In a high osmolality medium, turgor drops and growth slows. The most rapid response is an increase in K + influx. Also, the level of putrescine, a divalent cation, drops. The net effect is increased osmolality with little change in intracellular ionic strength. The increase in K+ results in an increase in the anionic glutamate. Trehalose, which is neutral, also increases, and can contribute up to 20% of a cell’s osmolality. This is the last event to occur, and K + and glutamate decline. Macromolecular synthesis resumes at this point. Several compounds, if they are present externally, can also help a cell with high osmolality. Two are glycine betaine (the amino group of glycine is substituted with three methyl groups) and proline.