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.

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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, and the researchers, from the University of Nottingham, believe the added knowledge could lead to development of higher yielding crop plants. 

Using an advanced form of X-ray imaging and operating as part of an international project, the Nottingham team 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.

Professor Malcolm Bennett, from The University of Nottingham's School Of Biosciences, who led the UK team explained, "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."

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. However, little is known about the sense that allows plants to grow in this way.

Nottingham Professor Sacha Mooney 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."