What is the oxygen status of plant tissue? Now we know!

What is the oxygen status of plant tissue? Now we know!

Adequate tissue O2 supply is crucial for plant function, and now we know how the environment influences tissue O2 status. We also know how the tissue O2 status differs in various tissue at various points in time - if you would like to see as well, get the paper from here (an Evans Review published in Functional Plant Biology).

We aimed to identify the environmental conditions and plant characteristics that affect plant tissue O2 status. We extracted data and performed meta-analysis on >1500 published tissue O2 measurements from 112 species. Tissue O2 status ranged from anoxic conditions in roots to >53 kPa in submerged, photosynthesising shoots. Using information-theoretic model selection, we identified ‘submergence’, ‘light’, ‘tissue type’ as well as ‘light × submergence’ interaction as significant drivers of tissue O2 status. Median O2 status were especially low (<50% of atmospheric equilibrium) in belowground rhizomes, potato (Solanum tuberosum) tubers and root nodules. Mean shoot and root O2 were ~25% higher in light than in dark when shoots had atmospheric contact. However, light showed a significant interaction with submergence on plant O2, with a submergence-induced 44% increase in light, compared with a 42% decline in dark, relative to plants with atmospheric contact. During submergence, ambient water column O2 and shoot tissue O2 correlated stronger in darkness than in light conditions. Although use of miniaturised Clark-type O2 electrodes has enhanced understanding of plant O2 dynamics, application of non-invasive methods in plants is still lacking behind its widespread use in mammalian tissues.

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Numerous studies have used submergence as a treatment to impose tissue hypoxia in plants. This approach might work, but only in darkness! If the plant is submerged in light, tissue O2 status increases from a mean of 17 kPa to 24 kPa, which is actually hyperoxia. So please be careful with interpretation of data from such studies!...