Document: DEN-3-30-21

Seasonal pattern and influence of water stress on photosynthesis and 2-methyl-3-buten-2-ol emission from ponderosa pine.

GRAY, D.W.* 1, M.T.LERDAU 1 and A.H.GOLDSTEIN 2

State University of New York, Stony Brook NY 11794-5245 1
University of California, Berkeley 2

Abstract:
Ecophysiological controls, phenological patterns and the influence of water stress on emission of 2-methyl-3-buten-2-ol (MBO) were studied in a ponderosa pine plantation in the central Sierra Nevada Mountains of California. Photosynthesis and MBO emission rates were made using gas exchange techniques and gas chromatography; light, temperature, and CO2-response curves were generated for both processes. Monthly measurements (June-October) of photosynthesis and MBO emission were made on all available needle age classes at both a site experiencing a natural summer drying cycle and a well watered site. MBO emission increased logarithmically with light exactly paralleling the light response of photosynthesis. MBO emission increased exponentially with temperature while photosynthesis declined. MBO emission increased in response to CO2, reaching a maximum at 350 ppm and declining slightly at higher values. Needles began emitting MBO within 2 weeks of the start of needle expansion. Emission of MBO under constant conditions (basal emission rate) declined with needle age. Under constant conditions MBO emission did not vary over the course of the day, but showed a pronounced pattern over the course of the season. The seasonal pattern of basal MBO emission was correlated with seasonal changes in ambient temperature, but was not correlated with seasonal trends in photosynthetic capacity. An identical response of basal MBO emission rate to ambient temperature was seen at both the drought-stressed and well-watered site. We conclude that MBO emission is regulated independently of photosynthesis and postulate that ambient temperature regulates the capacity of a needle to produce MBO.

Keywords: MBO methylbutenol 2-methyl-3-buten-2-ol photosynthesis water stress temperature

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This abstract is being presented at: 3:45 PM in session:
Oral Session #34: Water Relations in Trees.