Tania Galindo-Castañeda, Kathleen M. Brown, Jonathan P. Lynch


Plant, Cell & Environment, 2018

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Root phenes and phene states that reduce the metabolic cost of soil exploration may improve plant growth under low phosphorus availability. We tested the hypothesis that under low phosphorus, reduced Living Cortical Area (LCA) would increase soil exploration, phosphorus capture, biomass and grain yield. Maize genotypes contrasting in LCA were grown in the field and in greenhouse mesocosms under optimal and suboptimal phosphorus regimes. Percent LCA in nodal roots ranged from 25-67%. Plants with 0.2 mm2 less LCA under low phosphorus had 75% less root segment respiration , and 54% less root phosphorus content, rooted 20 cm deeper, allocated up to four times more roots between 60 - 120 cm depth, had between 20-150% more biomass, 35-40% greater leaf phosphorus content, and 60% greater grain yield compared to plants with high LCA. Low LCA plants had up to 55% less arbuscular mycorrhizal colonization in axial roots, but this decrease was not correlated with biomass or phosphorus content. The LCA components cortical cell file number and cortical cell size were important for biomass and phosphorus content under low phosphorus. These results are consistent with the hypothesis that root phenes that decrease the metabolic cost of soil exploration are adaptive under phosphorus stress.