Rapid Method for Measuring Changes in pH and Reducing Processes Along Roots of Intact Plants

Abstract

Roots of intact plants ( Helianthus annuus; Calathea warscewizii; Zea mays ) were embedded in an agar medium (0.75%) containing nutrient solution and either bromocresol purple (pH indicator) or BPDS (chelator for Fe II ). Around the apical root zones of Fe deficient sunflower plants, enhanced reduction of Fe III (formation of red coloured Fe II (BPDS) 3 ) and increased proton efflux (i.e. acidification of the medium) could be observed within a few hours. Under Fe deficiency, enhanced reduction of manganese (MnFe IV ) could also be demonstrated in the same root zones when the roots were embedded in agar with MnCO 2 . In the agar media with bromocresol purple the effect of the source of nitrogen (NC 3 - and NH 4 + respectively) on pH changes along the roots can be demonstrated within a few hours. Along corn roots with NCO 3 - supply the pH rises steeply only around certain zones of the seminal root. The pH changes along roots (either induced by the source of nitrogen or the Fe nutritional status) can also be directly measured by inserting microelectrodes into the agar media. With this agar method more detailed information can be obtained on the response of the various root zones of intact plants to either the nutritional status of the plant or to the supply of different nutrients.