Biology ETDs

Publication Date

7-1-2009

Abstract

Control of stomatal aperture is the primary way plants regulate gas exchange in the short-term, but what triggers stomatal responses to water stress is still debated. Chlorophyll-a fluorescence imaging, local leaf temperature, and gas exchange were measured simultaneously following a cut to primary leaf vein of Helianthus annuus to access the effect of local leaf xylem cavitation on leaf function. The treatment was repeated under 3 different vapor pressure deficit (VPD) conditions. Surprisingly, photosynthesis (A) and stomatal conductance (gs) responded inversely immediately following the treatment, indicating that A was not CO2 limited by stomatal closure. Comparisons of fluorescence images and temperature data showed that while both A and gs responded heterogeneously across the measured leaf area, local responses did not correspond spatially or temporally, suggesting that each was the result of a different mechanism and/or was initiated by a separate signal. Since the stomatal response varied with VPD but A did not, it is likely that only gs was ultimately responding to a hydraulic signal. Both A and gs recovered to near steady state levels by 900s after the cut. These results indicate that stomata respond immediately to a sudden hydraulic perturbation and that hydraulic redundancy in sunflower is sufficient to allow quick recovery to local interruption of vascular system. This experiment also provides evidence of transient de-coupling of A and gs following wounding.

Language

English

Keywords

stomata, electrical potential, heterogeneous behavior, photosynthesis, hydraulic conductance, hydraulic architecture

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Hanson, David

Second Committee Member

Sinsabaugh, Robert

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