Thesis topic: Light dependent stomatal osmoregulation

abax_edited-8Master (Pro Gradu) thesis subject available in Plant Biology

Thesis topic: Light dependent stomatal osmoregulation in Arabidopsis photoreceptor mutants

Background: Plants gain CO2 for photosynthesis through open stomata but reduce water loss by closing stomata. Stomatal opening in response to light depends at least on two pathways: photosynthesis stimulation and blue-light specific regulation. In the opening process, different photoreceptors located in guard cells are involved (Chen et al., 2012). In the osmoregulation of stomatal opening, potassium has been found to be the main osmoticum in Vicia faba (Fischer, 1968) but its accumulation is time-of-day-dependent (Amodeo et al., 1996). Other osmotica also contribute to the response.

stomata__KFig. Different amounts of potassium precipitation in guard cells under different conditions.

Objective: Potassium concentration in guard cells can be assessed by histochemical methods. A special staining based on cobalt causes precipitation of potassium inside guard cells. The amount of precipitate can be quantified from light microscope images. The aim is to compare the daily changes in potassium in two blue-light photoreceptor (cryptochromes and phototropins) Arabidopsis mutants (cry1cry2 and phot1phot2) under different light conditions. Plants would be irradiated by blue, green or red high power LED arrays, separately or in combinations (e.g. low irradiance blue light on a background of high irradiance red light).
Tentative schedule: 1) May 2014 growing plants and training. 2) June 2014 measurements. 3) July 2014 image- and data analysis.
Contacts: Pedro J Aphalo, pedro.aphalo@helsinki.fi, Fang Wang, fang.wang@helsinki.fi, Kurt Fagerstedt, kurt.fagerstedt@helsinki.fi

References

Amodeo G, Talbott L, Zeiger E. 1996. Use of potassium and sucrose by onion guard cells during a daily cycle of osmoregulation. Plant and cell physiology 37, 575-579.
Chen C, Xiao Y-G, Li X, Ni M. 2012. Light-regulated stomatal aperture in Arabidopsis. Molecular plant 5(3): 566-572.
Fischer R. 1968. Stomatal opening: role of potassium uptake by guard cells. Science 160(3829): 784-785.

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