Other causes for purple Phalaenopsis leaves besides high light?

[whygreenberg]

Well, that title says it all, pretty much. You can see in the attached photo that this Phalaenopsis (Baldan's Kaleidoscope) is growing a new leaf. And that new leaf is mighty purple. I'm curious if there are things apart from high light which might be causing this coloration.

It looks to me like the result of strong light. But I'm curious and puzzled because I would not think this Phal's location would afford it that much light. (However, if it *were* getting that much light in its present location, I would be thrilled—it would open up a brand new, as yet unexploited growing area to add to. )

Your thoughts much appreciated!

[King_of_orchid_growing:)]

This may not be a scientific answer, and is definitely not the cause for it to be purple, but on many of the darker leaved Phal hybrids that pigmentation on new leaves does show up.

However, I can take a stab at making an educated guess as to why.

I'm assuming it's because it hasn't fully developed all of it's chloroplasts yet, so the pigmentation of the leaf shows up.

[camille1585]

First thing I would think of aside from light is that the plant makes dark colored blooms, but that's not the case of BK. I have noticed on my phals that young or emerging leaves are much more sensitive to light than the older leaves. The older leaves won't show any signs of purple at all. I have no idea if it's enough light to bloom them or not, since I moved my phals to a higher light zone shortly after noticing that.
What sort of light is that growing area getting?

[King_of_orchid_growing:)]

You know what...

I was just sitting around thinking about this question more and I thought about a documentary about plants I watched on YouTube.

It was talking about plants that were growing in the shade and how they were adapted to capture as much sunlight as possible while growing in shady spots in the forest.

According to the documentary, the purple pigmentation underneath the leaves acted as a reflective surface. When the little bit of sunlight enters the top of surface of the leaves the purple pigmentation doesn't allow the light to pass all the way through, thus trapping and reflecting the light onto the photosynthetic portion of the leaves.

I'm assuming that that's the reason why shade growing Paphs have those purple undersides to their leaves.

[whygreenberg]

That's some very interesting info, King!

Camille—This Phal doesn't fit in my growing area (because it is so huge! Backstory and photos here: http://www.orchidboard.com/community...eidoscope.html) So it is sitting on top of a bookshelf about a full 4 feet away from my growing area—which means 4 feet away from a 105watt CFL bulb, and a total of about 6 feet away from a south-facing window.

Not having a light-meter with which to measure FCs, I would absolutely assume that it's definitely too far from the light sources to cause that kind light-induced coloration.

[camille1585]

Seeing how quickly light levels drop off as you get further away from the light source, that is way too fare away from the light. So maybe the purple in this case is not light related at all.

[flowerpower]

I have rescued an orchid recently and it has a small leaf growing too. The underside is a bit purple but all the other leaves are green. Maybe it's a new leaf thing?

[LauraN]

Originally Posted by King_of_orchid_growing:)

You know what...

I was just sitting around thinking about this question more and I thought about a documentary about plants I watched on YouTube.

It was talking about plants that were growing in the shade and how they were adapted to capture as much sunlight as possible while growing in shady spots in the forest.

According to the documentary, the purple pigmentation underneath the leaves acted as a reflective surface. When the little bit of sunlight enters the top of surface of the leaves the purple pigmentation doesn't allow the light to pass all the way through, thus trapping and reflecting the light onto the photosynthetic portion of the leaves.

I'm assuming that that's the reason why shade growing Paphs have those purple undersides to their leaves.

How interesting is that!
Thanks for an exciting lesson on phals today!

[cb977]

:

[Ross]

Let's not forget genetics. Some Phals and Paphs have purple leaf coloring because they have purple leaf coloring. Strong light causes a different form of coloring and typically shows up as small dots (like coarse pixels) on a leaf surface facing the light source. Many (and I mean many) Paphs and Phals exhibit this coloring even when shade-grown (at least in my experience.) I tend to grow mine in strong light (2500 foot-candles or more) and I still see light green leaves, dark green leaves, purple edged leaves (like yours) and top leaf surfaces that are tinged red from high light. Sun can do it as can lights. But purple edges is not typically from high light (or any cultural cause that I know of) nor is purple coloring at the base of the plant and leaves.