Response of Grass Seedlings to Smoke-Water and Smoke-Derived Butenolide in the Absence of Macronutrients (Nitrogen, Phosphorus, and Potassium)

Abstract

Abstract Compositional transformation of South African semiarid grasslands and savannas owing to changes in soil nutrient status and fire-linked attributes is often reported. However, mechanisms of change are not fully understood. Currently, plant-derived smoke has attracted much attention as a fire-related cue responsible for stimulating germination and seedling growth. However, there is very little documentation on how these fire-linked factors, such as smoke, and soil macronutrients, such as nitrogen (N), phosphorus (P), and potassium (K), interact to effect seedling growth of grasses. In this study, smoke-responsive ( Themeda triandra ) and less smoke-responsive species ( Eragrostis curvula and Panicum maximum ) were tested with different concentrations and combinations of smoke-water and smoke-isolated butenolide with or without added N, P, or K under greenhouse conditions. In the absence of N, P, or K, smoke-water and butenolide treatments enhanced a number of seedling growth parameters of T. triandra . In contrast, exclusion of N from the nutrient solution significantly reduced shoot length, seedling weight, root volume, and vigor index of E. curvula at all tested concentrations of smoke-water and butenolide solutions compared to the control. In the presence of N, P, and K, smoke-water and butenolide suppressed seedling growth of P. maximum , whereas the absence of one of these macronutrients had a small promotory effect on some parameters. This study may assist in understanding the postfire seedling dynamics of grasses.