Phototropins and not cryptochromes mediate the blue light-specific response of stomatal conductance but both promote photosynthesis and transpiration under full sunlight in Arabidopsis

BOCCALANDRO, HERNÁN E.; GIORDANO, CARLA V.; PLOSCHUK, EDMUNDO; PICCOLI, PATRICIA N.; BOTTINI, RUBÉN; CASAL, JORGE J.

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Año: 2011 vol. 158 p. 1 - 10

0032-0889

Leaf epidermal peels of Arabidopsis mutants lacking either phototropins 1 and 2 (phot1, phot2) or cryptochromes 1 and 2 (cry1, cry2) exposed to a background of red light show severely impaired stomatal opening responses to blue light. Since phot and cry are UV- A/blue light photoreceptors, they may be involved in the perception of the blue light-specific signal that induces the aperture of the stomatal pores. In leaf epidermal peels the blue-light specific effect saturates at low irradiances and it is therefore considered to operate mainly under the low irradiance of dawn, dusk or deep canopies. Conversely, we show that both phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration and photosynthesis particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely non-stomatic. While the stomatal conductance phenotype of phot1 phot2 was blue-light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid (ABA) were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of ABA levels.phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration and photosynthesis particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely non-stomatic. While the stomatal conductance phenotype of phot1 phot2 was blue-light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid (ABA) were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of ABA levels.