Laelia roots growing away from the light

[SaraJean]

Sorry, nothing helpful to add but your sarcs are beautiful!

[isurus79]

Originally Posted by estación seca

I know of one Sarcochilus breeder here in the US, Fred Clarke of Sunset Valley Orchids. I've shied away from Sarcs since I have warm to hot conditions in summer, and Fred describes them as intermediate growing.

You're in one of the cooler parts of Australia. How hot do your Sarcs get in summer? Do your summer nights cool down significantly?

I got a complex hybrid from Fred and it did just fine outside in Texas all summer!

[SaraJean]

Originally Posted by isurus79

I got a complex hybrid from Fred and it did just fine outside in Texas all summer!

Well that’s good to hear. I was curious how they would do for me since I don’t have a cool down at night in the summer. I picked up my first one early last spring and put it s/h, which set it back, but it’s growing and adapting well. The growth was definitely slow but I don’t know if that was due to heat or the media change. I just got two more in the fall and I’m going to keep those in bark and clay pots and see how they handle my climate. Just going to add a fan to my grow area and see if that helps with the heat as well

[Greenhousedreams]

+1 on what bil said. With phototropism auxin is broken down by light on the side of the stem that has the most exposure, which causes the opposite side of the stem (containing a higher concentration of auxin) to elongate faster than the side that is exposed to light. This causes the stem to bend towards the light.

Auxins promote growth in the shoots and slow growth in the roots so it is the same mechanism but an opposite result in the roots.

Also plant root caps are directed by gravitropism which relies on special organelles that settle to the bottom of the root cells. That accumulates auxin at the gravitational bottom of the root cap and causes elongation of the root downwards to the center of the earth.

So it seems that your Laelia is using a combination of negative phototropism and gravitropism to grow down and away from the light, where its roots would likely desiccate faster.

[Dollythehun]

I think I learned that (and forgot it) from Botany class! Thanks, great reminder!

[bil]

Good point on the tendency to grow downwards, but what I notice is that in the roots, negative phototropism trumps the effects of gravity. Where the light is the same all round, roots will grow downwards, but if there is something dark nearby, the roots will grow towards it even if it means they grow upwards.