Leaf collapse? Why??

[Stone]

A true epiphyte in Borneo and Philippines where air humidity rarely drops below 80% and it rains almost every day.

If we were talking about epiphytic Cattleya maxima I'd say no problem with the sparse humidity and watering regime.

Yes but if it doesn't rain for a couple of months - which can happen - roots will dry ( not desicate of course ) and all epiphytes have evolved to cope with this. but I agree it is generally a ''wet'' area. I was refering mainly to dryness at the root. I let my lowii almost dry out before I soak it and it seems to be doing well however I do spray the leaves almost every day.

 

[Rick]

Yes but if it doesn't rain for a couple of months - which can happen - roots will dry ( not desicate of course ) and all epiphytes have evolved to cope with this. but I agree it is generally a ''wet'' area. I was refering mainly to dryness at the root. I let my lowii almost dry out before I soak it and it seems to be doing well however I do spray the leaves almost every day.

Epiphytes have evolved to cope with very different conditions for different forests/climates.

All slippers are C3 plants while just about all Catts are CAM. That alone will tell you that the amount of water needed for any slipper (whether at the roots or in the air) is going to be quite a bit more (and continuous) than for a Catt.

I haven't seen any data on Mexipedium so maybe that will be the first CAM slipper discovered. But Paph parishii (also an epiphytic paph from the same subgenera as lowii, but with thicker leaves) was tested for C3/CAM capability and it came out C3 even though it probably comes from even dryer regime than lowii.

Compared to a CAM plant, C3 plants are water hogs with pores open at day regardless of temp and humidity.

 

[Stone]

Epiphytes have evolved to cope with very different conditions for different forests/climates.

All slippers are C3 plants while just about all Catts are CAM. That alone will tell you that the amount of water needed for any slipper (whether at the roots or in the air) is going to be quite a bit more (and continuous) than for a Catt.

I haven't seen any data on Mexipedium so maybe that will be the first CAM slipper discovered. But Paph parishii (also an epiphytic paph from the same subgenera as lowii, but with thicker leaves) was tested for C3/CAM capability and it came out C3 even though it probably comes from even dryer regime than lowii.

Compared to a CAM plant, C3 plants are water hogs with pores open at day regardless of temp and humidity.

Yeah its not quite that simple. Phals are CAM and they grow in the same sort of humidity your talking about. Also CAM and C3 orchids were found growing on the same tree in Nth Queensland.

 

[ALToronto]

My affected phals are now growing new leaves, and the new ones are flawless. At the same time, the temperature in my home, at the window, has gone up from nighttime lows of 16 degrees to 20-21. Could it really be a temperature thing?. The poor phals are exceptionally ugly right now, but one is in bloom, and 4 others just finished blooming.

What I find most interesting is that mature phals were affected much more than the 100 or so phal seedlings sitting right beside them. Of the seedlings, only 5 plants were affected. The seedlings were deflasked last July, and managed to grow through our brutal winter.

 

[Rick]

My affected phals are now growing new leaves, and the new ones are flawless. At the same time, the temperature in my home, at the window, has gone up from nighttime lows of 16 degrees to 20-21. Could it really be a temperature thing?.

Could be, and add humidity.

My night lows during winter are also around 16 C. But this year which is worse than the last 10, in that the day high in my GH may only have got up to 18C on cloudy days.

Overall that has to be a winter stress for stuff that normally stays above 21C.

I think you are under lights, what is your day length set too?

 

[Rick]

Yeah its not quite that simple. Phals are CAM and they grow in the same sort of humidity your talking about. Also CAM and C3 orchids were found growing on the same tree in Nth Queensland.

I also read recently that a Phal species was (I think amabilis or aphrodite) was determined to have CAM leaves and C3 roots. And even within CAM there are degrees of it.

Certainly quite a bit of complication, but just on a metabolic basis, C3 consumes a lot more water than CAM.

 

[Stone]

Certainly quite a bit of complication, but just on a metabolic basis, C3 consumes a lot more water than CAM

Agreed

 

[Happypaphy7]

The mystery continues.

I thought I have seen some pits on my paphs, but wow~ that looks quite serious! lol

I have asked people about this collapse, and basically no one knew what causes this.

I am dying to know for mainly curiousity's sake because almost all my paphs (over hundred) have varying degree of this kind of cell collapse and they all seem to do well.
Some do not have any at all or very few in the shape of very very tiny hole, while some have quite a population of them in certain area on the leaves.
Then some have indentation that are much bigger, but all of them are confined to a small area of a leaf as opposed to the picture of the original thread starter.

I see this occur both on old and new leaves.

I do not think it is water or temperature related.
My paphs are well watered, and these still occur.
I have been gone up to two weeks with no one coming in to water and I do not see sudden increase in numbers when I return.

I have very moderate temperature all year around in my apartment.

I think it could be those mites that are invisible? but no idea.

Apparently, the plants grow and flower fine.
So far, it's mainly just aesthetic, but I would love to know what it is and why it is happening.