We used Pisolithus tinctorius and Cenococcum geophilum to determine the copper (Cu) resistance of ectomycorrhizal (ECM) fungi and their potential for improving phytoremediation of Cu-contaminated soil by Chinese red pine (Pinus tabulaeformis). The results showed that nutrient accumulation in C. geophilum mycelium was significantly lower under higher Cu concentrations in the soil, which was not observed in P. tinctorius. Meanwhile, P. tinctorius exhibited greater Cu tolerance than C. geophilum. Inoculation with ECM fungi significantly improved the growth of pine shoots planted in polluted soil in pot experiments (p < 0.01). The total accumulated Cu in pine seedlings planted in Cu-contaminated soil increased by 72.8% and 113.3% when inoculated with P. tinctorius and C. geophilum, respectively, indicating that ECM fungi may help their host to phytoextract heavy metals. Furthermore, the majority of the total absorbed metals remained in the roots, confirming the ability of ECM fungi to promote heavy metal phytostabilization. There were no differences between the effects of the two fungi in helping the host stabilize and absorb Cu, even though they have different Cu tolerances. Inoculation with ECM fungi can benefit plant establishment in polluted environments and assist plants with phytoremediating heavy-metal-contaminated soils.
The purslane Portulaca oleracea L. is a promising crop species for agriculture in saline-alkali soils. Up to date, biochemical and molecular changes in purslane in response to salinity were seldom reported. To investigate biochemical effects of salinity on purslane, seedlings were treated with different concentrations of NaCl for up to 14 days. The results showed that treatments with 150 mM and 200 mM NaCl significantly decreased dry and fresh weight of seedlings, shoot and root length as well as leaflet number on main stem, demonstrating inhibition on purslane growth. Treatments with 100-200 mM NaCl significantly decreased net photosynthetic rate, increased intercellular CO 2 concentration, MDA content and production rate of O 2 − , induced activities of SOD, POD and CAT, suggesting inhibition on photosynthesis and induction of oxidant stress. With longer exposure time, activities of antioxidant enzymes showed decreasing tendency, probably due to denaturation of proteins and damages of cell membrane. In treatments with 150 mM and 200 mM NaCl, Na + content increased in purslane leaf, stem and root, which then decreased K + content, probably due to membrane depolarization and regulation of ion channels. Moreover, transcriptome profiles in leaves were compared among treatments with 200 mM for 0, 2, 6, 12 and 24 h. The results suggested that saline treatments down-regulated transcription levels of genes involved in photosynthesis, energy metabolism, lignin biosynthesis and signaling transduction. Overall, the present study uncovered biochemical and molecular responses of purslane to salinity, which should be useful for agriculture of purslane on saline-alkali soils.
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