Wax layer destruction from seed coats

Question

I'm working with some orchid species, and i encounter a specific issue. Some of those species deposits upon their seed coat a wax layer. This layer makes seeds behave in a very hydrophobic way. You cannot dispense them in a pour water.

That behavior has many impacts. One of the most significant is that it does not let water come in touch with the actual seed and then with embryo to make it sprout.

So i tried many ways to remove that layer but nothing actually seemed to work out.

I treated seeds with the following chemicals:

a) 1% NaOCl with some dish soap water solution for 10min. After throwing seeds into this solution you could see that they can be evenly dispensed in it and come in touch with the solution. But if you wash them up with pure water for example 3 times they are getting back their hydrophobic behavior.

b) 1% H₂SO₄ water solution for 10min. I thought that with this treatment waxes will be removed from the seeds but nothing like that happened. Maybe they had been better dispensed in the pure water comparing to the previous treatment but nothing significantly changed.

c) 93% ethanol solution for 1, 2, 3, ... 30min. results here were also very disappointed. While the seeds are immersed into ethanol, they were very well dispensed into the liquid without any hydrophobic behavior. After three washes with pure water, hydrophobic properties came back.

Treatment time seems not to play any significant role on the results.

My conclusion is that there is no destruction of the waxes with the above chemicals. The only thing that happened probably, is the creation of a Micelle around the seed, which make it for a while (the time that it was in the solutions with soap and ethanol) non hydrophobic.

Finally my question is, if there is any way to destruct chemically, to some grade the waxes. So even when you put the seeds in a pour water not be so much hydrophobic.

Thank you.

Answer 1

This paper describes dewaxing of sunflower seeds using various solvents. As you have already shown for yourself, using hydrophilic substances such as bleach and acids do not work well in removing the waxes.

Waxes are highly hydrophobic substances, and must be removed with either hydrophobic solvents (much like washing away acids with water at the emergency eye-shower) or detergents and water. The hydrophobic solvent mixtures used for lipid extractions recommended in WYSIWYG's link will likely work as well.

Answer 2

Try a nonionic detergent like NP-40, it is a very good surfactant.

Answer 3

Waxes look something like this:

• ref: http://lipidlibrary.aocs.org/Primer/content.cfm?ItemNumber=39369

So you will never be able to dissolve them with a polar solvent like ethanol or water. You need a detergent or an apolar solvent.

If I were you I would try out gasoline to dissolve the wax and soap + water after that to remove the gasoline remnants from the surface of the seed. They are cheap, but they might damage the seeds. If gasoline would be too strong for the seeds, you can use plant oils, like sunflower oil as apolar solvent too, but you might need to rub the surface with that, because it is very slow otherwise.

Using hexane and ethanol like in the article March Ho linked is somewhat more sophisticated, but chemicals are harder to procure at least in some countries.