Hi,

     While taking the fresh weight the leaf surface must not be wet  e.g.  dew. Place the basal cut surface at the bottom of the falcon tube. Care should be taken while taking the turgid weight. We have to remove the surface water with the help of filter paper lightly. This step should be performed quickly and sample weighed immediately. Also the tubes need not be fully filled with water.

Moreover the uptake of water will depend on the plant water status. If in the stressed condition then the turgid weight will be more. In well-watered condition, the difference between the fresh weight and turgid weight will be less.

AlreadyAlready saturated leaf not take up water.

chilling probably does not help. We floated sections on a petri dish with a thin layer of water and put these on dry towel after 20 min. Also keeping a control in darkness with full water or wrappping it in aluminium foil may give some clue for turgid weight at leats in dicots, Simonneau T, Habib R.1991. The use of tree root suckers to estimate root water potential.Plant, Cell and Environment14,585–591.

Thank you all,

As suggested I placed the leaf section with the basal cut at the bottom and fully filled the tube with water (no air bubbles) and apparently it worked.

Floating in a petri dish seems to not work for wheat, as the wax that covers the leaf makes it very hydrophobic. Floating appears to be the best solution in my case. 

Cheers,

Alberto 

Surfactants and EDTA may be then the way of keeping cut vessels open and to ease water adhesion in thin layer. The treatment should be reversible on a hourly scale. In practice you may saturate and dehydrate a cut section at least twice in a day.

In the rubber plants, It was found that after a quick removal surface water using tissue paper and floating the leaf discs in a petri dish also not given a good result. As per your suggestion  adding surfactants or EDTA  will give a good and reliable result

I used this method for rice leaves several times, but couldn't observe a such problem.  I made approximately 1cm2 leaf discs after taking fresh weight ant completely floated them on  20 ml  distilled water containing petri dishes and covered them with their lids. After 12 hrs turgid weight was taken. This was work nicely in all the times. 

For measuring relative water content (RWC), the method of Weatherly (1950) and its modification by Weatherly and Barrs (1962) was adopted, following the considerations given by El-Sharkawi and Salama (1973). Leaf discs were punched from the center of the leaf. They were weighed to estimate their fresh mass (FM), floated for 4 hours on distilled water and weighed again to estimate their turgid mass (TM). For dry mass (DM) determination, the discs were oven-dried at 80ºC till constant weight. Relative water content was calculated as:

RWC = [(FM – DM) / (TM – DM)] X 100

Determination of saturation water deficit:

Saturation water deficit (SWD) was calculated according to Weatherly and Barrs (1962) from the following equation:

SWD = 100 – RWC

The case of rubber plants is different from rice plants, as there is latex in the vein which coagulate and prevent the entry of water.  leaf discs are weighed for fresh weight, that period of time induces latex coagulation and blocking of the vein. Thus the turgid weight, what we get is not good.