1. Don't edit my posts.
2. since water can only hold 18mg/l O2, any readings higher than this are physically impossible." I don't believe this any more than the cow jumped over the moon, show me how you arrived at this DO concentration limitation,
http://www.ramp-alberta.org/river/water+sediment+quality/chemical/temperature+and+dissolved+oxygen.aspx
https://water.usgs.gov/software/DOTABLES/ (this is a good one)
http://www.water-research.net/index.php/dissovled-oxygen-in-water
there are literally HUNDREDS of government and educational websites that support my claim
3. "...optimal DO for plant growth, as long as you keep your DO in an acceptable range for the system that you are growing in your roots are excellent at repelling pathogens." You are correct, and what DO Sat do you consider an acceptable range that must be sustained continuously throughout the growing season?
It depends on what method you are using to grow. Using Kratky's non-recirculating method plants thrive from about 7ppm and up, commercial NFT requires about 40ppm, DWC is ideal above 9ppm. DO sat isn't commonly measured in aeroponic systems.
4. "Problems happen when DO dips too low, the roots get sick and can be attacked... You are correct, real big, serious problems. So what DO is too low in your opinion? And, by the way, just how do you accurately measure your DO?
Again, ideal DO sat is dependent on what growing method is used. With a fucking DO sensor like everyone else. You can also use colorimetric or titration. Winkler titration is the most accurate.
5. "OR if temps get too high (because temp has an inverse relationship with DO)." And we are back to the heart of the matter, DO -- insuring minimal safe elemental dissolved O2 continuously minute by minute for all the rhizomes and all the beneficial microbial colonies.
You actually meant "ensuring".
6. "So again, all we need are airstones, and maybe a water chiller." And your solution to insure minimal safe continuous O2 which is vital is airstones, [plenty air bubbles] and water chillers, right?
Yes, and proper circulation.
7. You are understating the importance of temperature in relation to dissolved oxygen as well." Yes the relationship is inverse. Lets not omit or discount the direct relationship O2 gas partial pressure has in the big picture, the greater the partial pressure of O2 in water, the greater the DO saturation that can be achieves - but greater than 105% DO Sat is unnecessary.
You actually mean how many atmospheres of pressure the solution you are working with is under. Which for everyone is a maximum of 14.7psi at sea level, and less at altitude. Partial pressure solubility is irrelevant in this application.
8. At the root level this oxygen starvation reduces the permeability of roots to water, and consequently the absorption of mineral salts, which will weaken the plant and eventually lead to a poor crop. Under continuing stress conditions, the roots will emit ethylene, a stress hormone that accumulates in the roots and participates to the slow degradation of the root system. Furthermore, ethylene is recognized by some pathogens as the sign for a weak individual, and a motivation to attack." Does this mean that insuring a constant supply of the element O2 is absolutely vital? If you are correct, and I believe you are, then what DO Saturation must be supplied 24/7 month after month throughout a growing season?
Well, I just don't really know how to respond to this. It seems like you are just asking rhetorical questions. Yes, plants require oxygen. I think everyone knows that. Again, the DO saturation depends on the growing method used. There are so many studies about this.
9. "Would you look at that, all we need are airstones and maybe a water chiller." I did and, the cow jumped over the moon.... hurrrrrrrrrr
durrrr
