Measures of leaf-level water-use efficiency in drought stressed endophyte infected and non-infected tall fescue grasses

Debbie Swarthout, Emily Harper, Stephanie Judd, David Gonthier, Rebekah Shyne, Timothy Stowe, Thomas Bultman

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Neotyphodium coenophialum [Morgan-Jones and Gams], grows in the above-ground parts of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]. It is an asexual fungus that is transmitted through seed of its host plant. This grass/endophyte association is enhanced by the protection of the host from herbivory and improved drought stress. We investigated how a decline in leaf-level stomatal conductance impacts the instantaneous water-use efficiency (WUE), in endophyte-infected (E+) versus non-infected (E-) Kentucky-31 tall fescue grasses grown in a controlled environmental chamber over a 10-week period. Grasses were cut at 6 weeks after germination and allowed to regrow under high and low soil moisture availability. One week after cutting, soil moisture was allowed to decline in the low water treatment for 2 weeks until severe stress was demonstrated through a decline in stomatal conductance to less than 100 mmol m-2 s-1. We found no differences in WUE between E+ and E- plants when water was not limiting while higher WUE was exhibited in E+ plants relative to E- plants under severe drought stress. The E- plants showed an 18-fold reduction in mean WUE and a 70-fold reduction in photosynthesis under drought stress, while there was no change in WUE and only a fourfold decline in photosynthesis between well-watered and drought stressed E+ plants at 21 days. While there were no differences in the rates of transpiration between E+ and E- plants under severe drought stress, differences in WUE can be attributed mainly to higher photosynthetic rates of E+ than E- plants. The difference in photosynthetic rates between E+ and E- plants under drought conditions could not be explained by differences in stomatal conductance and Rubisco (EC activities.

Original languageEnglish
Pages (from-to)88-93
Number of pages6
JournalEnvironmental and Experimental Botany
Issue number1
StatePublished - Apr 2009

Bibliographical note

Funding Information:
H. Fribourg, the University of Tennessee, kindly supplied the Kentucky-31 tall fescue seeds. This study was funded by the NSF-CRUI grant (#0330840) and NSF-MRI grant (#0319938). We are grateful to Chris Schardl (University of Kentucky) for providing us with the fungal antibody.


  • Conductance
  • Endophyte
  • Photosynthesis
  • Tall fescue
  • Water-use efficiency

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Agronomy and Crop Science
  • Plant Science


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