Host Sanctions
Legume plants don't pay nitrogen-fixing bacteria for showing up - they pay for nitrogen delivered.
Nodules with lazy bacteria that consume plant sugars without fixing proportionate nitrogen get starved of carbohydrates.
In legume-Rhizobium mutualisms, plants can sanction poor-performing bacterial partners by reducing resource allocation to ineffective nodules. Experimental studies show plants preferentially send carbohydrates to effective nodules while starving ineffective ones. This sanctioning prevents exploitation - bacteria that don't fix nitrogen don't receive compensation.
Similarly, plants can abort mycorrhizal associations with fungi providing insufficient nutrients, redirecting resources to more beneficial fungal partners. This partner choice and post-colonization control gives plants leverage to enforce mutualistic service.
Business Application of Host Sanctions
Legume plants don't pay nitrogen-fixing bacteria for showing up - they pay for nitrogen delivered. Organizations need analogous monitoring. Rolls-Royce's Power by the Hour solved this by instrumenting engines with sensors, creating the organizational equivalent of the plant's nodule monitoring system.