Abstract

Ryegrass (Lolium multiflorum Lam. cv. Blue Heaven) is an annual forage cultivar for more than one-half of the carrying capacity. Because ryegrass is dependent on water availability, drought during emergence severely affects grain yield in a global warming world. In this research, the dynamic profile of drought-inducible metabolic response was determined. Compared with well-watered conditions (1st day), from the 2nd to 14th day after stress, the ryegrass samples were collected every two days and measured for the content of total saccharides, sucrose, glucose, ascorbic acid, free amino acid, total polyphenol, chlorophyll, reduced and oxidative glutathione, reactive oxidative species, malondialdehyde, superoxide anion, cellulose, lignin and hemicellulose. Under the daily evaporation of 27.18 ± 3.4 g/day, the dynamic response to drought tolerance of ryegrass fluctuated on the whole rather than linear change. The first eight days had light and moderate drought stress, and ryegrass actively reduced the drought stress damage through the metabolic and antioxidant system. After eight days, ryegrass suffered from severe stress, and its metabolic and antioxidant system were collapsed and plants died. The dynamic response to light and moderate stress (the first 8 days) were not consistent with that of severe stress (last 6 days) and even had opposite results. Therefore, it is necessary to determine the optimized treatment by dynamic monitoring in drought stress. More importantly, optimal daily evaporation, moderate and severe stress should be selected according to the needs of drought tolerance research. Overall, this study provided a novel and comprehensive insight of the dynamic response to drought stress.