Mapping meristem respiration of Prunus persica (L.) Batsch seedlings: potential respiration of the meristems, O-2 diffusional constraints and combined effects on root growth

Root system architecture partially results from meristem activities, which themselves depend on endogenous and environmental factors, such as O-2 depl etion. In this study, meristem respiration and growth was measured in the r oot systems of three Prunus persica (L.) Batsch seedlings. The spatial dist ribution of meristem respiration within the root system was described, and the relationship between the respiration rates and meristem radii was analy sed, using a model of radial O-2 diffusion and consumption within the root. Histological observations were also used to help interpret the results. Re spiration rates were linearly correlated to the root growth rates (rho(2) = 0.9). Respiration reached values greater than 3.5 x 10(-13) mol O-2 s(-1) for active meristems. The taproot meristem consumed more O-2 than the rest of the entire root system meristems. Similarly, the first order lateral mer istems used more O-2 than the second order ones. A near hyperbolic relation ship between respiration rates and meristem radii was observed. This can be explained by a model of radial O-2 diffusion and consumption within the ro ot. Therefore, only one maximum potential respiration rate and one O-2 diff usion coefficient was estimated for all the meristems.