Just a quick 2¢ about the slime on the prop root tips. There's been a lot of talk recently about its function for feeding N fixing bacteria, and I think that is very interesting. I do not believe that is its only function though, and it isn't even an important function at the stage andi shows in the picture. When the prop root is up in the air like that and is dropping towards the soil, it doesn't have any feeder roots on it to absorb fixed N, even if there was some being produced. The purpose of the slime is to lubricate the root tip so it can break through the soil surface. If you look at those tips when they are slimy, it is a clear slippery gel/mucus. Later in the day it dries up and then is either reconstituted or the tip produces more overnight. Its clearly a hydroscopic mucus gel of some kind. If you think about what a prop root has too do, the plant is basically trying to stab a pencil into the soil in slow motion. It makes sense that the root tip would produce a compound to facilitate this. I'm sure once the root is below the surface, the bacteria feeding fuction begins to become important, but not above ground.
Hi Oxbow, agree totally the primary function of the slime/goop is to lubricate roots in the soil and likely feed soil bacteria/fungi. It's absolutely likely to be a secondary function thats evolved in the teosinte corn and over expressed in the Sierra Mixe varieties (and possibly others). Just that it's interesting to see it. But it does make you wonder, particularly in the composite Indian corns whether that trait is present even if it's not over expressed as in the Sierra Mixe corns. As far as I am aware from the recent paper no feeder roots are necessary to absorb the fixed N, that happens directly through the prop root and the continual production of the goop is to feed the N fixing bacteria.
I’ve seen it in multiple varieties of corn (mostly commercial). But what you need is extra moisture including enough humidity, and prop roots. If the prop roots get dry at some point in there life the will harden off and sometimes reabsorb. I think I would search Peruvian Germplasm as I have heard from people on this board that it has a lot of prop roots.