Light and stomatal function: blue light stimulates swelling of guard cell protoplasts

Zeiger, E.; Hepler, P. K.

doi:10.1126/science.196.4292.887

Onion guard cell protoplasts swell when illuminated with blue light. The response is a 35 to 60 percent increase in volume and is dependent on potassium ion. Epidermal cell protoplasts do not swell under the same conditions. It is postulated that a membrane-bound blue photoreceptor mediates a direct response of guard cells to light.