Fructan, sucrose and related enzyme activities are preserved in timothy (Phleum pratense L.) during wilting

摘要

Timothy (Phleum pratense L.) is an important forage grass used for pasture, hay and silage in regions with cool and humid growth seasons. Harvesting conditions could reduce its nutritive value, particularly with extended wilting periods. To understand how daytime or night-time wilting influences the nutritive value of timothy, this study investigated the metabolism of non-structural carbohydrates, including fructan and starch, together with total soluble protein and amino acid patterns in timothy plants harvested at two maturity stages (heading and anthesis) and wilted under controlled conditions for 24h at two temperatures (15 degrees C, 20 degrees C) and two light regimes (darkness, light) by simulating different wilting management practices. Correlation analysis with the whole dataset showed that soluble protein, glucose and starch contents declined in plant tissues concomitantly with water loss, while amino acid, sucrose and fructose contents increased. Transient increase in amino acid content suggests that the decrease in protein content was due to proteolysis during wilting. Sucrose and fructose contents generally increased in plant tissues harvested at anthesis and wilted in light whereas they were unaffected in plants wilted in darkness. Fructan content remained stable. Fructan exohydrolase (FEH) and soluble acid invertase (INV) activities were well preserved during the first 12h of wilting and might facilitate the fermentation process at the beginning of ensiling by supplying fructose from fructans and hexoses from sucrose to the fermentive bacteria.