Watching plants drink

Water is essential to life, human health, food production and economic activity. The growth in global population and manufacturing, combined with the impact of climate change, are placing unsustainable demands on water resources. The agricultural sector is the major user of freshwater resources, accounting for >70% of withdrawals globally, and >90% in less-developed countries. By 2050, agriculture must produce 60% more food globally and 100% more in developing countries. The current rate of agricultural water demand is clearly unsustainable. Inefficient water use for crop and food production has depleted aquifers, reduced river flows, and salinised >20% of global irrigated land (FAO, 2011). The 2015 UN World Water Development Report noted that ‘the single most important avenue for managing water demand in agriculture is through increasing agricultural productivity,’ flagging the importance of the choice of genetic material to produce ‘more crop per drop’ of water applied. 

However, such developments require fundamental new knowledge. For example, researchers still need to discover how plants take up water to engineer more water-efficient crops. Despite decades of research, key questions about water uptake in plants remain to be resolved – such as where, when and how do roots take up water? The current inability to non-invasively monitor water transport in root tissues has been a key stumbling block to answer these questions. Engineers at the University of Nottingham have recently developed a non-invasive technique to image water dynamics in living tissues. A team of Plant Scientists and Engineers will use this technique to directly image and quantify water transport in root tissues. Employing this innovative technique, the inter-disciplinary team will address where, when and how do roots take up water.

Schematic drawing of cells involved in water transport from the outside of the root (epidermis) to the central vessels conducting water to the shoot (xylem). Water uptake in plant roots is either through cell walls (pink arrow) and controlled by impermeable barriers (Casparian strip) or by cell-to-cell transport (blue arrow) controlled by pores (plasmodesmata). [The detailed diagram of root cells is a modification of Into the stele by Kelvin13 / CC-BY-SA-3.0]

Where? We will determine the site(s) of water uptake in roots addressing, for example, whether water uptake is limited to growing root tips or does it take place over a much wider area of the root system including mature root tissues? 

How? The next objective will determine whether water uptake in different root zones is controlled by impermeable barriers (such as the Casparian Strip), specialised water channels or pores between cells termed plasmodesmata (see figure above), by exploiting a panel of Arabidopsis thaliana mutants engineered to disrupt these individual components. 

When? Mature root tissues have been reported to become permeable depending on external water availability from soil. This final objective will address whether the root Casparian Strip becomes permeable when water is available in the soil and impermeable under abiotic stress conditions. 

This new technique will deliver important new mechanistic insights into where, how and when water uptake is regulated in roots, by direct measurement of water uptake. The project will exploit an array of unique plant genetic resources developed in our and collaborators labs at Nottingham. The biological insights resulting from this interdisciplinary study will provide invaluable information to aid efforts to re-engineer root tissues and help produce ‘more crop per drop' (Davies & Bennett, 2015, Nature Plants 1:15118). 

Professor Malcolm Bennett
University of Nottingham
Research Project Grant

Co-investigators: Dr Kevin Webb, Dr Darren M Wells