On 16 August at 10:15 Pirko Jalakas will denfend his doctoral thesis „Unravelling signalling pathways contributing to stomatal conductance and responsiveness“ .
Senior Research Fellow, PhD Mikael Johan Brosché
Senior Research Fellow, PhD Ebe Merilo
PhD Caspar Chater, UNAM/University of Sheffield
Survival of plants in the changing environment depends largely on stomata, small pores surrounded by a pair of specialized guard cells on the aerial surface of plants. Stomata control gas exchange between the leaf and atmosphere – uptake of CO2 for photosynthesis and loss of water through transpiration. Plant growth, stress-related water management and production depend on the appropriate control of stomatal conductance, one of the most important leaf physiological traits. Rapid changes in the stomatal aperture width and changes in the number of stomata (stomatal density) on a longer timescale both affect stomatal conductance and enable to regulate it according to endogenous and environmental cues. We studied the role of plant hormone abscisic acid (ABA) in controlling stomatal conductance and found that reduced leaf ABA concentration led to higher stomatal conductance. This was associated with wider stomatal aperture width and increased stomatal density of these plants. ABA-deficient plants thus lost more water to the atmosphere, but were still able to respond to environmental changes with stomatal closure. We found that stomatal guard cells and phloem companion cells were important sources of ABA. We showed that OST1, a key positive regulator of ABA signalling, was important in stomatal responsiveness to environmental factors and ABA, but it was not involved in regulating stomatal development. Stomatal regulation by a farnesylating protein ERA1, which is suggested to be involved in ABA signalling, was also studied. We revealed that ERA1 is involved in determining the stomatal conductance and mediating the blue light-induced opening response. Understanding the mechanism of stomatal regulation gives information for breeding crop plants productive in different climatic conditions. The focus is on developing more water use efficient plants with reduced stomatal conductance without compromising in photosynthesis and ultimately, in crop yields.