root nodules

Kathleen Archer Kathleen.Archer at trincoll.edu
Fri Oct 5 07:04:40 EST 2001


Hi Folks,
I've used garden peas and inoculum to generate abundant nodules 
easily.  You can get good nodules in 5-6 weeks.
The key thing is that the inoculum should be fresh - purchased for that 
year's use and kept in the fridge.  I guess it has a limited life span,
so 
perhaps your inoculum is old.
I soak the peas overnight in running water to hydrate, roll them in 
inoculum and plant in half perlite/half vermiculite in 4" pots, about 4 
or 
5 seeds per pot.  Peas like it a little cool, so if you can give them
18C 
to grow that's great.  But they'll probably do well at room temp 
too.  After 5 weeks, pull out the plants in one pot to check.  You can 
gently wash away the planting medium by swishing the roots in a pan of 
water.  The nodules will be about the size of half a rice grain, maybe
2-4 
mm in diameter.  They aren't obvious until you start cleaning the medium 
away from the roots, and then suddenly you realize there are dozens, 
potentially up to a hundred.

They will produce more and bigger nodules if you do not fertilize the 
plants after the first week.  The peas need a little something to grow
on 
until nodules form, so I fertilize with a liquid fertilizer the first
week 
after germination, but after that give only water.  A nice lab exercise, 
which I believe I modified from one obtained from this group (check the 
archives!) is to grow peas with and without nitrogen fertilizer, and 
compare the # or mass of nodules formed in each treatment.
You can obtain good inoculum from Johhny's Select Seeds 
(http://www.johnnyseeds.com/).
Goood luck,
Kathleen Archer

******************************
Kathleen Archer
Dept. Biology
Trinity College
Hartford, CT 06106
Ph: (860)297-2226
kathleen.archer at mail.trincoll.edu
*******************************

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