Characteristics of Lycium ruthenicum adapting to salinization stress after salt tolerance training

  Objective  For soil salinization restoration and sustainability in extreme arid areas, we investigated Lycium ruthenicum adapting to long-term salinization stress.

  Method  The K⁺, Na⁺ and Ca²⁺ compartmentalization of organs of L. ruthenicum in low salt stress (MSS), middle salt stress (HSS) and high salt stress (SS) soil were analyzed by regression analysis and principal component analysis, as well as the responses of dry mass and root morphology to salt stresses.

  Result  (1) If concentration of NaCl at soil solution was below 183.63 mmol/L, the survival rate of salt-tolerance training plants increased with increasing concentration of NaCl, and all the plants died if concentration of NaCl was above 355.88 mmol/L. With increase of NaCl concentration, the relative growth rate of fruit significantly slowed down from flowering to early fruit, while accelerated from early fruit to full maturity. (2) The root K⁺ and Na⁺ treated by HSS were significantly higher than those treated by MSS and SS, and the contents of K⁺, Na⁺ and Ca²⁺ in stems were significantly lower than those treated by MSS and SS. There was significant differences neither K⁺/Na⁺ nor Ca²⁺/Na⁺ between roots and stems in HSS. The leaf Ca²⁺ in SS treatment was 5 and 3 folds of MSS and HSS, respectively. There was no significant difference in Na⁺ content between roots and stems, and no significant difference in Ca²⁺ content between roots and leaves. The stress increased from MSS to SS, the content of Na⁺ in the stem increased by 0.78 g/kg on average. (3) PCA analysis showed that principal component 1 (PCA1) and principal component 2 (PCA2) explained 73.9% information of L. ruthenicum under salt stress. PCA1 explained 57.8% of the salt stress of L. ruthenicum. Among them, dry mass of over-ground organs contributed the most to PCA1. According to these contributions to PCA1, leaf dry mass, stem dry mass, root dry mass and taproot diameter were to be top four. PCA1 was negatively correlated with Na⁺ content both in roots and aboveground organs and lateral root diameter. Plant height, root Ca²⁺ content, stem diameter, aboveground organ K⁺/Na⁺, root dry mass and taproot diameter were positively correlated with PCA1. The content of plant K⁺/Na⁺, root K⁺/Na⁺, rhizosphere soil K⁺/Na⁺, root Ca²⁺ and aboveground organ Ca²⁺ could explain 16.1% of PCA2.

  Conclusion  With the increase of salt stress, leaves maintained high concentration of Ca²⁺ to regulate plant K⁺/Na⁺, and root and stem enrichment and storage capacity of Na⁺ were significantly enhanced, which indicate that L. ruthenicum tends to share salt stress cooperatively in different organs to adapt to long-term salt stress after salt tolerance training.