"www.gardeners-advice.com" wrote in message
oups.com...

Circulating Air is an often overlooked necessity for orchids. Because
most orchids take their nutrients directly from the air, they do best
when there is a steady, constant stream of air around them. A small fan
or an open window will provide enough air flow to keep them happy.
Thanks for reading


If I had to pick only one issue with this post it must be the one above.

Epiphytic orchids take up nutrition with their roots and they get it from
dissolved nutrients in water that is running passed their roots down tree
bark and washing off leaves, etc during rain. It is a rather weak solution
of nutrients in comparison to what terrestrial plant roots can draw from the
ground. However, their roots are adapted to an environment that is NOT
nutrient-free. Rain water filtering down from tree bark and leaf surfaces
is surprisingly rich in nutrients and minerals created by and from the biota
being supported on these surfaces. Epiphytic orchids just like a lot of air
around their roots because they are adapted to living above soil. The
spongy layer of root tissue around the central cortex of an epiphytic orchid
root is adapted to do more than just cling to stuff. It sucks in
water/nutrients like a sponge and draws it into the central cortex which
then transports it up (via transpiration pull made possible by two nifty
properties of water; adhesion and cohesion) into the leaf and stem tissue
and out the stomata in an unbroken molecular chain. For two extra points
can you tell me the name of this spongy outer root tissue of orchid
roots...or even what type of plant cell it is made of?

Circulating air is important not because the plants would starve if the air
stopped moving (cough, cough) but because air that is circulating improves
their transpiration, i.e. the ability to circulate water and nutrients to
all their cells; although transpiration is also a function of relative
humidity, evaporation and temperature. And even more important to good
orchid cultivation, moving air helps prevent fungus and bacterial spores
from settling on plant tissue long enough to grow into it.