Thesis: Linking restriction of nitrogen transporter systems to nitrate-influx restraint in the high phosphorus-use-efficient Hakea prostrata (Proteaceae)
Phosphorus (P), an essential plant nutrient, is in extremely low supply in soils of south-western Australia. While crop species require heavy P fertiliser use to achieve maximum yield in Australia, native Australian plants are excellently adapted and thrive with high photosynthetic rates. The traits of these native plants are of considerable interest for reducing the need for P fertiliser in cropping systems. Such development could occur by traditional breeding or genetic modification. However, research must firstly be undertaken into the P-efficient traits and their associated impacts on plants.
One impact is the linking of high P-efficiency with nitrogen (N), which is another essential plant nutrient. Nitrogen is greedily taken up by most plants to store for later use because of the fluctuating supply in soil. The main form taken up is usually an ion called nitrate. However, native south-west Australian plants may have a different strategy. One such native plant, harsh hakea (Hakea prostrata) in the Proteaceae family, appears to only take up a small, set amount of nitrate regardless of the amount given to it. This apparent restriction of nitrate uptake has been termed nitrate restraint. Nitrate restraint may be a crucial trait because it complements the important P-saving strategy of low protein production which is exhibited harsh hakea. Because protein production is a major use for N and P in plants, low protein production means less N is needed by harsh hakea. Hence, the plant potentially saves energy by restricting the uptake and assimilation of unneeded N. In my PhD, I am researching nitrate restraint in harsh hakea to determine the following: 1) Is nitrate restraint an adaptation to complement P-saving strategies of native plants or is N still taken up from other sources? 2) What are the physiological/genetic mechanisms for nitrate restraint in harsh hakea? 3) Is nitrate restraint (if discovered in other Australian species) due to the same mechanisms?
Why my research is important
The main goal of studying P-efficient traits of native south-west Australian plants is to reduce P fertiliser use for the future. Not only is P fertiliser incredibly expensive for farmers, but its use degrades natural waterways and the major source from mines is non-renewable and mainly from politically unstable countries. The demand for P fertiliser is also increasing as the human population continues to grow. Crops developed with even some of the P-saving traits from native Australian plants would greatly reduce the amount of P fertiliser needed worldwide, solving these impending issues. In addition, most of the current knowledge on P and N relations has been done on crop species which are only distantly related to native Australian plants. Hence, my research will advance knowledge on the diversity of P and N relations in plants along with working towards a secure future for global food production.