DCMU problems

P.Ralph at uts.edu.au P.Ralph at uts.edu.au
Thu Sep 14 23:06:21 EST 1995


Dear Netters,

I've been trying for several months to run a series of DCMU treated stress
trials with the seagrass Halophila ovalis.  Unfortunately, everything I do
causes a permanent and significant decline in the Fv/Fm ratio after DCMU
treatment before being exposed to the stress.

I've tried vacuum infiltration, treatment in the dark, treatment in the
light and ranges of DCMU from 100 M to 1 M. Treatment times range from 15
min down to 30 sec. After treatment with DCMU the leaf Fv/Fm ratio drops to
<0.500, and never recovers.  From reading the literature it appears that
for most species it is quite difficult to get the DCMU absorbed into the
leaf tissue.  Perhaps since these plants are marine, the DCMU is rapidly
adsorbed.  I can't reliable dose the treatments much below 1 M. 

An example of the results for 30 sec in the 1 M solution, before exposure
the Fv/Fm ratio was .717, then after exposure it dropped to .579 after 30
min, .512 after 1 hour.  The plant does not appear to recover from the DCMU
treatment. These results are all before the plant is exposed to any form of
stress.

The 100 M DCMU is mixed with 1% Tween and 1% ethanol in seawater. 

Am I doing something wrong in my procedure ?

Any suggestions for DCMU treatment which will not effect the Fv/Fm ratio ?


Kind regards

Peter




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