Research paperGrowth, root compensation and ion distribution in Lycium chinense under heterogeneous salinity stress

- A woody plant Lycium chinense was studied by split-root experiment under non-uniform salinity conditions.
- Under heterogeneous salinity, the fine roots of Lycium chinense had proliferated in the lower salinity zone.
- The total fine root was not decreased and salt stress had alleviated if the salinity of half root zone was within a suitable range.
- The leaf Na+, Cl− and soluble sugar contents of Lycium chinense were maintained at an unstressed level.

A split-root experiment was conducted to study the growth of the woody plant Lycium chinense under non-uniform salinity conditions and investigate the growth, root distribution and ion accumulation under uniform and heterogeneous NaCl stress. Four uniform salinity treatments with increasing concentrations of NaCl in the nutrient solution (0, 170, 340, and 510 mM) and 6 heterogeneous salinity treatments with different concentrations of NaCl (0/170, 0/340, 0/510, 170/340, 170/510, and 340/510 mM) were applied to two sides of split root pots. The results showed that L. chinense growth decreased with increasing uniform salinity when the salinity was higher than 170 mM. Under heterogeneous salinity stress, growth was not inhibited, except in the plants treated with 340/510 mM NaCl. The leaf net photosynthesis rate and transpiration rate were close to the mean root zone salinity, and stomatal conductance was mainly influenced by higher salinity. Fine roots proliferated in the lower salinity zone, which resulted in a stable total root volume as long as the salinity of one-half of the pot was within a suitable range. The root compensation effect was stronger when the salinity difference of the root zones was larger. Under heterogeneous salinity, the leaf Na+ and Cl− contents were maintained at a moderate level, and the leaf soluble sugar content was also within a normal range. These results suggest that the increased fine roots in the lower salinity zone and the moderate leaf Na+ and Cl− contents alleviated salt stress. Thus, partial lower salinity zones can be created in heavily saline soil for the cultivation of woody plants.