Effects of salt stress on growth, photosynthesis and solute accumulation in three poplar cultivars

This study compared the effects of salt (NaCl) stress on growth, photosynthesis and solute accumulation in seedlings of the three poplar (Populus bonatii) cultivars Populus x BaiLin-2 (BL-2), Populus x BaiLin-3 (BL-3), and Populus x Xjiajiali (XJJL). The results showed that BL-2 and BL-3 could not survive at a salinity level of 200 mM but XJJL grew well. The effect of moderate salt stress on leaf extension of the three cultivars was only slight. At a high level of salinity, however, NaCl clearly inhibited leaf extension of BL-2 and BL-3, whereas it did not affect that of XJJL, and the net photosynthetic rate (P (N)) in XJJL was much higher than those of BL-2 and BL-3. The lower P (N) of BL-2 and BL-3 might be associated with the high concentration of Na+ and/or Cl- accumulated in the leaves, which could be toxic in photosynthesis system. In summary, the greater salt-tolerance of XJJL compared with that of BL-2 and BL-3 might be explained by the higher P (N) and photosynthetic area, the lower Na+/K- ratio and Cl- in the leaf, and the greater accumulation of soluble sugars and SO4 (2-).