JONES, CLAYTON A. Dept. of Botany and Range Science, Brigham Young University, Provo, UT 84604. - Isotope ratio mass spectroscopy: a powerful tool for analyzing the respective contributions of environment and inheritance in plant growth.
Artemisia tridentata Nutt. ssp. tridentata, and ssp.
vaseyana, along with natural hybrids of the two, are found in
Salt Creek Canyon, near Nephi, Utah, USA. The two subspecies are
separated by 1.1 km along the transect, and 85 m in elevation. Natural
hybrids of the two occur on the same hill between the two parent
populations. In 1993 seedlings from five populations along the
transect were planted in three gardens. The upper, middle, and lower
gardens allowed the five populations to grow in three different
environments. Plant tissue was collected in triplicate from all five
populations in each of the three gardens on 06 Nov. 1999. 5 mg (dry
weight) of plant tissue were then combusted with Cu(II)O wireform, and
Cu granular at 800C. CO2 from the combustion of the plant
tissue was then extracted using cryogenic distillation methods. The
CO2 was later analyzed in a mass spectrometer to measure the ratio of
13C/12C. This isotopic ratio yields a quantitative measurement of
stress in the cumulative growth of the plant tissue. As stresses
increase fractionation also increases and the ratio compared to a
standard becomes more negative. The results of this analysis showed
that, on average, stress/fractionation were highest in the upper
garden and lowest in the lower garden. The environmental contribution
to plant growth is clearly evidenced by the segregation of isotopic
ratios between the gardens. The contribution of inheritance is also
evident in the isotopic data. Stress/fractionation varies positively
with the distance between the source location and the garden location.
In addition to this variance, the hybrids exhibit lower levels of
stress/fractionation in distant gardens than the parent populations.
Mass spectroscopy is a powerful tool in looking at the contributions
of both environment and inheritance in plant growth.
Key words: Artemisia tridentata, Carbon, mass spectroscopy, stable isotopes