Biosynthesis of Indole-3-Acetic Acid by the Pine Ectomycorrhizal Fungus Pisolithus tinctorius

Previous work has indicated that anatomical and morphological changes (stunting and dichotomy) in roots of various conifers may be influenced by plant-growth-regulating substances secreted by mycorrhizae. Indole-3-acetic acid (IAA) has been tentatively identified as a major auxin produced by some selected ectomycorrhizae. We report the isolation and detection of IAA as a secondary metabolite from Pisolithus tinctorius by thin-layer chromatography, high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent (monoclonal antibody) assay (ELISA), and unequivocal identification by gas chromatography-mass spectrometry (GC-MS). The thin-layer chromatography methods for auxin isolation described here are novel, with the use of heptane-acetone-glacial acetic acid as the migrating solvent and formaldehyde, H(2)SO(4), and vanadate in detection. The acidic extract of the culture supernatant was methylated with ethereal diazomethane to detect IAA as methyl-3-IAA by HPLC, ELISA, and GC-MS. The quantitative amount of IAA detected ranged from 4 to 5 mumol liter by HPLC and ELISA. Another unidentified metabolite was detected by GC-MS with a typical indole nucleus (m/z = 130), indicating that it could be an intermediate in auxin metabolism. Plant response (Pseudotsuga menziesii, Douglas fir) was monitored upon inoculation of P. tinctorius and l-tryptophan. There was a consistent increase in plant height and stem diameter as a result of the two treatments, with statistical differences in dry weights of the shoots and roots.     

Feather isotope analysis discriminates age-classes of Western, Least, and Semipalmated sandpipers when plumage methods are unreliable

ABSTRACT Avian age‐class discrimination is typically based on the completeness of the first prebasic molt. In several calidrid sandpiper species, juvenal flight feathers grown on Arctic breeding grounds are retained through the first three migrations. Thereafter, flight feathers are grown annually at temperate migratory stopover sites during the fall or on the subtropical wintering grounds. Standard methods for distinguishing age classes of sandpipers rely on a combination of traits, including body plumage, coloration of protected inner median covert edges, and extent of flight feather wear. We tested the ability of stable hydrogen isotope ratios in flight feathers (δD_f) to distinguish young birds in their first winter through second fall from older adults in three calidrid sandpiper species, Western (Calidris mauri), Least (C. minutilla), and Semipalmated (C. pusilla) sandpipers. We compared the apparent reliability of the isotope approach to that of plumage‐based aging. The large expected differences in δD_f values of flight feathers grown at Arctic versus non‐Arctic latitudes enabled use of this technique to discriminate between age‐classes. We determined δD_f values of known Arctic‐grown feathers from juveniles that grew their flight feathers on the breeding grounds. Flight feather δD_f values of southward‐migrating adults showed bimodal distributions for all three species. Negative values overlapped with species‐specific juvenile values, identifying putative second fall birds with high‐latitude grown juvenal feathers retained from the previous year. The more positive values identified older adults who grew their feathers at mid‐ and low latitudes. Importantly, δD_f analysis successfully identified first‐winter and second‐fall birds not detected by plumage‐based aging. Flight feather wear alone was a poor basis for age classification because scores overlapped extensively between putative second fall birds and older adults. Flight feather hydrogen isotope analysis enables more definitive assignment of age classes when standard plumage methods are unreliable.