Final answer:
A decrease in plasma concentrations of ADH will result in decreased water reabsorption by the tubule system of the kidney.
Step-by-step explanation:
A decrease in plasma concentrations of ADH will result in a decreased water reabsorption by the tubule system of the kidney. ADH, also known as vasopressin, causes the insertion of water channel proteins, called aquaporins, into the cell membrane of renal collecting tubules. This increases the water permeability of the cells, leading to more reabsorption of water into the bloodstream. When ADH levels decrease, the aquaporins are removed, resulting in decreased water reabsorption and increased water excretion from the body.