Effects of Biostimulants and Other Biological Byproduct Extracts On the Heat Tolerance Associated with Root Growth, Visual Quality, and Chlorophyll Index of Perennial Ryegrass.

Published research has indicated that perennial ryegrass (Lolium perenne L.), a common economically important cool-season turfgrass species, exogenously treated with a biostimulant exhibited improved photochemical efficiency and leaf membrane thermostability at high air temperature stress (~36°C) in growth chamber studies, suggesting improved overall metabolic responses to heat stress.  In this study, the effects of several different biostimulant and biological byproduct extracts on the heat tolerance of perennial ryegrass were investigated.  Physiological responses of perennial ryegrass treated with or without several different types of foliar-applied humic substances, hormone-containing products, and amino acid-containing products and subjected to three separate, consecutive 2-wk air temperature stresses (~25°C, ~31°C, and ~42°C ) followed by drought stress were investigated in the greenhouse.  Multiple rates and applications were also investigated for some, but not all, treatments.  Daily maximum and minimum temperatures, root growth, turfgrass visual quality, chlorophyll index, amount of leaf firing, and topgrowth digital analysis were measured.  Following the terminal drought period, root dieback was also measured.  Results will be discussed.