[APD] RE: Leaves and cuticles

["Thomas Barr" <tcbiii at earthlink_net>]

> Maybe. I don't know. I know it can utilise the CRASSULAcean Acid
Metabolism
> (CAM) photosynthetic pathway. That would make CO2 usage more efficient.

It'll concentrate CO2 around the Rubisco, CAM and C4 all use the similar
acids, they do not need the Kranz antomy to do this as is the case with the
best studied C4 plant, Hydrilla.

> > Another possibility is that it is getting CO2 underground; but I think
> > this is unlikely. A substrate high in CO2 would be strongly reducing &
> > this would not be a good habitat for a plant with limited oxygen
> > producing potential.
> The substrate can be just a few millimeters thick in nature, not much
chance
> for reducing conditions.

I think he means from respiration by bacteria in the soil. Lobelia
dortmatta(sp) gets most of it's CO2 this way but most plants would greatly
prefer high CO2 in the water in terms of growth.

> > How do we know how thick the epicuticular wax layer is? Are you judging
> > by appearance or analysis/measurement of the layer?

You need to do slides and measure this. This means a lot of work.
Most true aquatic plants do not have much cuticle. I've looked at many
slides of aquatic leaves. 

> But remember that the plant is a CAM user, and
> therefore efficient.

What plant?

> I think I read an article by Tom Barr somewhere re CAM
> photosynthesis in aquatic plants. Maybe Tom would like to elaborate...

Sure, See John Keeley's research, he's done a fair amount with CAM(Isoetes)
in aquatics and most work by my professor George Bowes with Hydrilla(C4
without stomata or Kranz anatomy, there are other C4 aquatics).

> And thinking about it, I wonder if Anubias has stomata on its submerged
> leaves? That might explain a few things. Tomorrow I will have a look under
> the scope...

Well, you can have a very thick cuticel on the adaxial side of a leaf and
then a very thin layer on the abaxial side.

Leaves are dramatically different on each side on almost all plants we grow.

Tom Barr

>
> regards
> Stephan
> Malta



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