ARS | Publication request: Determination of Russian Thistle Epicuticular Wax Density and Composition in Response to Water Stress.

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 11, 2008
Publication Date: September 1, 2008
Citation: Kuehl, L., Burke, I.C., Young, F.L. 2008. Determination of Russian Thistle Epicuticular Wax Density and Composition in Response to Water Stress. Western Society of Weed Science Meeting Proceedings.

Technical Abstract: Russian thistle is a prominent broadleaf weed in the low rainfall zone of the inland Pacific Northwest. Herbicides, including glyphosate, are the most desirable form of weed control. The epicuticular wax layer is a major barrier to herbicide penetration and its characteristics may be affected by drought. An experiment consisting of two separate studies repeated in time was conducted to examine the effects of drought on the epicuticular wax composition of Russian thistle. Three months after germination half of the Russian thistle seedlings in the experiment were subjected to drought conditions. The remaining plants were watered regularly. To impose the drought condition, the incipient wilting point for each plant was identified by withholding water and recording the weight of the system (plant, pot, and soil). Once the plants reached their incipient wilting point they were held there for 25 days by adding 10% of the total water back into the system. Above ground biomass was harvested and total above ground area was recorded. Epicuticular wax was extracted, dried and derivatized for measurement, and then analyzed using a GC-MS. Drought stress did not significantly affect leaf wax density (p = 0.8725) or total wax mass per plant (p = 0.2159), but it did decrease total leaf area per plant (p = 0.0102). No differences were observed between the epicuticular wax composition of drought-stressed and non-drought stressed plants. The epicuticular wax of Russian thistle was primarily composed of pentacosane, heptacosane, and nonacosane, although several primary components were not identifiable.