Root cortical senescence decreases root respiration, nutrient content and radial water and nutrient transport in barley

• Published in: Plant, cell and environment Vol. 40; no. 8; pp. 1392 - 1408
• Main Authors: Schneider, Hannah M., Wojciechowski, Tobias, Postma, Johannes A., Brown, Kathleen M., Lücke, Andreas, Zeisler, Viktoria, Schreiber, Lukas, Lynch, Jonathan P.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.08.2017
• Subjects: Adaptiveness; Aliphatic compounds; Barley; Biological Transport; carbon; Cell Respiration; cortex; endodermis; Genetic diversity; genetic variation; Germplasm; Hordeum - cytology; Hordeum - metabolism; Hordeum vulgare; landraces; Lipids; Nitrates; Nitrogen; Nitrogen - metabolism; nitrogen content; Nutrient content; Nutrient transport; Phosphorus; Phosphorus - metabolism; Plant growth; Plant Roots - cytology; Plant Roots - growth & development; Plant tissues; radial transport; Resource allocation; Respiration; root growth; roots; Rye; Segments; Senescence; Soil; Soils; stele; suberin; suberization; Transport; Triticale; Water - metabolism; Wheat; Hordeum vulgare; radial transport; suberin
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12933

The functional implications of root cortical senescence (RCS) are poorly understood. We tested the hypotheses that RCS in barley (1) reduces the respiration and nutrient content of root tissue; (2) decreases radial water and nutrient transport; and (3) is accompanied by increased suberization to protect the stele. Genetic variation for RCS exists between modern germplasm and landraces. Nitrogen and phosphorus deficiency increased the rate of RCS. Maximal RCS, defined as the disappearance of the entire root cortex, reduced root nitrogen content by 66%, phosphorus content by 63% and respiration by 87% compared with root segments with no RCS. Roots with maximal RCS had 90, 92 and 84% less radial water, nitrate and phosphorus transport, respectively, compared with segments with no RCS. The onset of RCS coincided with 30% greater aliphatic suberin in the endodermis. These results support the hypothesis that RCS reduces root carbon and nutrient costs and may therefore have adaptive significance for soil resource acquisition. By reducing root respiration and nutrient content, RCS could permit greater root growth, soil resource acquisition and resource allocation to other plant processes. RCS merits investigation as a trait for improving the performance of barley, wheat, triticale and rye under edaphic stress. Root cortical senescence (RCS) is a poorly understood phenomenon with functional implications for plant performance. RCS reduced root respiration and nutrient content, decreased radial water and nutrient transport and was accompanied by increased suberization of the endodermis. RCS may have adaptive significance for soil resource acquisition by reducing root carbon and nutrient costs thereby permitting greater root growth, soil resource acquisition and resource allocation to other plant processes.