Figure 6.

The effect of nitrate on induction of CYP79A1 and CYP71E1 catalytic activity and cyanide potential in different parts of 5-week-old sorghum plants. A, Microsomes were prepared from different plant parts, and their ability to convert ¹⁴C-labeled l-Tyr to p-hydroxymandelonitrile was analyzed by phosphor image-TLC of enzymatic reaction mixtures as described in “Materials and Methods.” ○, No microsomes added; +, positive control using microsomes prepared from 2-d-old sorghum seedlings; CHO, p-hydroxybenzaldehyde (degradation product of p-hydroxymandelonitrile); OX, Z-p-hydroxyphenylacetaldehyde oxime; and TYR, l-Tyr (which stays at the origin of the TLC plate). B, The cyanide potential of leafs and stems measured after growth in the absence and presence of KNO₃ as described in “Materials and Methods.” In all experiments shown, the induction period used was 12 d.