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Abstract

Scots pine populations contain individuals with widely differing amounts and
composition of monoterpenes and exist as one of two chemotypes: with or without Δ3-
carene. We investigated the significance for ecological studies of two types of variation in
monoterpenes: (1) the inherent variability in the concentration of monoterpenes or their
relative amounts in needles of seedlings, saplings, and mature trees; and (2) phenological
variation in developing needles. The relative composition of needle monoterpenes in 5-
year-old saplings changed during the needle development period until the final composition
was reached upon needle maturity. Changes in composition depended on chemotype.
Needles of the “no-Δ3-carene” chemotype had higher absolute concentrations of !-pinene,
"-pinene, camphene, and total monoterpenes than “Δ3-carene” chemotype. For the “Δ3-
carene” chemotype, the relative concentration of Δ3-carene during the needle growing
season and immediately after emergence of seedlings was higher compared to that reached
at needle maturity. Repeated removal of single needles (at weekly intervals during growth)
from 5-year-old saplings did not influence the composition of monoterpenes. Within a
natural Scots pine dominated woodland, 18% of mature Scots pines (N=574) belonged to
the “no-Δ3-carene” chemotype. Chemotypic variation within populations means that the
statistical power with which differences in monoterpene concentrations can be detected is
lower when sampling from the whole population compared to sampling within chemotypes.
Reduction of this background variation and accounting for chiral variation if present, would
significantly aid efficiency, interpretation, and understanding of processes in chemical and
ecological research. One method for achieving this is the screening of plants for chemotypes
before the establishment of experiments or field sampling regimes.We present a summary of
suitable analytical methods for needle tissue that facilitates this prior screening.

Item Type:	Article
Authors/Creators:	Thoss, V and O'Reilly-Wapstra, JM and Iason, GR
Keywords:	Absolute concentration - α-pinene - Camphene - β-pinene - Δ3-carene - Chemotypes - Relative composition - Seasonal variation
Journal or Publication Title:	Journal of Chemical Ecology
Publisher:	Springer New York LLC
ISSN:	0098-0331
DOI / ID Number:	10.1007/s10886-006-9244-3
Additional Information:	The original publication is available at www.springerlink.com
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