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Impact of a short-term heat event on C and N relations in shoots vs. roots of the stress-tolerant C4 grass, Andropogon gerardii

Authors
Journal
Journal of Plant Physiology
0176-1617
Publisher
Elsevier
Publication Date
Volume
171
Issue
12
Identifiers
DOI: 10.1016/j.jplph.2014.04.006
Keywords
  • Exudation
  • Heat Wave
  • High Temperature
  • Nutrients
  • Roots

Abstract

Abstract Global warming will increase heat waves, but effects of abrupt heat stress on shoot–root interactions have rarely been studied in heat-tolerant species, and abrupt heat-stress effects on root N uptake and shoot C flux to roots and soil remains uncertain. We investigated effects of a high-temperature event on shoot vs. root growth and function, including transfer of shoot C to roots and soil and uptake and translocation of soil N by roots in the warm-season drought-tolerant C4 prairie grass, Andropogon gerardii. We heated plants in the lab and field (lab=5.5days at daytime of 30+5 or 10°C; field=5days at ambient (up to 32°C daytime) vs. ambient +10°C). Heating had small or no effects on photosynthesis, stomatal conductance, leaf water potential, and shoot mass, but increased root mass and decreased root respiration and exudation per g. 13C-labeling indicated that heating increased transfer of recently-fixed C from shoot to roots and soil (the latter likely via increased fine-root turnover). Heating decreased efficiency of N uptake by roots (uptake/g root), but did not affect total N uptake or the transfer of labeled soil 15N to shoots. Though heating increased soil temperature in the lab, it did not do so in the field (10cm depth); yet results were similar for lab and field. Hence, acute heating affected roots more than shoots in this stress-tolerant species, increasing root mass and C loss to soil, but decreasing function per g root, and some of these effects were likely independent of direct effects from soil heating.

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