An increasing amount of evidence indicates that N can be transferred between plants. Nonetheless, a number of fundamental questions remain. A series of experiments was initiated in the field to examine N transfer between N 2 -fixing soybean (Glycine max [L.] Merr.) varieties and a non-nodulating soybean, and between N 2 -fixing peanut (Arachis hypogaea L.) or soybean and neighboring weed species. The experiments were conducted in soils with low N fertilities and used differences in N accumulation and/or 15 N natural abundance to estimate N transfer. Mixtures of N 2 -fixing and non-nod soybean indicated that substantial inter-plant N transfer occurred. Amounts were variable, ranging from negligible levels to 48% of the N found in the non-nod at maturity. Transfer did not appear to strongly penalize the N 2 -fixing donor plants. But, in cases where high amounts of N were transferred, N content of donors was noticeably lowered. Differences were evident in the amount of N transferred from different N 2 -fixing donor genotypes. Results of experiments with N 2 -fixing crops and the weed species prickly sida (Sida spinosa L.) and sicklepod (Senna obtusifolia [L.] Irwin & Barneby) also indicated substantial N transfer occurred over a 60-day period, with amounts accounting for 30-80% of the N present in the weeds. Transfer of N, however, was generally very low in weed species that are known to be non-hosts for arbuscular mycorrhizae (yellow nutsedge, Cyperus esculentus L. and Palmer amaranth, Amaranthus palmeri [S.] Watson). The results are consistent with the view that N transfer occurs primarily through mycorrhizal hyphal networks, and they reveal that N transfer may be a contributing factor to weed problems in N 2 -fixing crops in low N fertility conditions.

Evidence from past studies suggests that loblolly pine may be tolerant of Al. The experiments described in this manuscript were initiated to examine Al tolerance and Al accumulation in the pine root and the degree of Al accumulation in fungal hyphae when pine roots were colonized with the ectomycorrhiza Pisolithus tinctorius . The experiments used lumogallion staining and confocal microscopy to localize Al in root and fungal structures. The results clearly showed that loblolly pine seedlings were highly resistant to Al. A decrease in primary root extension could not be detected until Al +3