An improved method to measure spatial variation in root respiration:: application to the taproot of a young peach tree Prunus persica

This paper presents an improved method to measure the local root respiration, by suspending them in a gel which could be sampled using an oxygen microelectrode. The effect of gel type on the oxygen diffusion and on transport of oxygen from the shoot to the root was studied. The local root respiration rates were estimated by fitting models for oxygen diffusion and consumption to the measured oxygen profile data obtained with the microelectrodes. The best fits to our experimental data were obtained with a model which describes oxygen radial diffusion, root consumption, and microbial consumption that declines with distance from the root. We applied this method along the taproot of Prunus persica (L.) Batsch. Local respiration level was consistent with root system respiration rate estimated in other plants of similar age and dimension, as measured by conventional gas chromatography. In accordance with published results, which have only been reported on primary structure respiration, the specific respiration rate was at a maximum in the elongating apical zone; it then decreased with distance from the root tip up to the root hair zone, where it increased.