The progressive decline in populations of Isoetes sinensis Palmer in China has been attributed to deteriorating water quality; however, no data have been adduced to support this assumption. In this study we identified locations in China that presently have populations of I. sinensis and locations where the species has been extirpated. We measured various water chemistry parameters at these sites, as well as at similar sites within the distribution range of I. sinensis but from where the species has never been recorded. The results indicate that distribution and occurrence of I. sinensis are closely correlated with water chemistry. Water samples drawn from habitats from where I. sinensis has been extirpated had higher concentrations of heavy metal ions, particularly chr;, dum VI (cr63. In addition, these samples consistently yielded higher readings for dissolved carbon dioxide, water hardness, and concentration of nitrates."uthor for correspondence (wangqf97@public.wh.hb.cn)

Background Seed germination is a series of ordered physiological and morphogenetic processes and a critical stage in plant life cycle. Tamarix hispida is one of the most salt-tolerant plant species; however, its seed germination has not been analysed using combined transcriptomics and metabolomics. Results Transcriptomic sequencing and widely targeted metabolomics were used to detect the transcriptional metabolic profiles of T. hispida at different stages of seed germination and young seedling growth. Transcriptomics showed that 46,538 genes were significantly altered throughout the studied development period. Enrichment study revealed that plant hormones, such as auxin, ABA, JA and SA played differential roles at varying stages of seed germination and post-germination. Metabolomics detected 1022 metabolites, with flavonoids accounting for the highest proportion of differential metabolites. Combined analysis indicated that flavonoid biosynthesis in young seedling growth, such as rhoifolin and quercetin, may improve the plant’s adaptative ability to extreme desert environments. Conclusions The differential regulation of plant hormones and the accumulation of flavonoids may be important for the seed germination survival of T. hispida in response to salt or arid deserts. This study enhanced the understanding of the overall mechanism in seed germination and post-germination. The results provide guidance for the ecological value and young seedling growth of T. hispida.

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