Phal appearance with different light
 

In another thread, Izzie made an interesting observation:
"Some of my phals that used to have long leaves, now have shorter fatter leaves as I give them higher light"

I have always used leaf color to judge whether phals need more or less light.

I will start watching leaf shape also. Has anyone else observed this? Are there other differences you are noting with varied lighting?

The closer to light the lighter green the leaves get at least that's what I've noticed with the bunch I have. As far as leaf size and shape I really have never seen any big difference. I have some under lights, some in a North facing window, and some facing southeast. All are presently spiking and a few have flowered and this is under various lighting conditions. Happy growing.

If you re-read the thread, I mentioned my Bulbophyllums do go through noticeable leaf size and shape changes due to intensity of light.

These changes can be very drastic. Plasticity is the term that describes a plant's ability to physically adapt to its environment.

In my phals the change in leaf shape can be quite significant. Most of the year they are growing in a low light east facing window, and leaves produced then are quite wide. For most of the summer they moce to our summer house, where they sit in a south window with dappled shade. The light is much much stronger there, and leaves that grow then are up to 5cm narrower! However some plants show stronger differences that others. In high light the plants don't need as much surface area, so don't waste energy making wider leaves. Leaf length stays the same. Normally in a healthy, well fed plant new leaves should always be as long or longer than the previous leaf.

In stronger light the leaves tend to be a bit lighter colored, but the differences are not as striking as with leaf width.

Some interesting observations.

In oak and maple trees, the lower, more shaded leaves tend to be broader and less deeply cut, compared to the thinner, pointier ones up high exposed to the sun. That more-pointy shape allows for better heat dissipation.

It would seem to make sense that a plant grown under more intense light might need to dissipate heat more, so would tend to grow more elongated and thin.

But to throw another wrench into the works, I have often heard it said that flower structure tends to follow leaf structure, so it is recommended to buy phals with broader leaves, as the flower segments will be fuller and broader as well.

I pretty sure with my phals that some of them always grow long thin leaves and others always grow shorter and broader. But then they are all in about the same light. I've not tried varying the light on one orchid to see if it has an effect.

I HAVE noted that my Masdevallia's have much shorter broader leaves on the new ones they grown (both of my two Masdies) compared to their old leaves. I believe this is due to a change in light levels between the nursary and where I grown them but I don't know how the nursary grew them.

However when I first bought the first one I had it in LOWER light than now and it seemed to grow tall like the original leaves. I now have them both in higher light (outside in a green house with natural light, rather than on a windowledge with natural light) and the leaves are now growing shorter and fatter.

This seems to be the oposite of Ray's opservation on trees, BUT is the same way arround Izzie observed on Phals.

I wonder if rather than heat disipation it's a bit like the way some plants go 'leggy' when in the dark. They try and grow longer in the hope of reaching a brighter area, if they've got plenty where they are then they fatten in place instead :dunno:

Thanks all for the observations and thoughts.

Sounds like there are things to notice here that I for one hadn't paid attention to (had been focused mostly on leaf color and general plant health).

Quick survey today made me think that almost all of my phals seem to have much longer thinner leaves than I remember, except for the ones that have a reddish tint from high light. Unfortunately without measurements it just is an old guys memory, and .... what were we talking about?

It could be that the plants grown in brighter light are able to photosynthesize more efficiently and therefore don't need as much leaf surface as a plant grown in dim light. The plant grown in dim light with try to make up for the light deficiency by increasing leaf surface area and producing more cloroplasts hence the darker green color. My plant biology is a little rusty so I may be all wrong here. ;)