Dynamics of oxygen and carbon dioxide in rhizospheres of Lobelia dortmanna - a planar optode study of belowground gas exchange between plants and sediment.

Root-mediated CO2 uptake, O2 release and their effects on O2 and CO2 dynamics in the rhizosphere of Lobelia dortmanna were investigated. Novel planar optode technology, imaging CO2 and O2 distribution around single roots, provided insights into the spatiotemporal patterns of gas exchange between roots, sediment and microbial community. In light, O2 release and CO2 uptake were pronounced, resulting in a distinct oxygenated zone (radius: c. 3 mm) and a CO2 -depleted zone (radius: c. 2 mm) around roots. Simultaneously, however, microbial CO2 production was stimulated within a larger zone around the roots (radius: c. 10 mm). This gave rise to a distinct pattern with a CO2 minimum at the root surface and a CO2 maximum c. 2 mm away from the root. In darkness, CO2 uptake ceased, and the CO2 -depleted zone disappeared within 2 h. By contrast, the oxygenated root zone remained even after 8 h, but diminished markedly over time. A tight coupling between photosynthetic processes and the spatiotemporal dynamics of O2 and CO2 in the rhizosphere of Lobelia was demonstrated, and we suggest that O2 -induced stimulation of the microbial community in the sediment increases the supply of inorganic carbon for photosynthesis by building up a CO2 reservoir in the rhizosphere.

Impact of age and body site on adult female skin surface pH.

BACKGROUND: pH is known as an important parameter in epidermal barrier function and homeostasis. AIM: The impact of age and body site on skin surface pH (pH(SS)) of women was evaluated in vivo. METHODS: Time domain dual lifetime referencing with luminescent sensor foils was used for pH(SS) measurements. pH(SS) was measured on the forehead, the temple, and the volar forearm of adult females (n = 97, 52.87 ± 18.58 years, 20-97 years). Every single measurement contained 2,500 pH values due to the luminescence imaging technique used. RESULTS: pH(SS) slightly increases with age on all three investigated body sites. There are no significant differences in pH(SS) between the three investigated body sites. CONCLUSION: Adult pH(SS) on the forehead, the temple and the volar forearm increases slightly with age. This knowledge is crucial for adapting medical skin care products.