How those leaves float?
 

Can anybody help me find books or papers to read? For free-floating
and floated-leaf plants, I know air is trapped and density is lower
than water. People told me:" upper leaf surface is hydrophobic and
unwettable (so it floats); and lower surface is hydrophilic". Is that
true? I want to find books or papers to verifiy this. Thanks a lot.
Z

How those leaves float?
 

In article . com,
wrote:

The upper surface of floating leaves is clearly hydrophobic because of
the waxy cuticle. However, it does not seem logical that a hydrophobic
upper surface is required for the leaf to float. Rather, a hydrophobic
upper surface, due to the waxy cuticle, would be required to prevent
desiccation of the leaf.

Some floating plants also have hairs that trap air. Both traits help
the plant turn upright and rise to the surface if disturbed.

I'd recommend the original poster examine leaves of these minimalist
floating plants (e.g. duckweeds, azolla) and observe whether and how they
trap air when they are submerged. Plant nurseries that sell water garden
plants, and some of the better tropical fish stores may have a selection
of various species. Both flowering plants and ferns can have this form.

Z wrote:
Can anybody help me find books or papers to read? For free-floating
and floated-leaf plants, I know air is trapped and density is lower
than water. People told me:" upper leaf surface is hydrophobic and
unwettable (so it floats); and lower surface is hydrophilic". Is that
true? I want to find books or papers to verifiy this. Thanks a lot.

As David pointed out, many floating plants have aerenchyma, tissues
that are full of air and very low density, so they act as floats.
Examine a water hyacinth -- you'll see spherical swellings at the
base of the leaves, which float the plant which has its leaf blades
entirely in the air. The entire leaf is water repellent.