Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Aug;174(4):2333-2347.
doi: 10.1104/pp.17.00648. Epub 2017 Jun 30.

Root Cortical Senescence Improves Growth under Suboptimal Availability of N, P, and K

Hannah M Schneider  1 , Johannes A Postma  1 , Tobias Wojciechowski  1 , Christian Kuppe  1 , Jonathan P Lynch  2
Affiliations

Root Cortical Senescence Improves Growth under Suboptimal Availability of N, P, and K

Hannah M Schneider et al. Plant Physiol. 2017 Aug.

Abstract

Root cortical senescence (RCS) in Triticeae reduces nutrient uptake, nutrient content, respiration, and radial hydraulic conductance of root tissue. We used the functional-structural model SimRoot to evaluate the functional implications of RCS in barley (Hordeum vulgare) under suboptimal nitrate, phosphorus, and potassium availability. The utility of RCS was evaluated using sensitivity analyses in contrasting nutrient regimes. At flowering (80 d), RCS increased simulated plant growth by up to 52%, 73%, and 41% in nitrate-, phosphorus-, and potassium-limiting conditions, respectively. Plants with RCS had reduced nutrient requirement of root tissue for optimal plant growth, reduced total cumulative cortical respiration, and increased total carbon reserves. Nutrient reallocation during RCS had a greater effect on simulated plant growth than reduced respiration or nutrient uptake. Under low nutrient availability, RCS had greater benefit in plants with fewer tillers. RCS had greater benefit in phenotypes with fewer lateral roots at low nitrate availability, but the opposite was true in low phosphorus or potassium availability. Additionally, RCS was quantified in field-grown barley in different nitrogen regimes. Field and virtual soil coring simulation results demonstrated that living cortical volume per root length (an indicator of RCS) decreased with depth in younger plants, while roots of older plants had very little living cortical volume per root length. RCS may be an adaptive trait for nutrient acquisition by reallocating nutrients from senescing tissue and secondarily by reducing root respiration. These simulated results suggest that RCS merits investigation as a breeding target for enhanced soil resource acquisition and edaphic stress tolerance.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Spatial map of RCS formation in simulated barley root systems at 80 DAG. Colors indicate RCS formation as a percentage of the cortical area senesced. Roots have been dilated (approximately 2×) for enhanced visualization and do not indicate true root diameter.
Figure 2.
Figure 2.
Utility of RCS formation under varying availability of nitrogen, phosphorus, and potassium dissolved in solution at the start of the simulation. Total phosphorus and potassium concentrations are greater due to the buffering capacity (P, 400; and K, 10). On the y axis, the utility of RCS is expressed as a percentage increase in plant dry weight (DW) at 80 DAG. On the secondary y axis, dry shoot biomass is presented for a plant with no RCS. Relative shoot dry biomass was calculated as 100 × (XRCS − XnoRCS)/XnoRCS. Different lines show the utility for different functions (allocation, respiration, and uptake) of RCS. Error bars represent se for four repeated runs. Simulated stochasticity in root growth rates, directions, and branching density causes variation.
Figure 3.
Figure 3.
RNR (y axis; µmol plant−1) as affected by RCS and nutrient availability. RCS reduces RNR of the cortex; however, RNR for the whole root system depends on the size and age distribution of the root system. Different bars show the utility for different functions of RCS under suboptimal nitrogen, phosphorus, and potassium availability. Error bars represent se (see Fig. 2 for explanation). Different letters within the same graph represent significant differences within that graph as determined by Tukey’s test (P < 0.05). Intermediate and optimal nutrient availability levels showed the same pattern and are depicted in Supplemental Figure S5.
Figure 4.
Figure 4.
Effects of the RCS respiration function on cumulative root respiration in optimal and suboptimal nitrogen, phosphorus, and potassium availability. Cumulative respiration is cortical respiration of the entire root system at 80 DAG. Different bar groups show the utility for different functions of RCS at two levels of nutrient availability (low availability and optimal availability). Cortex Respiration, RCS, Cumulative respiration of the root system cortex after the formation of RCS; Cortex Respiration, no RCS, simulated cumulative respiration of the root system cortex if no RCS has developed. Error bars represent se (see Fig. 2 for explanation). Different letters within the same graph represent significant differences within that graph as determined by Tukey’s test (P < 0.05).
Figure 5.
Figure 5.
Effects of the RCS respiration function on plant carbon reserves. Different bars show the utility for different functions of RCS under varying nitrogen, phosphorus, and potassium availability. The total amount of carbon reserves in the shoot at 80 DAG is represented on the x axis. Error bars represent se (see Fig. 2 for explanation). Different letters within the same graph represent significant differences within that graph as determined by Tukey’s test (P < 0.05).
Figure 6.
Figure 6.
Effects of RCS on nitrogen, phosphorus, and potassium uptake in fertile soil. Uptake is the total nutrient uptake at 80 DAG by axial or lateral roots. Different bars show the utility for different functions of RCS. Error bars represent se (see Fig. 2 for explanation). Different letters within the same graph represent significant differences within that graph as determined by Tukey’s test (P < 0.05). Uptake data for suboptimal nutrient availability are depicted in Supplemental Figure S6.
Figure 7.
Figure 7.
Interaction of RCS and tiller number under different availabilities of nitrogen, phosphorus, and potassium. Error bars represent se (see Fig. 2 for explanation). Dry shoot biomass is the total dry shoot biomass at 80 DAG. Note that in suboptimal phosphorus and potassium availability, plants with many tillers formed three tillers (with the potential to form four tillers) due to stress conditions.
Figure 8.
Figure 8.
Interaction of RCS and lateral branching densities under varying availability of nitrogen, phosphorus, and potassium. Error bars represent se (see Fig. 2 for explanation). Dry shoot biomass is the total dry shoot biomass at 80 DAG.
Figure 9.
Figure 9.
Comparison of RCS progression in simulation (A and B) and field (C and D) studies for roots with a thick or thin stele. For field studies, points represent averages of two cores per plot in two replications for four genotypes per treatment. For simulation studies, points represent averages of four replications per treatment. Error bars represent se.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Alm DM, Cavelier J, Nobel PS (1992) A finite-element model of radial and axial conductivities for individual roots: development and validation for two desert succulents. Ann Bot (Lond) 69: 87–92
    1. Baxter I, Hosmani PS, Rus A, Lahner B, Borevitz JO, Muthukumar B, Mickelbart MV, Schreiber L, Franke RB, Salt DE (2009) Root suberin forms an extracellular barrier that affects water relations and mineral nutrition in Arabidopsis. PLoS Genet 5: e1000492. - PMC - PubMed
    1. Bingham IJ. (2007) Quantifying the presence and absence of turgor for the spatial characterization of cortical senescence in roots of Triticum aestivum (Poaceae). Am J Bot 94: 2054–2058 - PubMed
    1. Blum A. (1998) Improving wheat grain filling under stress by stem reserve mobilisation. Euphytica 1000: 77–83
    1. Bonser AM, Lynch J, Snapp S (1996) Effect of phosphorus deficiency on growth angle of basal roots in Phaseolus vulgaris. New Phytol 132: 281–288 - PubMed

LinkOut - more resources

-