Leaf size change since move to GH

[AHAB]

Hey All,
I moved my plants from my (wife's) sunroom into the greenhouse in October '08.
The new leaves on my paphs are wider and seem thicker, but they are shorter than the older leaves.
They have good color, medium green.
The roof and sides of the GH are 55% opaque white (made by GE).
I don't have any shade cloth put up yet as the winter sun is not that strong down here in Central Florida.

The plants look healthy and seem to be growing at a decent rate.
But I am very curious as to why the leaf size change.
Any ideas?
Thanks,
AHAB

[Ray]

Interesting.

Leaf shape is related to a lot of things, but mostly light accumulation and heat dissipation, with a broader, shorter, and thicker leaf having less of a surface-to-volume ratio, so less dissipation. (Look at the leaves on a deciduous tree like an oak or maple - the upper leaves that are not shaded by any above them are more deeply forked or "spindly", while those less exposed to the sun lower down are broader and less sharply- or deeply forked.)

If your plants are needing less heat dissipation, I would speculate that it's a reaction to lower light levels, better air movement, or both.

[Brooke]

I have a slightly different thought on your shorter, thicker leaves since the move to the g/h.

I think the leaves are receiving more light and don't need the larger leaf surface to feed itself.

If you take two of the same plant and grow one in full sun and one in full shade, which will have the biggest leaves? The shade plant - the growth will have larger leaves, the overall growth will be lankier with fewer blooms.

The full sun plant will be much more compact, smaller leaves and more blooms.

I am finding orchids follow the same growth habits regarding more sun/less sun as my garden perennials display.

Brooke

[AHAB]

Hi Ray & Brooke,
Thank you for your thoughts!
I should have mentioned that these are seedlings that I got about one year ago.
After thinking about your responses, you brought to mind several
other thoughts:
They are now getting much more light over the course of the day than they did in the sunroom, but the light is diffused through the polycarb.

In the sunroom (covered roof) they were getting less total time of bright light, but more direct afternoon sunlight through the windows. The windows are double paned and are slightly tinted.
I do have a quite a bit of a breeze going in the GH.
I have two rotating fans and two box fans and the wet pad keeps the humidity at a minimum of 60 to 80% plus, in cold weather it gets very high.
It will be interesting to see how they develop in these new conditions over time.
Thanks again,
AHAB

[Ray]

Probably a combination of light and heat dissipation effects, then.

As a point of discussion, I didn't go the "light" way, as I assumed "shorter but wider" leaves would have approximately the same surface area as longer but narrower, but of course Brooke was right to bring up that possibility.