The CO2 response of Vicia guard cells acclimates to growth environment

Stomata of growth chamber-grown Vicia faba leaves have an enhanced CO2 response, measured as change in stomatal aperture, compared to stomata of greenhouse-grown leaves. Reciprocal transfer experiments showed that the stomatal response to CO2 acclimated to the growing environment. Stomata of growth chamber-grown leaves transferred to a greenhouse lost their high CO2 sensitivity within 2-3 d while stomata of greenhouse-grown leaves transferred to a growth chamber acquired a high CO2 sensitivity within 5-7 d. Experiments measuring the CO2 responses of stomata in detached epidermis showed that growth chamber and greenhouse-grown stomata have the same contrasting CO2 sensitivity observed in the intact leaf, indicating that the responses reflect intrinsic guard cell properties. The acclimation properties of the CO2 response of guard cells have implications for the understanding of stomatal function under the predicted increases in atmospheric CO2.