Growth & Development

Auxin redistribution modifies maize root proliferation

We know that maize roots chase after phosphorus, but how? Xin Wang and colleagues have been investigating what purpose the hormone auxin has in controlling root proliferation. Their work could help better understand how plants work to capture phosphates in the soil.

Plants require phosphorus to grow, and it’s essential for any crop. But it is often unevenly distributed in the soil as phosphates, and plants have to go foraging for it. Roots can take a lot of effort to build, so controlling when to create new roots is an important trait for plants. When a plant hits a phosphate-rich spot of soil, then creating new roots in the area is a very effective way of grabbing it.

Wang and colleagues took a closer look at the roots. They asked if a patchy phosphate supply influenced root distribution by changing the distribution of auxin in the plant. They grew plants in controlled conditions so that some roots would have access to higher concentrations of phosphates than other roots. Other plants had uniform access to either high or low levels of phosphates

Sure enough, they found that the plants put more effort into growing roots that had access to the high phosphate compartment in their experiment. They also found that the proliferation of lateral roots was accompanied by an enhanced auxin response in the apical meristem and vascular tissues at the root tip. Further, inhibiting the auxin in a plant also inhibited preferential root growth.

Graph showing the effect of phosphate on root growth
Effect of homogeneous and heterogeneous Pi supply on plant growth and P status. Source: Wang et al. 2020.

“The shoots of the plants receiving a heterogeneous HP supply achieved a similar biomass and P content to plants receiving a homogeneous HP supply,” write the authors, “despite having access to only half the Pi supply. These results suggest that, in comparison with a homogeneous HP supply, roots receiving a heterogeneous Pi supply had enhanced P acquisition efficiency (i.e. Pi acquisition per unit root length), which contributed to P uptake and biomass production.”

Wang and colleagues conclude, “…manipulation of auxin signalling could be a means to improve root system architecture and increase Pi efficiency of crops in soils with spatially heterogeneous Pi supply.”