Assertion: Increased turgor in guard cells opens stomata.
Reason: Rings of cellulose microfibrils prevent the width of the guard cells from swelling, and only allow the extra turgor pressure to elongate the guard cells.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.