Synergistic effects of canopy chemistry and autogenic soil biota on a global invader

Soil biota have strong effects on plants, but we have a poor understanding of how plant chemistry might modify these effects. We examined the effect of soil biota associated with an exotic invasive tree, Prosopis juliflora, vs. that associated with native species, from seven sites across India on conspecifics and two other plant species. We then measured changes in species-specific soil biota effects (identified as plant-soil feedbacks, PSFs) when leaf leachate from P. juliflora or from native plant species was added to soil containing respective live and sterile soil inoculum.
We quantified the amino acid L-tryptophan from leaf leachate of P. juliflora, Leucaena leucocephala (another invader), and two native species. We also tested effects of P. juliflora or native species soil inoculum amendment of tryptophan on P. juliflora, P. cineraria, and L. leucocephala across seven sites. We then quantified the microbially metabolized derivatives of tryptophan, phytohormone indole-3-acetic acid..., Experiment 1: Seedlings were harvested and total biomass was recorded following 56 days of growth after oven drying for 48 h at 60°C.
Experiment 2: Seedlings were harvested and total biomass was recorded following 90 days of growth after oven drying for 48 h at 60°C.
Experiment 3: Leaves of Prosopis juliflora, Leucaena leucocephala, Prosopis cineraria, and Acacia leucophloea were used to prepare the aqueous leaf leachates for quantifying tryptophan with ultra-high-pressure liquid chromatography (UHPLC).
Experiment 4: Seedlings were harvested and total biomass was recorded following 56 days of growth after oven drying for 48 h at 60°C.
Experiment 5: Quantification of tryptophan, IAA and its intermediates at 0 or 6 days after the addition of tryptophan (300 μg/g soil) or sterile water (control) into soils associated with Prosopis juliflora or native species from seven sites.,