Inside is Out and the Outside is In...

[rbarata]

I think it is more likely that curled leaves reflect not enough water while the leaf grew.

Exactly! They curl to avoid losing precious water.

[jkofferdahl]

Originally Posted by rbarata

I was curious to see what would be an explanation but I have a theory based in my experience with a phal that was under too much light in summer. A new leaf curled as it was growing to minimize, I think, the area exposed to light.
I've out it further away from the window and have turned it to force to get a more natural position (it was curled and bent) and slowly if has uncurled and nos has a more natural look.
It doesn't seems to be harmful because it's growing a spike.




I believe it's just a defense mechanism...it happens also when plants are under too much heat. They curl probably to prevent excessive water loss by transpiration, also acting as a refreshing mechanism due to water accumulation in the confined space created by the curling.

Just a theory...

I'm going to agree with ES. Underwatering during leaf growth is, I think, far more likely.

[rbarata]

Well, two points of view of the same thing.
Lack of water due to underwatering and/or high evapotranspiration due to too much heat/light.

[jkofferdahl]

Originally Posted by rbarata

Well, two points of view of the same thing.
Lack of water due to underwatering and/or high evapotranspiration due to too much heat/light.

If the problem was too much light then I'd expect the leaves to either have a bit more of a yellow hue to them or else show signs of light damage. I see neither in these photos.

[rbarata]

If the problem was too much light then I'd expect the leaves to either have a bit more of a yellow hue to them or else show signs of light damage. I see neither in these photos.

Agree! When I mentioned too much light I was thinking in terms of heat. In rooms with lots of indirect light temps and HR are usually higher.

[jkofferdahl]

Originally Posted by rbarata

Agree! When I mentioned too much light I was thinking in terms of heat. In rooms with lots of indirect light temps and HR are usually higher.

Too much heat would reduce RH and cause the plant to dry out more quickly, so we're both on the same track.

Every time this thread pops up, it sticks an old Beatles' song in my head. "Everybody's got something to hide except for me and my monkey." When my daughters were young - the older was in middle school so over 15 years ago - we made a trip to a place called Build-A-Bear, where kids select an animal, have it stuffed, select outfits for it, etc. The older daughter made a monkey, dressed it in "moddish" clothing, and named it Paul.

[rbarata]

Ops, now I've noticed my mistake...with higher temps HR is lower (not necessarily but almost always).

Basically what I'm trying to say is that leaf curl is a defense mechanism against water loss, be it caused by too much heat/light/low humidity/ underwatering, whatever.