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04-hydraulics.Rmd
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04-hydraulics.Rmd
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# Hydraulics
## Leaf turgor loss point, $\pi_{tlp}$
We assessed the leaf turgor loss point, $\pi_{tlp}$ in MPa, from a previously established relationship with the osmotic potential at full hydration, $\pi_{osm}$ in MPa. $\pi_{osm}$ is linked to the equilibrium solute concentration value $C_0$ (in mmol.kg^{-1}) directly measured with a vapor pressure osmometer (Vapro 5600, Wescor, Logan, UT). This is referred as the *osmometer method* (Bartlett et al. 2012a; Maréchaux et al. 2016).
### Materials
* Vapor pressure osmometer (Vapro 5520, Wescor, Logan, UT)
* Vapro software (Vapro Lab Report)
* Fridge
* Liquid Nitrogen
* Ziplock bag
* Paper towel
* Distilled water
* Metal tea ball
* Tin foil
* Needle
* Liquid nitrogen gloves + goggles
* Liquid nitrogen contenant
* 2 Tweezers
* Cork borer
### Methods
#### Installing Vapro for measurements
* Turn on Vapro the day before for the thermocouple's stability
* Test Water Quality [*cf Vapro_cheatsheet*](document/machine/Vapro 5520)
* Clean
* Calibration [*cf Vapro_cheatsheet*](document/machine/Vapro 5520)
* Control tests [*cf Vapro_cheatsheet*](document/machine/Vapro 5520)
* Verify temperature
* Always have the black diamond at the center of the display
Used daily:
* clean beforehand
* select automatic mode (10 runs)
#### Sampling on the field
* Collect at least 3 healthy mature leaves on branch
* Place them in sample ziplock bag with:
+ wet paper towel
+ Exhale in bag to saturate in CO~2~
+ Annotate bag with sample information
* Zip bag and stock in cooler
#### Lab measurements
##### Field day
* Recut branch under water
* Replace in ziplock bag with wet paper towel
* Put 24h in fridge to hydrate overnight
##### N+1 Field day
Vapro:
* check distilled water in vapro reservoir
* clean
* select automatic mode (10 runs)
* make sure vapro software is on
Sample measurement:
* Sample from a leaf a 5 mm disc with a cork borer: *avoid 1^st^ and 2^nd^ order veins to avoid apoplastic dilution that would lead to less negative osmometer values*
* Wrap disc in tin foil
* Immerse in liquid nitrogen for at least 2 min using metal tea ball
* Puncture 10-15 times with needle
* Place in vapro chamber
In total, disc are exposed to air for less than 40 seconds for all the steps.
* Record value C~0~ when the difference between consecutive 2-min measurements fell below strictly 5 mmol.kg^-1^ after at least three runs.
* If error! or Nr_Run > 10 :
+ try a 2^nd^ cycle with same leaf
+ try a 3^rd^ cycle with another leaf
+ otherwise record *NA*
* Beware of the stuck leaf inside the vapro! If so [*cf Vapro_cheatsheet*](document/machine/Vapro 5520)
##### End measurements
Clean Vapro
For more information on the vapro machine, please refer to the [*cf Vapro_cheatsheet*](document/machine/Vapro 5520).
## Leaf midday water potential
### Pressure chamber method
### Psychrometry method
## Relative water content RWC (%)
### Material
*Ziplock bag
*Paper towel
*Distilled water
*Fridge
*Analytical balance
*Sharpie
*cooler
*envelop
### Method
Before going on the field:
* write individual code on ziplock bag
* preweight ziplock bag
On the field:
* collect leaf
* clean leaf with clean paper towel
* place leaf in preweighted corresponding ziplock bag
* place bag in cooler for transport to the lab
In the lab:
* weight the closed ziplock with the leaf (*fresh weight*)
* delicately take the leaf out of the bag, wrap it in moist paper towel and place the wrap back in the ziplock bag
* place ziplock bag in the fridge during 24 hours
* 24 hours later, take out the leaf and wipe off water excess
* weight re-hydrated leaf (*saturated weight*)
* place leaf in envelop for oven-drying during at least 72h
* weight dry leaf (*dry weight*)
Calculate RWC (%):
RWC = $\frac{(fresh\ weight-dry\ weight)}{(saturated\ weight-dry\ weight)}$ X 100
From Sapes et al 2020 and Barrs & Weatherley 1962.
## gmin
## gs