monthly re-fit or if diurnal amplitude collapses below 20 kPa (suspected probe detachment).

Sampling & Source

• Sampled every 1 minute by PhytoSense Mesh patch probes — the highest-cadence channel.
• Reduced to a 5-min median before entering the CVI recompute.
• Diurnal amplitude tracked as an independent early-decline flag.
• Stale handling: flagged STALE after 5 min; amplitude collapse flags probe-detach fault.

Thresholds

Recent Trend

Facility biomass-weighted turgor, last 14 five-minute medians:

Interpretation Guidance

Related Metrics

Related SOPs

• SOP Library — patch-probe placement & monthly gauge-factor re-fit.
• Turgor WARN/CRIT triage & probe-detach discrimination — Operations SOP set in the SOP Library.
• Irrigation-pulse linkage & alarm escalation — Monitoring Systems.