Reactive oxygen species (ROS) play a significant role in plant growth, development, and interaction with biotic and abiotic environments (Alvarez et al., 1998; Blokhina et al., 2003). ROS have also been implicated as important regulatory and signaling elements in a variety of cellular processes (Foyer and Noctor, 2005). ROS are constantly produced during the course of photosynthesis and respiration, whereas redox homeostasis in the cell is tightly controlled by redundant protective mechanisms. Disruption of these protective mechanisms can cause oxidative stress, leading to oxidative damage and cell death. Measuring oxidative stress in the cell requires sensitive and robust assays for ROS detection, accurate quantitation, and measurements of intrinsic cell defense responses.

Measurement of ROS in living organisms carries a significant analytical challenge. Most ROS are highly reactive and short lived and therefore hard to detect in complex biological matrices. Additionally, ROS often are produced and/or detoxified in subcellular compartments, which requires detection methods directed to specific subcellular localization. ROS can be measured either directly or indirectly following the formation of oxidative by-products of lipids, proteins, or nucleic acids (a technique often called fingerprinting). Techniques to measure these reactive intermediates have been extensively reviewed (for a recent review, see Halliwell and Whiteman, 2004; Tarpey et al., 2004). Here we mainly focus on recent applications of these techniques to measure ROS in plants.