What function do Parathion and Malathion serve in agriculture?

Parathion and Malathion serve as pesticides due to their role as cholinesterase inhibitors. These chemicals are specifically designed to target and disrupt the normal function of the enzyme acetylcholinesterase, which is essential for breaking down the neurotransmitter acetylcholine in the synaptic cleft. When acetylcholine is not adequately metabolized, it accumulates, leading to overstimulation of the cholinergic receptors. This effect is particularly detrimental to pests, effectively immobilizing or killing them.

As pesticides, both Parathion and Malathion are used to protect crops from insect infestations by leveraging their neurotoxic properties against agricultural pests. Their application can significantly enhance crop yield by controlling pest populations, making them critical components in agricultural practices.

Other options, like fertilizers, irrigation enhancers, and soil amendments, do not define the action of Parathion and Malathion, as they do not contribute to promoting plant growth or improving soil quality in the same way that pesticides do. Thus, option C is the correct identification of their function in agriculture.