On Jun 7, 6:17 am, "Ray B" wrote:
An interesting question, Bob.

I see something similar, and I grow in a greenhouse, so the humidity is
usually quite good. I have always chalked it up to individuals, rather than
type of plant, but maybe I just didn't catch the connection.

The velamen is supposed to capture water, and I had never heard of the
"prevent moisture loss" concept applied to it.

Might it have something to do with age, or maybe what the conditions were
like when the roots grew? The concept there is that maybe - if the plant
was watered well during the time of the growth of those specific roots - the
velamen was not a crucial part of the uptake mechanism, so didn't develop to
absorb as readily as that that grew under drier conditions.
--

Ray Barkalow - First Rays Orchids -www.firstrays.com
Plants, Supplies. Books, Artwork, and lots of Free Info!

Hi Ray!
I don't know if it's due to age or not. I've always noticed the way
my plants roots responded to the application of water, but never
questioned it before. I'm going to try and pay closer attention for
the next few weeks to see how the various roots on each plant
responds.
I did notice last night, watering the Den biggibum, that the oldest
part of the root darkened rather quickly. And the closer to the
growing tip, the whiter the velamen. I'm going to see if that holds
true for the other plants as well.
Another interesting thing I noticed is the growing tip of the root on
the Christieara is reddish ... I believe most, if not all the other
plant's root tips are green.
Bob