Hi Y'all!

I have a question. Are mycorrhizal fungi needed by orchids in order to grow?

The reason I ask has to do with de-flasking seedlings. If we provide simple sugars for orchid seeds/seedlings during germination and the flasking phase of their lives, then when do they stop needing this "pre-digested" food? At what point are orchid seedlings capable of functioning independantly of this need, and able to digest their own complex carbohydrates?

I know that we deflask seedlings at an arbitrary point based on their morphology (size, roots, etc.), but does this mean that they are capable of functioning without our help? And if not, does this contribute to seedling mortality, and to what degree?

I recently changed my pre-potting soak for seedlings, and began adding sucrose to the mixture. I don't know what effect this will have, but I am interested in hearing your thoughts and opinions.

Brian
I will be interested to follow this thread to see the discussion evolve. Remembering the chemistry and biology I learned a long time ago, the plant produces its own simple sugars by photosynthesis. What is not consumed for energy is stored as more complex carbohydrates (cellulose). We provide the sugars in flasking medium for the protocorms as they develop roots and start to produce leaves and start to produce food for themselves.

The extra sugar in the deflasking soak may benefit the fungi and bacteria in the planting mix and they, in turn, will break down the complex materials into more readily available ones for the orchids. Much like the "boost" provided by garderers who the coke or other sugared beverages as a soil additive or spray. gets the soil bacteria going and the plants benefit. So maybe the deflasked seedlings don't need the sugar directly.

IMHO?
John

You raise an interesting question. My impression is that the mycorrhizal fungi function is for germination of the seed in the wild, and that the agar achieves this purpose in the flask. I have not seen any problem with deflasked seedlings searching for the symbiotic relationship with such fungi. Of course many crosses in the old days were sowed directly at the base of the mother plant, probably for the express purpose of using such a relationship to germinate. One observation is that such plants seem to develop much quicker than antiseptically produced seedlings.

I would guess that adding sugars to the mix would be of little effect other than attracting insects and breaking down the mix quicker.

I agree with Bill.

Orchid seeds are extremely immature, and are barely more than an embryo encased in a membrane. They need the micorrhyzal fungi to act as a root system in the seed's early stages of development. Once the seedling has roots of its own it repays the fungus by helping to feed it, hence the symbiosis.

Adding sugar to the solution will only coat the seedlings in fungus food and increase the likelihood of problems.

Interesting point, Bill about the seedlings produced au naturalle being stronger. I suspect this is because only the very strongest will survive the prototcorm stage. Also they will not suffer any setback due to deflasking.

Bill and Paul have very valid points. It's also unclear how readily table sugar can be utilized by the plant, as the product of photosynthesis is glucose, and table sugar (sucrose) is a disaccharide composed of one glucose and one fructose.

Obviously, the plants can survive in flask without any mycorhizzae at all. In fact, I suspect that if you could grow the plants in completely sterile conditions in a big enough of a flask with a replenishable supply of nutrients, the plants could grow to flowering. (Ive read that phals can actually flower in flask!)

You might consider adding glucose (aka dextrose) into your watering solution. While the microbes may digest most of it, a useful quantity may make it into the plant and help with growth. If you have enough seedlings, you could take half and treat with a sugar water regimen and the other half without the sugar water regimen, and compare the effects over time.

Interesting thread...:cool:

Bill and Paul have very valid points. It's also unclear how readily table sugar can be utilized by the plant, as the product of photosynthesis is glucose, and table sugar (sucrose) is a disaccharide composed of one glucose and one fructose.

Obviously, the plants can survive in flask without any mycorhizzae at all. In fact, I suspect that if you could grow the plants in completely sterile conditions in a big enough of a flask with a replenishable supply of nutrients, the plants could grow to flowering. (Ive read that phals can actually flower in flask!)

You might consider adding glucose (aka dextrose) into your watering solution. While the microbes may digest most of it, a useful quantity may make it into the plant and help with growth. If you have enough seedlings, you could take half and treat with a sugar water regimen and the other half without the sugar water regimen, and compare the effects over time.

Dean,

Don't paphs in the wild need the mycorhizzae to penetrate the seed coat (which I understand in paphs is especially tough relative to other orchids) and germinate? I understood that modern mediums add an enzyme (in various forms) that accomplishes the same thing. So, while paphs may not need mycorhizzae to "grow", don't they need it (in the wild at least) to germinate? :unsure:

Don't paphs in the wild need the mycorhizzae to penetrate the seed coat... and germinate? I understood that modern mediums add an enzyme... that accomplishes the same thing. So, while paphs may not need mycorhizzae to "grow", don't they need it (in the wild at least) to germinate?

