Regrowth mechanism of ryegrass with different stubble heights by cytokinin

The regrowth mechanism of ryegrasses (Lolium multiflorum) with different stubble heights was investigated. Experiments with different photoperiod were conducted. Results showed that the plants in darkness with low stubble height had significant lower leaf regrowth biomass (P＜0.05) compared with the plants with high stubble height and root clipping. Total biomass index which showed the variation of total organic substances during regrowth with single stubble was used to evaluate leaf regrowth with different stubble heights with the minimized influence of stubble stored organic substances. The plants with light, single clipping and low stubble height had higher total biomass index. The plants with light, frequent clipping and high stubble height also had higher total biomass index. Concentrations of zeatin and zeatin riboside (Z+ZR) and abscisic acid (ABA) in leaves and xylem sap from the plants with light were measured and showed that total biomass index had positive correlation with leaf Z+ZR concentrations which adjusted by roots. It can be concluded that root-induced leaf cytokinin was critical factor affecting ryegrass regrowth at different clipping heights