It has long been known that calcium ion antagonizes glyphosate, but it was not clear whether the stoichiometry of their interaction is 1:1 or 1:2. Two independent methods were used to determine which stoichiometry was the most probable. First, dose±response curves of barley (Hordeum vulgare L.) plants treated with glyphosate were determined in the presence of 0, 1.25, 2.5, 5 and 10 mM CaCl 2 . The doses of`free' glyphosate (not inactivated by calcium ion) were computed using the assumptions of 1:1 and 1:2 stoechiometries. The response curves were redrawn as a function of`free' glyphosate. Analysis showed that the 1:2 hypothesis could be rejected, whereas the 1:1 hypothesis was highly probable. Second, kinetics of glyphosate penetration into barley leaves were determined in the presence of 0, 2.5 and 10 mM CaCl 2 . The concentrations of`free' glyphosate were computed as above. The kinetics of glyphosate penetration at these concentrations were established and were compared to the kinetics of glyphosate penetration in the presence of CaCl 2 . Again, the 1:2 hypothesis was rejected, whereas the 1:1 hypothesis was more probable. These results strongly suggest that the stoichiometry of the Ca 2+ :glyphosate association is 1:1 in deposit residuals on the leaf surface.

To quantify the variability and dynamics of bacterial populations on field-grown broad-leaved endive (Ckhnrium endivia cv. Samy) destined for ready-to-use processing, plants were sown at three dates in 1990 for cultivation during the autumn season in southern France. Densities of populations of total, fluorescent pseudomonad and pectolytic bacteria were determined for entire seedlings in the greenhouse and for outer and inner leaves of plants in the field throughout the season until harvest. On seedlings from the greenhouse, bacteria were always detected but fluorescent and pectolytic bacteria were only sporadically detected and generally composed less than 0.1% of the total population. In the field there were significant differences in total, fluorescent and pectolytic bacterial populations on outer and inner leaves, among different plants of the same age, and among inner leaves sampled at the three different dates of harvest. The variability observed suggests that it is reasonable to pursue development of cultural or industrial sorting methods to reduce the microbial load of endive destined for ready-to-use processing.