Pj. Gregory et P. Hinsinger, New approaches to studying chemical and physical changes in the rhizosphere: an overview, PLANT SOIL, 211(1), 1999, pp. 1-9
The past decade has seen the rapid development of new techniques that have
revealed substantial changes in soil physical and chemical properties in th
e rhizosphere compared to the bulk soil. This brief overview focuses on som
e examples of recently developed, innovative techniques now available and i
ndicates the technical developments required for the future. The developmen
t of non-invasive imaging allied with computed tomography has begun to allo
w the study of root systems in situ and the measurement of localized uptake
of water. Further development is still required to disaggregate the simult
aneous changes in bulk density and water content that may occur as roots oc
cupy new soil volumes, but resolution of 0.1 mm is now feasible in scanning
times of less than 1 h thereby allowing dynamic processes to be measured.
Changes in surface tension and composition of solutions close to roots, and
of pH, can now be measured with a variety of techniques. Temporal and spat
ial changes of pH can be measured with micro-electrodes and dye indicator/a
gar gel techniques have allowed quantitative estimates of H+ fluxes albeit
in artificial systems. Novel micro-sampling techniques are under developmen
t to quantify rhizosphere changes. So far these techniques have rarely been
applied in soils but innovative sampling and analytical techniques should
soon allow such studies.