Grass leaves may be wrinkled or fused at the tips. The oldest leaves on young dicots may be gnarled or squared off. Three typical steps 1. Inactivation typical changes to the molecule by biochemical processes. Oxidation, hydrolosis, reduction, deamination, imethylation and ring cleavage 2.
Crops are susceptible to herbicide injury when very young or as reproductive structures are forming.
Differentials in plant height can provide selectivity by using directed sprays or wipe-on devices. Differential retention and wetting can account for selectivity between plants with markedly different leaf orientation and surface wax. Adjuvants added to foliar sprays can alter this type of selectivity. Differences in rates of herbicide penetration, translocation, or deactivation may account for selectivity. In some cases, differential metabolism from an inactive to an active compound accounts for selectivity.