An Instrumented Rhizotron to Investigate the Root Growth In Wheat.

There has been much recent interest in modifying root system properties to overcome the effects of soil abiotic stress on crop growth and yield (Lynch 2007; Ghanem et al. 2011). Plant root systems are usually exposed to heterogeneous environmental conditions due to vertical differences in soil moisture and strength. Strong subsurface layers of soil can confine root systems to shallower soil layers, thus limiting water uptake from deeper layers. Even in dry periods when the soil surface has been dried by roots, substantial soil moisture can remain at depth (Whalley et al. 2006; 2008; White and Kirkegaard 2010). Increased depth of root penetration in wheat may therefore confer drought tolerance by allowing roots to access soil water at depth (Li et al. 2010; Lopes and Reynolds, 2010). Genetically altering root distribution between upper and lower soil layers may represent a viable strategy to improve access to water, and a recent study indicated that experimentally manipulating the root distribution within a single cultivar altered shoot growth and physiology (Martin-Vertedor and Dodd, 2011).

             A significant barrier to progress  is the availability of suitable laboratory approaches to study root growth. In this poster we describe a rhizotron system 1.4 m high, 0.5 m wide and 0.08 m deep. This is sufficient size to allow the wheat to be grown maturity and to allow the use of buriable soil moisture and related sensors. We present preliminary experiments and report data from long and short straw wheats as well Rht NILs (near isogenic lines) in a mercia background. We also describe how an irrigation system that allows spatial variation in soil moisture in both vertical and horizontal directions. Data from the soil rhizotron system is compared with data from other model systems.

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Lopes MS, and Reynolds MP. 2010 Partitioning of assimilates to deeper roots is associated with cooler canopies and increased yield under drought in wheat. Functional Plant Biology 37, 147-156.   

Martin Vertedor AI, and Dodd IC. 2011 Root-to-shoot signalling when soil moisture is

heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf ABA concentration. Plant Cell and Environment 34, 1164-1175.

Ghanem ME, Hichri I, Smigocki AC, Albacete A, Fauconnier ML, Diatloff E, Martínez-Andújar C, Lutts S, Dodd IC and Pérez-Alfocea F. 2011 Root-targeted hormonal biotechnology to improve crop stress tolerance. Plant Cell Reports 30, 807-823.

Lynch JP 2007 Roots of the second Green Revolution. Australian Journal of Botany 55, 493-512.

Whalley WR, Clark LJ, Gowing DJG, Cope RE, Lodge RJ and Leeds-Harrison P B 2006 Does soil strength play a role in wheat yield losses caused by soil drying? Plant and Soil. 280, 279-290.

Whalley WR, Watts CW, Gregory AS, Mooney SJ, Clark LJ, Whitmore AP. 2008. Effect of soil drying on the yield of wheat grown on shrinking and non-shrinking soil. Plant and Soil.  306, 237-247.

White RG, and Kirkegaard JA. 2010. The distribution and abundance of wheat roots in a dense, structured subsoil – implications for water uptake Plant, Cell and Environment 33, 133–148