Emerging technologies for non-invasive quantification of physiological oxygen transport in plants

Oxygen plays a critical role in plant metabolism, stress response/signaling, and adaptation to environmental changes (Lambers and Colmer, Plant Soil 274:7-15, 2005; Pitzschke et al., Antioxid Redox Signal 8:1757-1764, 2006; Van Breusegem et al., Plant Sci 161:405-414, 2001). Reactive oxygen species (ROS), by-products of various metabolic pathways in which oxygen is a key molecule, are produced during adaptation responses to environmental stress. While much is known about plant adaptation to stress (e.g., detoxifying enzymes, antioxidant production), the link between ROS metabolism, O-2 transport, and stress response mechanisms is unknown. Thus, non-invasive technologies for measuring O-2 are critical for understanding the link between physiological O-2 transport and ROS signaling. New non-invasive technologies allow real-time measurement of O-2 at the single cell and even organelle levels. This review briefly summarizes currently available (i.e., mainstream) technologies for measuring O-2 and then introduces emerging technologies for measuring O-2. Advanced techniques that provide the ability to non-invasively (i.e., non-destructively) measure O-2 are highlighted. In the near future, these non-invasive sensors will facilitate novel experimentation that will allow plant physiologists to ask new hypothesis-driven research questions aimed at improving our understanding of physiological O-2 transport.