Rapid-growth Responses of Corn Root Segments: Effect of Citrate-phosphate Buffer on Elongation

The effects of citrate-phosphate buffer on the elongation rate of 2 mm root segments of Zea mays L. was investigated under O2 and N2 conditions by comparing with the effects in non-buffered solution. The buffer at pH 7.0 has an inhibiting effect on the elongation rate of root segments. At pH 4.0 the buffer has a promoting effect on the elongation rate twice that of the H-ion concentration. Nitrogen experiments indicate that growth in neutral buffer is O2 dependent. On the other hand the acid-growth response of root segments in citrate-phosphate buffer appears to have two components, 1) a H-ion component which is partially inhibited by N2 and fluoride and 2) a citrate component which is inhibited in part by N2 but not by fluoride.