Gas exchange through drainage holes

[Grim Tuesday]

Like some others I have found that I like to set my SH pots in saucers to catch "dribbles" from imperfectly drilled holes. But I ran out of saucers today, and I have an oversupply of slightly strangely shaped plastic Ikea pots (see picture; the SH pot is sitting on the lip of the lower pot). But the construction of the pots is such that it leaves very little clearance for the drainage holes, maybe about 1mm and probably interfering with any gas exchange that might take place through the drainage holes (I have another variety of this pot that makes a tight seal against the holes) What is the general thoughts about blocking these holes? Are the drainage holes important for gas exchange? Or is the air that goes up and down the top of the pot sufficient?

[isurus79]

I suspect 99.99999% of the gas exchange occurs at the surface of the media. I doubt the Ikea pot would have any noticeable effect on the plant.

[Ray]

^ What he said ^

[estación seca]

I'm not as certain as the above. It is surprising how much and how rapidly water will evaporate through a very tiny hole, so I suspect there is considerable gas exchange through the drilled holes. Ray and others have shown plants do well in S/H with no drainage holes, with water exchange by a siphon. So I don't know whether gas exchange through lower drain holes is important.

In one of my chemistry classes the instructor had us put the same amount of water in two identical trays, cover one tightly with metal foil, and had us poke a few holes in the foil with a toothpick - less than 10. At room temperature the water evaporated from the two pans at the same rate.

[Georg Luiz Barth]

Originally Posted by Grim Tuesday

Like some others I have found that I like to set my SH pots in saucers to catch "dribbles" from imperfectly drilled holes. But I ran out of saucers today, and I have an oversupply of slightly strangely shaped plastic Ikea pots (see picture; the SH pot is sitting on the lip of the lower pot). But the construction of the pots is such that it leaves very little clearance for the drainage holes, maybe about 1mm and probably interfering with any gas exchange that might take place through the drainage holes (I have another variety of this pot that makes a tight seal against the holes) What is the general thoughts about blocking these holes? Are the drainage holes important for gas exchange? Or is the air that goes up and down the top of the pot sufficient?

This is exactly my current setup... transparent s/h pot with side drainage hole placed inside a beautiful cachepot. I have not had problems with the internal roots, respecting of course the care inherent to the semi hydroponic culture.