Some Physiological Effects and The Possible Mechanism of Action of Juglone in Plants.

Abstract

The effects of juglone, an allelochemical from Juglans nigra, on cell elongation, respiration, protein content and α-amylase activity induced by gibberellin in aleurone cells, and its interactions with SH-groups in amino acids, peptides, proteins and plant extracts, were studied. Juglone inhibited cell elongation in the epicotyls of etiolated pea cv. Progress seedlings by 50 and 80%, and it inhibited the elongation of coleoptiles of etiolated barley cv. Delta seedlings by 75 and 96% at 10-4 and 10-3 M, resp. Root cell elongation in both species was inhibited to an even greater extent. Juglone solution at 10-3 M significantly decreased respiration (O2 uptake) in roots of peas and Lactuca scariola var. sativa [L. serriola or lettuces?] 10 and 30 min after the start of treatment, and completely reduced O2 uptake after 2 and 6 h, resp. At this concn, juglone also decreased the content of total soluble protein and α-amylase activity induced by gibberellin by 74% and 78%, resp., in the aleurone cells of barley embryoless half-seeds. In addition, it reacted with the SH-groups in cysteine, glutathione and bovine serum albumin, and decreased the level of SH-groups in crude extracts from germinated barley seeds and epicotyls of etiolated pea seedlings by 60 and 55%, resp. It was concluded that juglone may be a metabolic inhibitor which prevents many (if not all) physiological and biochemical processes involving SH-groups in compounds such as amino acids, peptides and enzymes.