Plant-soil interactions: the impact of plant water use efficiency on root architecture and soil structure

Improving the worlds’ agricultural productivity is paramount for the eradication of hunger, a key sustainable development goal. As agricultural production across the world currently accounts for more than 70% of global freshwater withdrawals. The increased agricultural production required to feed an ever-expanding global population is set to put serious strain on the worlds’ already limited freshwater resources. Development of plants with improved water use efficiency to maximise on the erratic global freshwater supply has largely been suggested as a possible strategy to bring about significantly increased crop production per unit of water available. The effectiveness of the utility of such plants, however, may come at a cost to soil health, which would ultimately lead to reduced sustainability of crop production. In cognisance of this, this study aimed at investigating how genetically altering plant water use efficiency (WUE) may have a bearing on a plant's root system architecture (RSA) and consequently soil structure. This research was focused on the water use efficient mutants of three different plant species, namely Thale Cress (Arabidopsis Thaliana), common bread wheat (Triticum aestivum) and rice (Oryza Sativa). I investigated how genetically altering WUE in these different plants affects their RSA using both invasive (Root washing) and non-invasive (X-Ray and Neutron computed tomography) methods to unravel their RSA in 2 and 3D. Subsequently, changes in soil structure were inferred using aggregate stability testing. I did not find conclusive evidence suggesting that genetically altering WUE in wheat and Arabidopsis had an effect on their RSA and soil structural stabilisation. On the other hand, I found reasonable evidence suggesting that rice plants with genetically enhanced WUE had reductions in their RSA development. There was also evidence suggesting that in wetland grown rice, the aggregate stability of at least one aggregate size fraction (1-2mm) was significantly reduced.