In the wild, most/all orchids need some sort of mycorhizal association to get going, and some to continue to grow for the rest of their lives (cf Corallorhiza).

The destruction of the seed coat is required on some level for nutrients & fungus to enter the seed, definitely. In nature, the most prominent example would be the hardy orchids where multiple freeze-thaw's disrupt the coat. I suppose bacteria and physical erosion might produce similar results in tropical species... Maybe even the digestive juices of various herbivores...any evidence here?

In sterile culture, this abraision occurs in the "sterilization" phase of the seed. H202 is strong enough to abraid seeds and destroys the coat in most tropical species. For hardy orchids with that nice thick coat, like Cypripedium, sometimes up to 6 hours in a 10% Bleach solution is required to get good germination. "Sterilization" of Cyp seed is better called "scarification", because the actual sterilizing part only takes 10 minutes.

Best,
Ross

Hi Cajun Lawyer Dave,

I just noticed this older thread, and discovered that you had addressed a question to me. Well, better late than never...

Paph seeds are very fine compared to other orchid genera. I would expect that like most seeds, the seed coat is composed mostly of cellulose.

While I am aware of enzymes that break down cellulose, I am not aware of any that are added to flasking media for use in paphs, and I've talked with a number of folks who are professional flaskers or very serious hobbyists. I've not heard of enzymes being added to the media, and actually, I think that is quite unlikely for the following reason:

The media (containing agar) is autoclaved (heated under high pressure just like in a pressure cooker, or in the case of hobbyists, IN a kitchen pressure cooker). The vast majority of enzymes will completely denature (i.e., fall apart) and become inactive at those temperatures/pressures and that length of time. After all, autoclaving is a simple, cheap means of sterilization, and causes massive denaturation of nearly all the enzymes inside the microbes you are trying to kill.

But if you can point me to a reference describing a procedure for using an enzyme in media, I'd be quite interested to learn more...

Regards,

DYH

There is no protocol that uses enzymes to improve flask results, from what I understand. There IS a protocol that uses gibberellic acid to improve germination. It works very well in terrestrials, from what I've been told, and I actually have a published study, if you are interested. The heat problem is resolved by adding the hormone AFTER autoclaving via microfiltration.

I guess I'll jump in here too. The seed 'coat' or testa poses problems with infiltration of the disinfectant to the embryo. Scarification can help with this, but there are other ways to achieve it (vacuum, ultrasonic). Is the scarification to allow the embryo to enlarge and 'pop' the testa as it germinates, or is it to allow disinfectant/nutrient media to penetrate from the outside in?

As for the myco-question, I'd say no. In culture, there is no need for mycorrhizae. In nature, there is only a need at early stages as discussed. In culture, we can provide exactly what the orchid needs, so I'd say no.

Hi Cajun Lawyer Dave,

I just noticed this older thread, and discovered that you had addressed a question to me. Well, better late than never...

Paph seeds are very fine compared to other orchid genera. I would expect that like most seeds, the seed coat is composed mostly of cellulose.

While I am aware of enzymes that break down cellulose, I am not aware of any that are added to flasking media for use in paphs, and I've talked with a number of folks who are professional flaskers or very serious hobbyists. I've not heard of enzymes being added to the media, and actually, I think that is quite unlikely for the following reason:

The media (containing agar) is autoclaved (heated under high pressure just like in a pressure cooker, or in the case of hobbyists, IN a kitchen pressure cooker). The vast majority of enzymes will completely denature (i.e., fall apart) and become inactive at those temperatures/pressures and that length of time. After all, autoclaving is a simple, cheap means of sterilization, and causes massive denaturation of nearly all the enzymes inside the microbes you are trying to kill.

But if you can point me to a reference describing a procedure for using an enzyme in media, I'd be quite interested to learn more...

Regards,

DYH

Hey Dean!

I was told some years ago by a doctor who was a member of our local orchid society that things like bannana or papaya are sometimes used as additives not only for the sugars but the enzymes to aid in germination. He's also the one who told me that paph seeds needed something added to the media to penetrate the seed coat. It seemed plausible at the time since I had already flasked Brassavola nodosa and those seeds germinated and grew like weeds.

I have only used commercially prepared media myself in the past (and yes, the good old pressure cooker got the sterilization job done for me!). My home brew flasking case was not the most beautiful piece of art, but got the job done. I remade a cross of Paph. Sally Berendt and got one of the seedlings awarded and HCC/AOS. Since then I only buy flasks/compots from growers like you who have the right equipment and more knowledge than me. :p But, you just know that I had to try it myself at least once!! ;)

Thanks for the info on the enzymes. I may not be doing my own flasking anymore, but this stuff interests the hell out of me!

Thanks!