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Abstract Detail


Environmental Physiology

Swarthout, Debbie, J [1], Harper, Emily [2], Judd, Stephanie [2].

Water-use efficiency in endophyte infected Lolium arundinaceum grasses.

Neotyphodium coenophialum (Ascomycota: Claviciptaceae) grows intercellularly in above-ground parts of C3 grasses. It is an asexual fungus that is transmitted through seed of its host plants. This grass/endophyte association is based on the protection of the host from herbivory and improved drought stress. We performed experiments to determine if a change in stomatal conductance impacts the instantaneous water-use efficiency (WUE),in endophyte-infected (E+) versus uninfected (E-) Lolium arundinaceum grasses grown in controlled environmental chambers over 10-week periods. Grasses were cut at 6 weeks after germination and allowed to regrow under high and low soil moisture availability. Soil moisture was allowed to decline after seven weeks in the low water treatment until severe stress was demonstrated. We found no difference in WUE among E+ and E- plants when water was not limiting. Uninfected plants showed a significant decline in WUE and an increase in ratios of internal to external leaf CO2 partial pressure (pi,/pa) when stomatal conductance decreased under severe drought stress. WUE and pi/pa of E+ plants remained unchanged across a wide range of stomatal conductances. The different responses in water-use efficiency are attributed mainly to a more rapid decline in photosynthesis in E- grasses as severe moisture stress was imposed, whereas E+ plants maintained a more gradual decline in photosynthesis under severe water stress. Leaf Rubisco concentrations were similar in infected and uninfected plants when stomatal conductance declined under severe stress but the activated state of Rubsico was significantly higher in infected versus uninfected plants. The results suggest less damage to the photosynthetic machinery under drought conditions in plants with the fungus relative to plants without the fungus.


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1 - Hope College, Biology, 35E 12th Street, Holland, MI, 49423, USA
2 - Hope College, Biology

Keywords:
stomata
water-use efficiency.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P01009
Abstract ID:286


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