The effect of ethrel on nodulation inPisum sativum L.

Summary Nodulation of inoculated pea plants was severely inhibited when ethrel (2-chloroethane phosphonic acid) was applied to the roots. The inhibition was evident at ethrel concentrations of 2 ppm and above. Ethrel applied to the foliage at 10 ppm also depressed nodulation. At least part of the effect of ethrel on nodulation came from its inhibition of root growth. Nodulation was inhibited on half of a divided root system treated with ethrel, while there was no inhibition on the neighbouring untreated half.