Detecting Physiological Response of Tall Fescue to Salinity Stress Based On Single Leaf Spectrums.

Turfgrass visual quality is one of the most important components of turf quality.  Leaf firing, a form of chlorosis, often is the most obvious symptom developed when the grass is under salinity stress.  The objective of this study was to investigate the process of leaf senescence under natural, shade, and saline conditions.  Two tall fescue varieties, previously reported as salt tolerant (Tar Heel II) and sensitive (Wolf Pack), were investigated in this study.  We added NaCl and CaCl₂ to the full strength Hoagland solution to a final EC about 25 dS m^-1 to mimic saline stress.  The salt solution was applied at seven-day intervals to the sand root zones for the salinity treatment.  A shade material that allowed passing of 30% light to simulate accelerated aging.  Plants treated with Hoagland solution only were used as control.  Single leaf normalized vegetation index (NDVI) and quantum yield of photosynthesis system II (PSII) were measured from the fourth up to the newest fully opened leaves.  We also measured relative leaf growth rate, tiller appearing rate, biomass, and relative distribution of K, Na, Ca, Mg and Fe in shoots and roots of the plants.  Older leaves showed more reduction in NDVI and quantum yield of PSII than younger leaves in response to the salinity treatment, with the newest fully opened leaves showing no differences between treatments.  Both salinity and accelerated aging reduced root and shoot biomass but the root/shoot ratio was only decreased in the accelerated aging by shade treatment.