Abstract Detail

Physiology

Geisler, Mathew [1], Serpe, Marcelo [1].

Stomatal sensitivity to declining leaf water potentials in juvenile plants of Artemisia tridentata ssp. wyomingensis.

Plant species vary in their stomatal sensitivity to decreases in leaf water potential, and this variability affects how plants control transpiration and photosynthesis to survive under drought. Artemisia tridentata is a common shrub in semiarid regions of western North America. This species includes several subspecies, of which A. tridentata ssp. wyomingensis (Wyoming big sagebrush) occupies the most xeric locations. We conducted a greenhouse trial to assess the transpiration and photosynthetic response of 18-months old plants exposed to a gradual and terminal drought. A sigmoid function was used to fit the relationship between leaf water potential and the following physiological parameters: stomatal conductance, transpiration, CO₂ assimilation, and photosystem II operating efficiency (ΦPSII). From this function, we estimated the leaf water potential that caused a 50% reduction (Ψ₅₀) of the parameter values observed in well-watered plants. The greenhouse study was complemented with measurements of leaf water potential and stomatal conductance in plants of the same age that were experiencing their first summer in the field. Under greenhouse conditions, Ψ₅₀ for stomatal conductance was –1.8 (± 0.4) MPa, while 75 and 25% of maximal stomatal conductance occurred at water potentials of -1.2 and -2.9 MPa, respectively. Somewhat lower but not statistically significant values of Ψ₅₀ were recorded for transpiration (-2.3 ± 0.4 MPa) and CO₂ assimilation (-2.47 ± 0.3). Photosystem II operating efficiency (ΦPSII) showed a good correlation with CO₂ assimilation. Yet, the Ψ₅₀ for ΦPSII (-4.5 ± 0.4 MPa) was lower than that for CO₂ assimilation. In the field, the relationship between leaf water potential and stomatal conductance was more variable than in the greenhouse; Ψ₅₀ for stomatal conductance was -3.0 (± 1.5) MPa. From late July to early September, the average midday leaf water potential in the field was -3.4 (± 1.4) MPa; this variability was mainly due to differences between plants rather than the day of measurement. Mortality in these plants was minimal, suggesting that young plants of Wyoming big sagebrush can tolerate water potentials down to at least -5 MPa. Overall, the stomatal responses observed indicate that these plants tend toward the anisohydric side of the isohydric/anisohydric continuum; thus, their stomata are not very sensitive to changes in leaf water potential.

1 - Boise state university, Biological Sciences, 1910 University Drive, Boise, ID, 83725-1515, United States

Keywords:
none specified

Presentation Type: Poster
Session: P3, Physiology Posters
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: P3PS003
Abstract ID:402
Candidate for Awards:None