Induction and Development of Increased Ion Absorption in Corn Root Tissue

Abstract

Washing excised or intact primary roots of corn (Zea mays L., WF9 x M14) in aerated distilled water or dilute salt solutions for 2 hours induced doubling of the rate of accumulation of various nutrient ions and solutes. This response to washing depended upon aerobic metabolism, but involved no increase in aerobic respiration. Excision of root tissue was not required as the effect could be obtained with intact root systems. Increased phosphate absorption followed after a lag period of 30 to 40 minutes and continued for 6 hours before leveling off at about 3.5 times the initial rate. Chloramphenicol was not inhibitory to the development of increased absorption, while inhibitors of RNA and protein synthesis were. Auxins and kinetin were also inhibitory, but so was the antiauxin, 2,4,6-trichlorophenoxyacetic acid.Kinetic analyses of phosphate and potassium ((86)Rb) absorption showed no change in apparent Michaelis constant. Electron microscopic examination and analysis for membrane protein and lipid-phosphate content after washing showed no proliferation of membrane or other changes in cell structure and composition. It appears that washing augments or activates existing membrane transport mechanisms by processes involving protein synthesis.