I’ll outline the method that we use for pollen processing and storage. This isn’t the only method out there, this is just the one we’ve be using for years.
I made a comment about using once blooming roses as pollen parents, and I believe that Kim and Dave asked me how we stored the pollen. So, here you go guys!
First, I collect unopened flowers. Yes, this means I collect the bud stage (making sure the reproductive organs are not visible).
Take them back to the lab. Remove the petals, just as we would if we were going to pollinate it. Once reproductive parts are exposed, remove anthers. We place them in paper boats for a few days. (Just make sure anthers are dry so they will release their pollen!)
Place dried anthers/pollen in a small tube. Technically, they’re ‘microcentrifuge tubes’. I like them because they are small, transparent and have a screw cap. When I started working in the mid 90s, we were using 35 mm film canisters. I don’t like them so much because the top was a simple snap on/off sort of a thing and I never felt like it did a good job of keeping the pollen contained (but that’s just my opinion…).
[attachment 482 Pollenintube.jpg]
Once pollen is placed in the tube, it’s placed in a small clear box with a layer of desiccant in the bottom. We use Drierite, which is Calcium Sulfate (anhydrous).
This box is now ready to go to the freezer. Pollen for the ‘active year’ is stored in the freezer part of a refrigerator (which is generally around -20?C). Older pollen gets stored in an upright freezer that does not have ‘frost free’ feature. Why? Because in order to be frost free, the unit will increase the temperature to just above freezing for a brief period in order to allow any condensation to melt and drain away, and then re-freeze. I just feel that the temperature cycling is not good for long term storage (but once again, that’s just my own opinion).
[attachment 483 Freezer2.jpg]
I usually collect several vials of the same pollen and keep one ‘active’ and the others in storage. Sometimes, accidents happen and the pollen you needed/wanted goes missing or just get dumped out…but I’m sure none of you have ever had that happen!!
When we are not using the pollen it is stored in the freezer. When we use it, I move the box to the refrigerator for ~1 hour. Then, I get a small cooler and put a few ice packs inside and place the pollen box (with the desiccant) in the cold cooler and head to the greenhouse.
Pollen vials are only removed from the cooler when we are actively using them. They are replaced once we are done with that particular pollen and then we grab the next pollen and repeat the cycle. Once we are finished pollinating for the day, the pollen goes back to the freezer until the next day.
We never have any problem with condensation building up on the inside of the tubes. Yes, there can be a little that forms on the outside, when in use, but a quick wipe gets rid of it.