J. Plant Physiol. 158. 1299–1305 (2001)  Urban & Fischer Verlag http://www.urbanfischer.de/journals/jpp Oxidative stress during phosphate deficiency in roots of bean plants ( Phaseolus vulgaris L.) Izabela Juszczuk 1 , Eligio Malusà 2 , Anna M. Rychter 1 * 1 University of Warsaw, Institute of Experimental Plant Biology, Miecznikowa 1, 02-096 Warsaw, Poland 2 Experimental Institute of Plant Nutrition, via Ormea 47, 10125 Turin, Italy Received January 11, 2001 · Accepted May 11, 2001 Summary The oxidative stress symptoms were studied during phosphate deficiency. Prolonged phosphate starvation of bean plants (Phaseolus vulgaris L.) and severe decrease of inorganic phosphate con- centration resulted in increased lipid peroxidation and hydrogen peroxide concentration in root tis- sues. The ratio of reduced to total ubiquinone was also higher in whole roots and isolated mitochon- dria from the roots of phosphate-deficient plants. No effect of phosphate deficiency on ascorbate per- oxidase and superoxide dismutase activities was detected. However, the activities of catalase and total peroxidase were higher in extracts of phosphate-deficient roots compared to control roots. These results indicate that phosphate starvation is an abiotic stress that imposes an oxidative stress in bean root cells. The role of alternative oxidase in stabilizing the reduction level of ubiquinone, and thus preventing active oxygen species formation, is discussed. Key words: bean – catalase – hydrogen peroxide – mitochondria – peroxidases – ubiquinone Abbreviations: AOS active oxygen species. – Pi inorganic phosphate. – Q ubiquinone Introduction Accumulation of active oxygen species (AOS), resulting in oxidative stress, is a common feature of several types of abiotic stress (Elstner and Osswald 1994, Bartosz 1997), including excess or deficiency of nutritional elements (Cak- mak 1994, Caro and Puntarulo 1996). In plant tissues, photo- synthesis and respiration are considered to be the major pro- cesses involved in AOS formation (Asada and Takahashi 1987, Puntarulo et al. 1991). Production of AOS also occurs in * E-mail corresponding author: anna@rychter.com endoplasmic reticulum, microbodies, and plasma mem- branes (McKersie and Leshem 1994). In nonphotosynthetic tissues, AOS produced in mitochondria have been suggested to be the most important source of cytosolic H 2 O 2 (Puntarulo et al. 1991). AOS can react with membrane lipids causing their peroxidation, which leads to membrane damage. Intra- cellular membrane damage can affect respiratory activity of mitochondria (Scandalios 1993). Under normal growing conditions, AOS are maintained at a non-damaging level by several antioxidant compounds and enzymes, which either scavenge or utilize them (Elstner and Osswald 1994, McKersie and Leshem 1994). However, these 0176-1617/01/158/10-1299 $ 15.00/0