Reza:

This link provides you with tips:

https://books.google.co.in/books?id=47tmDAAAQBAJ&pg=PA216&lpg=PA216&dq=Does+boiling+water+removes+pollen+grains?&source=bl&ots=RXGvBjY4fz&sig=tx6jXmUxuZmAvN0f8l0gZD03N_g&hl=en&sa=X&ved=0ahUKEwjhg5f9qt_RAhWILY8KHZ4cDFoQ6AEIJTAC#v=onepage&q=Does%20boiling%20water%20removes%20pollen%20grains%3F&f=false

Best

Syed

it is better to sieve the water you are going to use., to make sure it does not contain pollen.

Best wishes

Suzanne

Dear Reza, I think that the question you are asking is if using boiling water during a step in one of your processes will destroy the pollen in your sample, right? It shouldn't. Pollen is a polymer and pretty resistant to lower temperatures. You can burn pollen, and scorch it in some cases. For example, I have worked with samples of volcanic ash from the eruption of Mt St. Helens in 1980...we had large amounts of hemlock pollen that was blown off of Mt St Helens during the eruption and off the slopes of mountain ridges north of the mountain as well. Many of the grains were scorched, but those temperatures were very high. If you have put boiling water into a plastic squirt bottle you know that it will get very hot and in some cases sag. The same happens with pollen. But it survives boiling water. I have also analyzed pollen from hot springs where the water was very hot as well. So if you take a core from a hot spring, you will find that the pollen is preserved as well. Sorry I haven't been around, but I tried to come in November, but the time was too short to get a visa. But my paper was read at the conference in Tabriz. Now with Trump the Chump in Washington, I will have to come as a tourist to visit Persepolis for the third time. (wink) Check my ResearchGate website for the paper that was given for me at Tabriz. Khoda hafez, Peter  By the way, despite what Mr "T" said on Wednesday, we are still trying to get students into the U.S.

The gametophyte ,according to my experience, dies in temperatures higher than 40ªC. If you have any doubt, carry on the viability test following to Alexandres technique or the viability test following to Greissle (this last one show you if grains are alive with capacity to germinate or not. Of course, the exine never is destroyed.

Dear Reza, you are speaking about fossil pollen, correct?

Khoda hafez,

Peter

Thank you all for your answers. I thought my question was not clear enough, so I edited it and made it more clear.

In fact I am asking about the possibility of contamination fossil pollen samples (FPS) with possible modern pollen grains within the distilled water which is used to prepare the samples. We use distilled water to wash FPS but the distilled water might not be barren of pollen and could add some modern pollen grains to the FPS.

As Suzanne suggested one alternative to make sure that distilled water does not contain pollen is to sieve the distilled water with 7 (or 10) micron filter (but unfortunately it takes a long time to sieve enough water for preparing large numbers of FPS).

I think since the specific weight of pollen is more than water then if we allow distiller instrument to provide some distilled water and give enough time to possible pollen grains to settle in the bottom of the bucket  then we can pure upper part of the distiller water into another bucket and use it to prepare FPS. I think It could decrease the contamination possibility.

Reza, You could also centrifuge the distilled water, if you have large enough centrifuge tubes. The pollen would settle and you can use the decanted water. 

Given your uncertainty about the water purity, I think the settling and or centrifugation method is best for large quantities of water. At that level of purity, you should also question the purity of air reaching your working area. One problem with fume hoods is that they pull all air towards your work space. Therefore, the entire room must be pollen free and the ventilation system filtered

Reza, the important point about the fume hood is the air velocity. If it is fast enough, pollen a silt-sized particle will not settle, but continue through and out of the air exhaust system of the fume hood. The chart below suggests that if your fume hood velocity is about 35 cm per second...any modern pollen in your lab should keep moving and not settle into your samples.

Did you tested to adding fluorhidric acid under an extractor until all the not organic parts are eliminated and soon after sieve the solucion with an adequate mesh ( 100 microns or less) under conditions of isolation and sterilizacion of the mesh and the test tube in a laboratory isolated from air flow?

I am not sure that this will destroy the pollen. This step would also be dangerous, and expensive. A centrifuge would be so much easier.

Dear Reza,

add a high quantity of recent exotic pollen and/or for instance Lyopodium spores to the water and see if you really find some of them after the distillation process in the distilled water.