A novel approach to the in situ measurement of oxygen concentrations in the sapwood of woody plants

Abstract

to an oxygen deficit of 40-75% of air saturation. Oxygen concentration maxima and minima occurred early in the morning and in the afternoon, respectively, whereas xylem sap temperatures showed the reverse pattern. In the sapwood, hypoxia increased from the beginning of bud break until frondescence, when a deficit of 86% of air saturation marked the upper limit of oxygen depletion. There seemed to be no relationship between daily variations of oxygen concentration and xylem sap pressure. In summer, sap flow was a major determinant for the diurnal variation of dissolved oxygen concentration. Oxygen supply to the sapwood was determined by both radial influx into the trunk through intercellular gas spaces and transport of dissolved oxygen via xylem sap flow. Radial influx seemed to be favoured during night-time, when the trunk was warmer than ambient air. During daytime, the hypoxia of the sapwood rose and increased sharply in the evening, when sap flow velocity approximated zero. High temperature in the sapwood enhanced the respiratory oxygen consumption of the wood parenchyma while the supply of dissolved oxygen via the transpiration stream became ineffective.

New and Fast Method To Quantify Respiration Rates of Bacterial and Plankton Communities in Freshwater Ecosystems by Using Optical Oxygen Sensor Spots

“…A promising approach is a new type of optical electrodes, the so-called opt(r)odes, introduced into microbial research by Klimant et al (29). Optodes for oxygen, temperature, or pH profiles were successfully applied to invertebrates, e.g., sponges (18), to plant tissue, to sediments, and even to ice formation (16,20,32). The main advantages of optodes are that (i) they are used in noninvasive systems, (ii) no oxygen is consumed by the optode itself, (iii) measurements are possible over a temperature range wider than that for classical methods, (iv) short incubation times are sufficient to obtain reliable data, and (v) no mechanical stress, i.e., constant stirring of the samples, is imposed on bacteria.…”

Differences in morphological and physiological responses to water-logging between two sympatric oak species (Quercus petraea[Matt.] Liebl.,Quercus roburL.)

“…Lenticels of stems are permeable to water [31], strengthening the hypothesis that they play a significant role in water absorption. Lenticels could also play a major role in the oxygenation of shoots via import of O 2 into xylem sap, and then in the shoot via the transpiration flux [18,27,28,46]. They probably are the key trait explaining the differences of tolerance among the two species, and their functional role needs to be carefully assessed.…”

Is oxygen involved in beech (Fagus sylvatica) red heartwood formation?

“…Recent developments in sensor technology using nonoxygen consuming optodes (Holst et al 1997) allow measurement of oxygen concentrations directly in living stems (Gansert et al 2001;del Hierro et al 2002). In the present study, we used this technique to test the hypothesis of oxygen involvement in red heart formation in beech.…”