Take four pots having mint plant with same sizes and then apply 2% salt to pot no.1, then apply 5% salt to pot no.2, apply 10% salt to pot no.3, and apply 15% salt to pot no.4. After a 1 week or 2, see the growth of the mint plants. You will notice some mint plants are not effected to salt concentration because they are present in low quantity whereas some plants experience stunted growth due to higher concentration of salt which is unbearable for the mint plant.
There are guard cells surrounding each stoma that cause them to open or close throughout the life cycle of the plant. This occurs in response to water and ions concentration in the plant cell.