Orchids roots growing away from light?

[naoki]

I think if you read papers by Dr. Yin-Tung Wan (Texas A&M researcher), they mention the direction of root growth and light (photo-tropism) in phalaenopsis. The mass Phal producers want to keep the roots into the pots. So they have shown that the light in the pots (translucent pots) promotes the root growth inside of the pots (instead of outside). This matches with my observation, too. For many others, the roots seems to sense the direction of moisture (hydro-tropism). This includes Cattleya and Paphiopedilum. In non-orchids, roots generally show strong hydrotropism and gravitropism (gravity sensing).

[bil]

I am observing that on my mounts, all the orchids show one type of movement. They emerge from the moss, then dive back in it. If photosynthesis were the aim, surely the tip would remain outside of the moss. When roots quit the moss and move of up a branch they do so for a whille, and then the greenn tip 'dies' the root flattens and grows no more. Presumably this is acting as a anchor.

[estación seca]

bll, I think this has to do with your low relative humidity.

At one time in my sunroom relative humidity was in the range 40%-60% with a lot of non-orchid plants and me throwing buckets of water on the floor several times per day.

All the emergent roots that arrived with new plants soon died where they left the medium. Plants that had been with me for a while never sent roots far out of the medium.

I got an evaporative cooler and began using it all the time. The air blowing on the orchids has a relative humidity of 60%-70%. Now my plants send new roots far out of the medium in all directions, and they remain healthy. Many of the mounts have begun sending roots out of the moss and for some distance along the branch.

[calvin_orchidL]

Originally Posted by naoki

I think if you read papers by Dr. Yin-Tung Wan (Texas A&M researcher), they mention the direction of root growth and light (photo-tropism) in phalaenopsis. The mass Phal producers want to keep the roots into the pots. So they have shown that the light in the pots (translucent pots) promotes the root growth inside of the pots (instead of outside). This matches with my observation, too. For many others, the roots seems to sense the direction of moisture (hydro-tropism). This includes Cattleya and Paphiopedilum. In non-orchids, roots generally show strong hydrotropism and gravitropism (gravity sensing).

Naoki - resurrecting an old thread, but do you have a source of the Yin-Tung Wang paper?