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.
Saline and sodic soils are typical stressful soil types in arid and semiarid coastal regions and in regions of poor natural drainage. There are approximately 954 million hectares of saline and sodic soil worldwide. Due to high salinity, high sodicity and sometimes high pH value, these soils have poor physical and chemical properties and are difficult for common plants to grow in, thus becoming more and more barren [1]. Coastal mud flat generally show high saline content and sodicity. Different from traditional saline and sodic soil, coastal mud flat is located in intertidal area and often receives runoff and seawater rich of nutrients. It is neither dry nor barren, since it is efficient sediment traps that facilitate the accumulation and storage of organic matters from water column and from below ground production [2]. Thus, coastal mud flats are potential land resources for agriculture and ecological landscape construction [3]. Jiangsu Province has the largest area of coastal mud flats in China, approximately equal to 5,000 km 2. To utilize these areas, seawater-cultivated vegetables were introduced, which can endure high salinity and
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