THE EFFECT OF A MESOPHYLL FACTOR ON THE SWELLING OF GUARD-CELL PROTOPLASTS OF COMMELINA-COMMUNIS L

The effect of white, red and blue light on the swelling of guard cell protoplasts of Commelina communis has been investigated. White light and blue light caused protoplasts to swell but red light had no effect. Mesophyll cells were isolated from leaves of Commelina and incubated in buffer solution for one hour. The cells were then removed from the solution by centrifugation and the supernatant incubated with guard cell protoplasts. The supernatant from mesophyll cells incubated in white light caused enhanced swelling of guard cell protoplasts exposed to white light. Supernatant from mesophyll cells previously incubated in red light also caused protoplast swelling in the dark. Supernatant from mesophyll previously incubated in blue light had no effect on the protoplasts in the dark. Our results indicated that the mesophyll cells of Commelina leaves produce a soluble compound which causes swelling of isolated guard cell protoplasts. This factor appears to be made when the mesophyll is exposed to white or red light but not in darkness or when the cells are exposed to blue light. We observed that the stomata in the intact leaf of Commelina opened in response to blue and red light to about the same extent. Our results indicate that blue light is perceived by stomata at the guard cell itself whereas red light is sensed by the mesophyll and its effect transmitted to the guard cell by diffusion of the soluble factor to the stomata.