>> In particular, the purpose of leaves is to absorb as much sunlight as
>> possible. Given that task, you would /expect/ leaves to evolve to be
>> huge flat sheets.
>
> Huge flat sheets would mean that only the outher layers get sunlight.
> Inner branches might just as well commit suicide immediately.

Huge flat sheets are not a good design for several reasons:

1) Which orientation would you align these huge leaves towards?  Or you 
mean to arrange them like a balloon covering all directions with a 
hollow inside?  In both cases your tree is going to be a huge sail and 
get uprooted very easily in strong winds.

2) They would need to be much thicker (and heavier) than lots of smaller 
leaves in order to keep their shape, and thus the branches supporting 
them would need to be much thicker (and heavier).  As warp already 
mentioned, other trees would then be able to get higher with more 
efficient designs (thinner branches and more smaller leaves) and at 
least partially block your sunlight.

3) Leaves fail all the time, they get eaten, blown off, snapped off etc. 
  If you've only got a few large sheets then there isn't much redundancy 
in the system, your tree will likely die if just 1 or 2 leaves get broken.

4) With lots of small leaves it is easy for the tree to adjust to 
maximise the sunlight, it can let a few leaves die that are in shade and 
grow news ones to take advantage of extra light very quickly.  With a 
small number of huge leaves that is not so easy.

Post a reply to this message