Claim and why it matters
The explanation argues that most fruits and plant foods are not naturally salty because plant and animal physiology evolved around different key ions and because high sodium levels can harm many land plants. The explanation also points to halophytes (salt-tolerant plants) as a reason naturally salty plant foods exist in some cases.
Background: sodium-linked functions in animals vs potassium-linked regulation in plants
The explanation links sodium in animals to nervous system function and to maintaining extracellular fluid (fluid outside cells). Because sodium is needed for these functions, the explanation argues that animals evolved behaviours that seek and store salt.
For plants, the explanation links potassium to internal regulation processes that support growth and cell pressure. The explanation also states that high sodium levels can be toxic for many land plants, which limits naturally sodium-rich taste in typical fruits and plant foods.