Has anyone benchmarked the METER SC-1 versus the LI-600 for stomatal conductance on Rosa hybrida under high-VPD greenhouse conditions? I’m mid-way through a 6-week trial at 22°C/60% RH and need reliable abaxial readings on glossy leaflets; ideally the unit exports clean CSV and holds calibration against an LI-6800 reference?
On glossy rose leaflets, my LI-600 stays within about 5–8 mmol m^-2 s^-1 of an LI-6800 if I use the small gasket, do a quick “zero before each block,” and shade the head so the leaf doesn’t warm, otherwise it’s like sealing on a Teflon pan. SC-1 can work but I had to re-zero every 15–20 min and press lighter to avoid microleaks, and the LI-600’s CSVs are cleaner; happy to share the paired-clip template I used for abaxial checks, @Anika.
Quick tip: at about 1 kPa VPD the SC‑1’s longer settle can drift; I’ve matched an LI‑6800 closer by backing each leaflet with a thin foam pad to flatten curvature and swapping to the stiff sealing insert — cuts abaxial leaks without goop. CSV-wise, the LI‑600 gives clean USB.csv while the SC‑1 needs METER’s downloader and its timestamps can lag; @jameson_p23’s shading note is solid — if you see ‘creep’ after 3–4 s, abort and re‑clamp; want a tiny QA template?
I’ve had better luck on glossy abaxial surfaces by pre‑shading the leaflet for about 90 seconds, then clamping so the head equilibrates with your ‘22°C/60% RH’; that kept readings within about 5 mmol m^-2 s^-1 of our reference across a 6‑week block. Small caveat: if you export CSV from the SC‑1, set the device language to English or you’ll get comma decimals — are you seeing drift mainly in the first few seconds or throughout a block?
And i get tighter agreement by feeding the handheld a true leaf temp with a tiny thermocouple and rejecting any clamp where the leaf–head delta-T is >0.5°C — like giving it a quick reality check. To curb drift over the trial, do a two-point RH check in a zip bag (silica gel zero, MgCl2 about 33% span); good refresher here: https://www.metergroup.com/environment/articles/porometer-best-practices/. Are you logging leaf temp separately or relying on the chamber reading?
One thing that helped me with glossy abaxials was a quick “blank clamp” at your “22°C/60% RH” on a strip of PE film to confirm near‑zero; if it’s not, a tiny gasket nick or a slightly skewed clamp was usually the culprit, and fixing that pulled my handheld in line with the bench system. Do you see any pre‑ vs post‑block drift over the 6‑week run?
I’ve had the LI‑600 track an LI‑6800 within about 0.02–0.05 mol m⁻² s⁻¹ on Rosa when I stop gasket skate on glossy “abaxial” leaflets by laying a thin matte silicone dental‑dam strip with a 6–8 mm punched aperture between leaf and head so only the spot is exposed — think of it as giving the gasket traction. Caveat: under high VPD it drifts if the fan screen or gasket gets dusty, so I do a weekly zero/span with the check plate and clean the screen; LI‑600 CSVs are tidy, but the SC‑1 tends to settle slower — are you seeing longer stabilize times on the SC‑1?