Question

why will mint leaves left on the window wilt after a few days while the mint leaves on the plant be healthy.

Answer 1

The mint leaves that are attached to the plant get undisturbed supply of water and minerals absorbed by the roots and transported by xylem. Thus they can be able to carry on all of their normal body processes. But the leaves when detached from the plants are not able to get water supply. Moreover as kept near the windows, water is getting evaporated from the leaves very fast. For this reason they get wilted after few days without water supply.