Tissue sodium and chloride concentrations in relation to needle injury in boreal conifer seedlings subjected to salt stress

Abstract

Tissue Na and Cl concentrations can be used for estimation of salt injury for white spruce, black spruce, and jack pine growing at salt affected areas. Elevated soil salinity is among the most challenging environmental factors affecting plant growth and survival. Due to the widespread salinity concerns in agricultural soils, most of the salinity research has been carried out with agricultural crop plants. However, salinity is also frequently a factor affecting the sites reclaimed following surface mining including the oil sands mining areas located in the boreal forest of the northeastern Alberta, Canada. The present study examined the relationship between NaCl uptake, tissue Na and Cl concentrations, and plant injury in seedlings of three conifer species, which are commonly used for oil sands reclamation including black spruce (Picea mariana), white spruce (Picea glauca), and jack pine (Pinus banksiana). The seedlings were grown under controlled-environment conditions in sand culture and were subjected to 0 (control), 30, 60, and 90 mM NaCl treatments. Compared with control, stem diameters and shoot heights of black spruce, white spruce, and jack pine seedlings were significantly reduced by all NaCl treatments. White spruce and jack pine also exhibited reduced total dry weights. Needle chlorophyll concentrations decreased under NaCl treatments in all species. Visible symptoms of salt injury were observed in young and old needles of seedlings treated with NaCl. Significant needle necrosis was present in all species subjected to the 90 mM NaCl treatment. We found significant correlation between needle Na and Cl concentrations and necrosis extent. Therefore, we propose using the tissue Na and Cl concentration as an effective monitoring tool to estimate salt injury of conifers grown in NaCl-affected areas.