Document: MAR-3-30-16

Effects of elevated CO₂ concentrations during growth on isoprene emissions from velvet beans (Mucuna sp.).

POTOSNAK, M.J.* and K.L.GRIFFIN

Columbia University, Palisades, NY 10025 USA ¹

Abstract:
Velvet beans (Mucuna sp.) were grown from seed in four Conviron chambers during two separate experiments to explore the effects of acclimation to elevated CO₂ on basal rates of isoprene emission. In each experiment, plants were grown for 2 months under controlled conditions of light, temperature, relative humidity and CO₂, and then isoprene flux measurements at standard conditions and leaf biochemistry data were collected over four days. The first experiment manipulated CO₂ (37/73 Pa) and relative humidity (40/70 %) in a two by two factorial design. The velvet beans grown at 73 Pa CO₂ had significantly (~25%) lower emissions than the ambient CO₂ plants, but the relative humidity treatment had no significant effect. In this experiment, isoprene emissions were well correlated to leaf nitrogen content (r² = 0.80), raising the possibility that isoprene emissions were suppressed due to nutrient limitations caused by increased biomass. During the second experiment, again CO₂ (37/73 Pa) was varied, but instead of relative humidity, daytime temperature (26/34 C) was chosen as the second factor. Unfortunately due to a chamber malfunction, the 37 Pa/24 C chamber was lost, but a comparison of the two 34 C chambers again showed that elevated CO₂ concentrations suppressed isoprene emissions. Nutrient limitation does not explain this result, since fertilization was increased and there was no correlation between nitrogen content and isoprene emissions. Two measures of leaf biochemistry provided additional insight. Rubisco activity was well correlated to isoprene emissions within the 73 Pa/24 C treatment, but there was no correlation for the 37 and 73 Pa/32 C treatments. On the other hand, glucose content was well correlated to isoprene emissions for these two treatments, but not for the 73 Pa/24 C treatment. In addition to nitrogen content and glucose, sucrose, chlorophyll A, chlorophyll B, total protein, and Vcmax and Jmax (from ACi curves) data were collected during at least one of the experiments, and no single correlate was found that could predict basal rates of emissions across the different treatments.

Keywords: isoprene elevated carbon dioxide mucuna hydrocarbons

This abstract is being presented at: 3:30 PM in session:
Oral Session #30: Effects of Elevated Carbon Dioxide.