Question

Stoma opens when -

1)guard cell swell due to an increase in their water potential

2)guard cell swell by endosmosis due to influx of proton

3)guard cell swell by endosmosis due to efflux of potassium ion

4)guard cells swell due to a decrease in their water potential

Answer 1

Option 4 is correct
Stoma opens when guard cells swell due to a decrease in their water potential

When there is light, potassium ions are pumped in, which results is lowering of the water potential inside the guard cells. Consequently, there is an influx of water resulting in the turgidity of the guard cells and opening of the stoma.