Hibiscus hamabo Sieb. et Zucc is an important semi-mangrove plant with great morphological features and strong salt resistance. In this study, by combining single molecule real time and next-generation sequencing technologies, we explored the transcriptomic changes in the roots of salt stressed H. hamabo. A total of 94,562 unigenes were obtained by clustering the same isoforms using the PacBio RSII platform, and 2269 differentially expressed genes were obtained under salt stress using the Illumina platform. There were 519 differentially expressed genes co-expressed at each treatment time point under salt stress, and these genes were found to be enriched in ion signal transduction and plant hormone signal transduction. We used Arabidopsis thaliana (L.) Heynh. transformation to confirm the function of the HhWRKY79 gene and discovered that overexpression enhanced salt tolerance. The full-length transcripts generated in this study provide a full characterization of the transcriptome of H. hamabo and may be useful in mining new salt stress-related genes specific to this species, while facilitating the understanding of the salt tolerance mechanisms.

To understand the characteristics of net NH₄⁺ and NO₃⁻ fluxes and their relation with net H⁺ fluxes in Taxodium, net fluxes of NH₄⁺, NO₃⁻ and H⁺ were detected by a scanning ion-selective electrode technique under different forms of fixed nitrogen (N) and experimental conditions. The results showed that higher net NH₄⁺ and NO₃⁻ fluxes occurred at 2.1–3.0 mm from the root apex in T. ascendens and T. distichum. Compared to NH₄⁺ or NO₃⁻ alone, more stable net NH₄⁺ and NO₃⁻ fluxes were found under NH₄NO₃ supply conditions, of which net NH₄⁺ flux was promoted at least 1.71 times by NO₃⁻, whereas net NO₃⁻ flux was reduced more than 81.66% by NH₄⁺ in all plants, which indicated that NH₄⁺ is preferred by Taxodium plants. T. ascendens and T. mucronatum had the largest net NH₄⁺ and total N influxes when NH₄⁺:NO₃⁻ was 3:1. ¹⁵N Atom% and activities of N assimilation enzymes were improved by single N fertilization in the roots of T. distichum. In most cases, net H⁺ fluxes were tightly correlated with net NH₄⁺ and NO₃⁻ fluxes. Thus, both N forms and proportions could affect N uptake of Taxodium. These findings could provide useful guidance for N management for better productivity of Taxodium plants.