Detecting salinity stress in tall fescue based on single leaf spectrum

Salinity problems are becoming more and more severe in turfgrass management, which can cause physiological stress to turfgrass and deteriorate soil structure. Tall fescue (Festuca arundinacea Schreb.) is a cool-season turfgrass with moderate to high tolerance to salinity. The objective of this study was to compare indices of single leaf spectrum and direct physiological parameters in their ability to detect tall fescue responses to salinity stress. Two tall fescue varieties, Tar Heel II (salt tolerant) and Wolfpack (salt sensitive) were established in washed silica sand. At the 4-leaf stage, salinity treatment was applied by adding NaCl and CaCl2 (1:1 w/w) to the Hoagland cultural solution in 16 g L−1, and the control received Hoagland solution only. Relative water content (RWC), total chlorophyll (Chl) content, quantum yield of photosystem II, transpiration rate, and stomatal conductance of the 4th leaf decreased in the salinity treated plants compared to the control, with RWC and Chl showed more sensitivity. At least three indices calculated based on single leaf reflectance spectrum (350–1000 nm), modified simple ratio vegetation index (mSR750/705), modified normalized difference vegetation index (mND750/705), and stress index (SI710/760), were sensitive in differentiation of salinity stress from untreated plants. Three indices also were significantly correlated to the two major physiological parameters. Correlation coefficients of RWC to mSR750/705, mND750/705, and SI710/760 were 0.64, 0.60, and −0.52 on average. Correlation coefficients of Chl to mSR750/705, mND750/705, and SI710/760 were 0.78, 0.79, and −0.68 on average.

► We compared physiological parameters with spectrum indices under salinity stress.
► Three indices from single leaf spectrum were identified sensitive to salinity stress.
► These spectrum indices also were strongly correlated with physiological parameters.