How do Orchid roots actually work?

[King_of_orchid_growing:)]

Originally Posted by Fernando

But the question is still there: how do they actually work? Let me explain: where does the active/passive transport of nutrients an water happen?

The short answer is:

1. Diffusion.

2. Osmosis.

3. Capillary action.

Originally Posted by Fernando

If the velamen harvests water (including the dissolved nutrients), even for a short time until the entire liquids has been absorbed by the/into the vascular bundle, a overfeeding would be very likely to occur...

The velamen is inefficient with "harvesting water". It deflects a large amount of streaming water. It seems to only allow fine mists or a limited amount of small water droplets through.

It functions better as a form of water loss prevention for the cortical cells (i.e. cells in the cortex of the roots). This is one of the major functions of this thickened layer of epidermal cells.

The other function of velamen (or the function of any epidermal layer) is to protect soft tissues from physical damage. In this case, the soft tissues that the velamen is protecting is the root's cortex.

Originally Posted by Fernando

But if the velamen does not act a a sponge but acts as a barrier, than it would make sense to flush water regularly to clean substrate AND roots from excess of salts.

The velamen is spongy in texture, it doesn't necessarily act like a sponge.

Excess salts can build up on the roots as a result of the velamen acting primarily as a "barrier", rather than functioning as a highly efficient sponge. Like I said, it doesn't seem to allow certain things through in large quantities.