Scientists have discovered how the presence of even small amounts of water can influence the structure of plant roots in soil, a finding that opens up new possibilities to improve water and nutrient foraging for important food crops.
Significant improvements in crop yields are urgently required to meet the 50% increase in world population by 2050. The degree of root branching determines the efficiency of water uptake and acquisition of nutrients in crops. Understanding the regulation of root branching is therefore of vital importance.
Using an advanced form of X-ray imaging BBSRC-funded researchers from The University of Nottingham, working with several international groups including colleagues in the USA, have discovered that root branching is profoundly influenced by the distribution of water in soil. An ability to precisely determine where water is in soil, which is different from a touch-reaction, affects the positioning of new lateral roots. Lateral roots (LR) form on the side of the main root in contact with water, but rarely on the dry side.
The researchers have called this novel process "hydropatterning" and showed that it is common to the experimental model species Arabidopsis as well as the important food crops maize and rice. Their results are published today in the journal Proceedings of the National Academy of Sciences (PNAS).
Professor Malcolm Bennett, from The University Of Nottingham's School Of Biosciences, who led the UK team said: "We have discovered that plant roots can sense small differences in water availability across their diameter. Root branching is a target of hydropatterning, with lateral roots only forming on the side of the main root contacting water in soil. Identifying the genes and signals that control this process opens up new possibilities to improve water and nutrient foraging in crops."
Professor Sacha Mooney, also from The University Of Nottingham's School of Biosciences, added: "Research in this area has traditionally been hampered by the opacity of soil preventing us actually visualising root behaviour in situ and in three dimensions. This is an excellent example of how the latest imaging technologies such as X-ray micro Computed Tomography can help to provide new insights into important biological mechanisms."
The study also showed that a plant hormone called auxin was heavily involved in the hydropatterning process – higher water availability induced plants to produce the hormone, which controls hydropatterning in the roots.
The work was a multidisciplinary collaboration between soil, computer and plant scientists at The University of Nottingham and a plant research group based at the Carnegie Institution for Science in Stanford, California.
In addition to BBSRC support the team received funding from the European Research Council (ERC), Royal Society, Wolfson Charitable Foundation, Distinguished Scientist Fellowship Program (DSFP) at King Saud University, Carnegie Institution for Science, the National Research Foundation of Singapore and a National Science Foundation Graduate Research Fellowship.
The paper "Plant roots use a patterning mechanism to position lateral root branches toward available water" is published in Proceedings of the National Academy of Sciences (PNAS) and will be available at: http://www.pnas.org/cgi/doi/10.1073/pnas.1400966111.
The research team included scientists from the University of Nottingham, Carnegie Institute for Science, National University of Singapore, Stanford University, Universitat Politécnica de Valéncia, University of Lyon and King Saud University, Saudia Arabia.