Mesophyll conductance and water-use efficiency of grain crops

Summary

Efficient use of water is the most pressing environmental issue facing the Australian grain industry.  While significant research effort has been employed to improve water-use efficiency (WUE), a number of leaf traits that influence leaf intrinsic WUE (A/gs; the ratio of photosynthesis to stomatal conductance) have strong potential to provide WUE gains.  Our recent study on Barley genotypes has revealed considerable variation in the ease with which CO2 diffuses within a leaf (mesophyll conductance; gm), and genotypes with high gm had enhanced A/gs and WUE.  Using state-of-the-art stable isotopic laser-based approaches, this project will (1) screen existing Australian grain genotypes to determine the degree of variability in gm, and its influence on A/gs, under controlled-environment conditions; (2) determine the degree of sensitivity of gm in grain genotypes to environmental parameters such as temperature, irradiance, water and nitrogen availability; (3) determine the degree to which leaf-level changes in gm affect crop-scale WUE and yield in the field

Supervisor(s)

Dr Margaret Barbour, Professor Mark Adams

Research Location

Agriculture and Environment - Australian Technology Park

Program Type

PHD

Synopsis

Consideration of theory suggests that increased gm will increase photosynthetic rate without increasing transpirational water loss, resulting in increased A/gs and WUE.  gm has been shown to vary nearly as much as stomatal conductance for a single leaf in response to environmental parameters such as drought.  The interaction between environmental and genetic determinants on gm remain to be explored, and mechanistic understanding of gm is in its infancy. The ease with which gm can be measured using the coupled laser-gas exchange system, under a wide range of environmental conditions, will provide insight into variation in gm and allow development of a mechanistic understanding.

USyd recently purchased a suite of instruments to allow novel measurement of the dynamic exchange of carbon and water between leaves and the atmosphere.  Combined with brand new control-environment growth facilities, and field site at Narrabri, this project will be unique in the application of novel basic understanding to the real world.

Additional Information

This project includes a significant field component and will involve use of technically demanding precision instruments.

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Keywords

Photosynthesis, stomatal conductance, stable carbon isotopes, water-use efficiency, grain yield, mesophyll conductance

Opportunity ID

The opportunity ID for this research opportunity is: 1230

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