Emilia Jarochowska wrote in message ...
Hello,
I'm searching for any tip about the importance of photosynthetical
utilisation of water in the whole sucking force of leaves. Does oxygen
production contribute to the osmotic potential of xylem, and therefore
to water absorption in roots?
I don't need any quantitative information, a simple yes/no would satisfy
me as long as it's based on facts. I'll be very grateful for your help

Best regards,
e.

No, dissolved oxygen would not affect osmotic potential, which is a
component of water potential. Dissolved solids, such as potassium ions
or sugars such as sucrose do lower the osmotic potential. Water moves
in the xylem in response to the water potential gradient. Movement is
from higher to lower (more negative) water potential.

Most of the oxygen is going to exit the stomata, not dissolve in the
xylem anyway.

The main association of photosynthesis with water transport in the
xylem is that the opening of stomata, which is required for
photosynthesis, creates a huge water potential gradient from the leaf
intercellular spaces to the atmosphere. The leaf intercellular spaces
have virtually 100% relative humidity and zero water potential. The
atmosphere typically has a very negative water potential.

The following webpage has the equation to calculate water potential
from the relative humidity:

http://www.decagon.com/tru_psi/water...al%20info.html

David R. Hershey