Abstract

The germination of seeds of 48 plant species was not inhibited by exposure to aqueous leachate solutions from viable seeds of crownvetch (Coronilla varia L.). However, for most species tested freeze-dried ‘Penngift‘ crownvetch leachate at dilutions up to 1:2,000 (wt./v.) induced drastic shortening of the shoot and root and resulted in almost complete elimination of root hair growth. Root tips were necrotic and roots thickened. Roots of some test species germinated on blotters moistened with crownvetch leachate were negatively geotropic. Seedlings of some species were adversely affected at leachate dilutions of 1:10,000. The osmotic pressure of a 1:200 solution of leachate was approximately 0.4 bar. This is too low to account for the effects noted on shoots and roots. Leachate from viable crownvetch seeds was more phytotoxic than that from viable sweetclover (Melilotus alba) seeds; this, in turn, was more phytotoxic than leachate from aged (weathered) red clover (Trifolium pratense L.) seeds of low germination and vigor. The phytotoxic compounds in crownvetch leachate appear to be low molecular weight phenols and polyphenols but differ from those in leachates from red clover and sweetclover.

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