On Jun 7, 4:31 pm, "Diana Kulaga"
wrote:
Good topic for discussion. I find that among groups of our plants the degree
of "greenness" varies. Some of the Phals, notably the ones with thinner
roots, green up immediately. But we have some that have much thicker roots,
and in order to get them green it takes a good deal more water. I have made
the assumption (yes, I know, that's dangerous) that the dark green roots
cannot absorb much more. So far, the growth rates in both types are similar.

Bob, with regard to your biggibum, the roots on our superbums green only at
the tips. The same goes for reed stem Epis. And the variation in "greening"
in our Vandaceous plants is enormous.

We grow outside under screen.

Diana
Hi Diana,
So apparently this greening isn't due to the low relative humidity in
my house. You're in Florida, I believe and Ray has a greenhouse, and
you both have noticed the same thing. As does Kye.
My general assumption was that velamen, functioning to absorb water,
would be very quick to grab it as available. And the green color was
due to the chlorophyll in the roots becoming visible. I guessed my
relatively dry atmosphere caused the velamen to thicken (maybe), and
the root would become green quickly to maximize water intake. Even
perhaps going so far as to perhaps develop a one way mechanism - quick
on the uptake, slow to evaporate. As opposed to a high RH situation
where the velamen didn't have to work so hard. There being plenty of
moisture in the air. ( I kind of expected that in a high RH situation
orchid roots would be green most or all of the time. There would be
no real change of color).
When I started to pay attention, however, I didn't see the quick
greening of roots like I expected. At least not on every exposed
root. Encyclia tampensis is another one in that the greening is so
faint that unless I look closely, it appears white. And that has lots
of exposed roots. The bigibbum that I thought stayed white really has
some very faint green after watering.
Well got to go ... my daughter needs the computer for school.
Have a great day!
Bob Campoli