The CO2 response of Vicia guard cells acclimates to growth environment

Stomata of growth chamber-grown Vicia faba leaves have an enhanced CO 2 response, measured as change in stomatal aperture, compared to stomata of greenhouse-grown leaves. Reciprocal transfer experiments showed that the stomatal response to CO 2 acclimated to the growing environment. Stomata of growth chamber-grown leaves transferred to a greenhouse lost their high CO 2 sensitivity within 2-3 d while stomata of greenhouse-grown leaves transferred to a growth chamber acquired a high CO 2 sensitivity within 5-7 d. Experiments measuring the CO 2 responses of stomata in detached epidermis showed that growth chamber and greenhouse-grown stomata have the same contrasting CO 2 sensitivity observed in the intact leaf, indicating that the responses reflect intrinsic guard cell properties. The acclimation properties of the CO 2 response of guard cells have implications for the understanding of stomatal function under the predicted increases in atmospheric CO 2 .