2.2 Sampling and sample processing
After 7 weeks of growth, we harvested five microcosms per plant
diversity level in the PPI experiment and five microcosms per soil
legacy level-planted species combination in the PSI experiment
(Appendix Table A1 & A2 ). We separated the shoot and root
biomass of one randomly selected plant individual per species and
microcosm by cutting the plants with scissors. We washed the roots twice
under tap water to remove soil particles, and then dried the samples
with paper towels. This process took roughly 30 s. All shoot and root
samples were then immediately stored in paper bags on dry ice to stop
further metabolism. This resulted in a total of 20 shoot and 20 root
samples per species and experiment.
After one additional week of herbivory (see above), we harvested the
remaining five microcosms per diversity level in the PPI experiment and
five microcosms per soil legacy level-planted species combination in the
PSI experiment (Appendix Table A1 & A2 ). We sampled the foliar
tissue of one randomly selected control and one randomly selected
induced plant individual per species and microcosm by cutting the plants
ca. 1 cm above the ground. All samples were then immediately stored in
paper bags on dry ice. This resulted in a total of 20 control and 20
induced samples per species and experiment.
In the lab, all samples were stored in a -80°C freezer, and
subsequently, freeze-dried (LABCONCO FreeZone Plus 12 Liter, Kansas
City, USA) for 72 h. Dried samples were stored in zip-lock bags filled
with silica gel at room temperature until we had ground each sample to a
fine homogenous powder using a ball mill (Retsch mixer mill MM 400,
Haan, Germany).