The mass of fine litterfall and nutrient circulation through litterfall were determined in four Melrosideros polymorpha/Cibotium spp.-dominated rainforests that differed in substrate age, parent material texture and annual precipitation on Kilauea and Mauna Loa volcanoes on the island of Hawaii. Three of the sites had rates of litterfall of 5.2 Mg ha−1 y−1; the fourth, which was on the most fertile soil, produced 7.0 Mg ha−1 y−1 of litterfall with higher concentrations of nitrogen and phosphorus. Tree ferns of the genus Cibotium cycled relatively large amounts of nitrogen, phosphorus and potassium through litterfall; their contribution to nutrient circulation was disproportionate to their mass in the forest, or in litterfall. The forest on the youngest substrate, which also had the lowest concentrations of nitrogen in litterfall, was fertilized with complete factorial combinations of nitrogen, phosphorus and a treatment consisting of all other plant nutrients. Additions of nitrogen increased the quantity and nitrogen concentration in litterfall during the second year following the initiation of fertilization, while no other treatment had a significant effect. Additions of nitrogen had no effect on litterfall mass or nutrient concentrations in the most nutrient-rich site.

A computer program, OligoWalk, is reported that predicts the equilibrium affinity of complementary DNA or RNA oligonucleotides to an RNA target. This program considers the predicted stability of the oligonucleotide-target helix and the competition with predicted secondary structure of both the target and the oligonucleotide. Both unimolecular and bimolecular oligonucleotide self structure are considered with a user-defined concentration. The application of OligoWalk is illustrated with three comparisons to experimental results drawn from the literature.

RNA transcripts corresponding to the 250-nt 3′ untranslated region of the R2 non-LTR retrotransposable element are recognized by the R2 reverse transcriptase and are sufficient to serve as templates in the target DNA-primed reverse transcription (TPRT) reaction. The R2 protein encoded by the Bombyx mori R2 can recognize this region from both the B. mori and Drosophila melanogaster R2 elements even though these regions show little nucleotide sequence identity. A model for the RNA secondary structure of the 3′ untranslated region of the D. melanogaster R2 retrotransposon was developed by sequence comparison of 10 species aided by free energy minimization. Chemical modification experiments are consistent with this prediction. A secondary structure model for the 3′ untranslated region of R2 RNA from the R2 element from B. mori was obtained by a combination of chemical modification data and free energy minimization. These two secondary structure models, found independently, share several common sites. This study shows the utility of combining free energy minimization, sequence comparison, and chemical modification to model an RNA secondary structure.