cereal nitrogen fixation

Thomas Bjorkman Thomas_Bjorkman at cornell.edu
Thu Feb 4 12:54:10 EST 1993


In article <C1uFAz.2An at ccu.umanitoba.ca> Euan R. Taylor,
etaylor at ccu.umanitoba.ca writes:
>A second question, relating to a naive (very) experiment we did some
time ago.
>If you plant surface sterilised seeds in autoclaved soil, growth is about
>1 1/2 weeks behind that of regular seeds in regular soil. What do you
>think I could be driving off in the soil tthat might cause this (NH4,
>oxygen, ?) we didn't do the other combinations at the time, as I say it
>was a very naive experiment that we set up last thing before christmas,
>just out of interest.

Surface sterilizing seeds makes them leaky, and generally reduces vigor
of the seedling (e.g. delays emergence).  Autoclaving soil gives you all
kinds of weird and wonderful chemical reactions that don't usually
happen.  Some of these apparently yield compounds that inhibit plant
growth.  It is often the case that planting surface-sterilized seed is
autoclaved soil produces sick plants.  The reason is pretty obvious:  a
weak host, lots of nutrients available and no competition.  You couldn't
make it much more inviting for pathogens.  Unless the soil is infested
with Pithium, Rhizoctonia or another vicious pathogen, you will do better
planting untreated seed into unsterilized soil.  Work with the microflora
instead if fighting it.

I guess from the  thread that you are studying soil bacteria, so this
suggestion may not be appropriate for you.  If you really need sterile
natural soil, you might look into microwaving it.  It is possible to
sterilize soil without much heating by microwaving in short bursts.



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