Mechanisms causing root death

[Ray]

Originally Posted by K-Sci

How do you know the probiotic worked?

And for that matter, what the heck is a probiotic, and how to they work to stop infections?
-Keith

The infection stopped spreading and did no further damage.

Probiotics are beneficial microbes added as part of your feeding and watering regimen. Some predate pathogens, some exude antibiotics, others exude auxins, etc. Each species has its own secretions that have a positive effect on the plant, just like the micro flora and micro fauna that live inside us, aiding in digestion. Some are nitrogen-fixing and some are photosynthetic, meaning that they secrete food and fuel right I side the plant, without the plant consuming it’s own resources to do so.

[niamul21]

Originally Posted by K-Sci

If orchid roots rotted because infections set in when roots remain wet too long, neither growing in sphagnum nor semi-hydroponics should be viable growing options. Obviously the mechanism causing death from over watering requires something more than prolonged exposure to moisture. Some of the candidate modes of action sometimes theorized include:

1. Suffocation when sodden potting media blocks oxygen availability.
2. Suffocation when aerobic organisms consume the available oxygen when breaking down media.
3. Extremely low local pH caused by carbonic and organic acids produced resulting from decay.
4. Hydrogen sulfide produced by decay occurring in the absence of oxygen.

The growing techniques orchid growers use to prevent root death from over watering address these in two ways.

• They eliminate or reduce the organisms of decay that could deplete oxygen, produce acids, or release hydrogen sulfide. Examples include potting in scoria, Stalite slate, charcoal, Styrofoam, sphagnum, or LECA.
• They assure high oxygen levels throughout the root zone. Common techniques include growing on mounts, in baskets, and the use of sphagnum and LECA.

Semi hydroponics and growing in sphagnum are special cases because they appear in both the preceding lists. Sphagnum resists decay and contains many tiny air spaces that assure oxygen availability to roots. This is true so long as the moss isn’t so saturated that the spaces are filled with water. The LECA used in semi hydroponics does not decay and is porous to oxygen.

K-Sci

I do agree with the concept that you have covered up.

[K-Sci]

Originally Posted by niamul21

I do agree with the concept that you have covered up.

What is the concept I have covered up?
-Keith

[Dusty Ol' Man]

Originally Posted by K-Sci

What is the concept I have covered up?
-Keith

I think he meant 'covered' , not 'covered up'.