Shoot excision has no effect on net flux of protons, ammonium or nitrate in seedling roots of a conifer and three crop species

A high-flux region, 5 mm from the root tips of seedlings of coastal Douglas-fir (Pseudotsuga menziesii), soybean (Glycine max), zucchini (Cucurbita pepo) and pea (Pisum sativum), was monitored using a microelectrode ion flux measurement system, for changes in the net fluxes of H+, NH4+ and NO3− in response to shoot removal. In all species, careful excision of the seedling shoot had no significant effect on the net fluxes of H+, NH4+ or NO3− measured 5 mm from the root tip. Experiments were carried out for up to 80 min after shoot removal, and no temporal interactions were noted.