PARENT SESSION
Poster Session # 15: Plant Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Modeling leaf conductance of Acer rubrum L. ecotypes from contrasting hydrological habitats: Integrating biochemical and hydraulic signaling.

Bauerle, William^*,1, Bauerle, Taryn², ¹ Clemson University, Clemson, SC² Penn State University, University Park, PA

ABSTRACT- Recent evidence in an herbaceous system indicates that chemical and hydraulic stomata controls are a function of the combined responses of both above and below ground environments. To date, nearly all woody plant models used to study atmospheric and subterranean water stress treat the above and below ground environments separately. In woody plant systems, however, the significance of the link between chemical and hydraulic control on regulating stomatal conductance (g_s) is still unclear. To examine the effects of atmospheric and subterranean water stress on leaf chemical and hydraulic signals, we modeled stomatal water loss in response to gas exchange function. We test the hypothesis that chemical, hydraulic, and aerial g_s controls act sequentially. In an attempt to quantify the combined control of g_s in Acer rubrum L., a woody species known to radiate into contrasting hydrologic extremes, two existing woody plant data sets were used. The presence of intraspecific variation between wet and dry site red maple populations in physiological response to atmospheric vapour pressure deficits and soil water stress in a previous study provided the impetus to compare combined g_s control models to more common empirical aerial environment models in a woody plant system. Coupling leaf water potential (_L) and bulk leaf abscisic acid (ABA_L) in a combined model of stomatal response to leaf and soil environment improved the g _s prediction over common aerial empirical models. The results support the hypothesis that ABA_L and _L may act sequentially and, based on the results, ecotypic variation in stomatal responsiveness to air humidity is likely mediated by ABA accumulation in leaf tissue. The results also suggest that growth environment can influence the g_s response. Based on the findings, more research into physiological integration of biochemical and hydraulic signaling is warranted.

Key words: stomatal conductance, modeling, gas exchange