Tropism.

By using an axonometer .

Tropisms and nastic movements are both plant responses to external stimuli. however tropisms are depend on the direction of the stimulus nastic movements do not depend on the direction of a stimulus

The nastic movements of plants keep the shoot in contact with light and roots in the dark to adapt the plants from adverse conditions of root and shoot growth.

no,because when water moves in a plant cell,it moves from a region of higher concentration(vacuole) to another plant cell.this movements is known as active transport because it against the concentration gradient.