Dehydrozaluzanin C, a natural sesquiterpenolide, causes rapid plasma membrane leakage

Dehydrozaluzanin C, a natural sesquiterpene lactone, is a weak plant growth inhibitor with an I-50 of about 0.5 mM for lettuce root growth. It also ca uses rapid plasma membrane leakage in cucumber cotyledon discs. Dehydrozalu zanin C is more active at 50 mu M than the same concentration of the herbic ide acifluorfen. Symptoms include plasmolysis and the disruption of membran e integrity is not light dependent. Reversal of its effects on root growth was obtained with treatment by various amino acids, with histidine and glyc ine providing ca. 40% reversion, The strong reversal effect obtained with r educed glutathione is due to cross-reactivity with DHZ and the formation of mono- and di-adducts. Photosynthetic, respiratory and mitotic processes, a s well as NADH oxidase activity appear to be unaffected by this compound. O ur results indicate that dehydrozaluzanin C exerts its effects on plants th rough two different mechanisms, only one of which is related to the disrupt ion of plasma membrane function. (C) 1999 Elsevier Science Ltd. All rights reserved.