Reduction of non-ionic surfactant phytotoxicity by divalent cations

The non-ionic surfactants, Triton X-100 and Genapol C-80 (1 gl(-1)) in deio nised water, caused severe phytotoxicity when applied to bracts of poinsett ia (Euphorbia pulcherrima) with green leaves being less sensitive. Addition of calcium as calcium chloride or nitrate reduced surfactant-induced necro ses with increasing concentration. 10 mM calcium and higher prevented phyto toxicity caused by Triton X-100, 100 mM for Genapol C-80. Magnesium chlorid e was almost as effective as calcium, whereas 100 mM strontium chloride pre vented necroses by Triton X-100 but not by Genapol C-80. Potassium chloride showed no effect on surfactant toxicity. Results from trials with a changi ng sequence of surfactant and calcium salt application imply that calcium a cts in the droplet residue on the leaf surface and not within the leaf tiss ue. (C) 2000 Elsevier Science Ltd. All rights reserved.