Decrease in stomatal density in plants due to continuing rise in CO2

Environmental stimuli, including elevated carbon dioxide levels, regulate stomatal development in plants; however, the key mechanisms mediating the perception and relay of the CO2 signal to the stomatal development machinery remain elusive.

To adapt CO2 intake to water loss, plants regulate the development of stomatal gas exchange pores in the aerial epidermis. A diverse range of plant species show a decrease in stomatal density in response to the continuing rise in atmospheric CO2. To date, one mutant that exhibits deregulation of this CO2-controlled stomatal development response, hic (which is defective in cell-wall wax biosynthesis), has been identified.

Here we show that recently isolated Arabidopsis thaliana β-carbonic anhydrase double mutants exhibit an inversion in their response to elevated CO2, showing increased stomatal development at elevated CO2 levels. We characterized the mechanisms mediating this response and identified an extracellular signalling pathway involved in the regulation of CO2-controlled stomatal development by carbonic anhydrases.

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