Exogenous Application of Abscisic Acid (ABA) Enhances Chilling Tolerance in Seedlings of Napier Grass (Pennisetum purpureum Schum.)

Napier grass,an important forage crop with potentials in multi-purpose applications,is widely grown throughout the tropics and subtropics.Low temperature severely limits its productivity and geographical distribution in temperate regions of the world.In this study,we investigated the effect of exogenous abscisic Acid (ABA) on chilling tolerance of napier grass (Pennisetum purpureum Schum.) seedlings.Seven-day-old napier grass seedlings were cultured in ddH2O or ABA solution at different concentrations and exposed to 1 ℃ for different time durations.The chilling injury,membrane stability index (MSI) and proline content were estimated from leaf samples.The results showed that there was obvious morphological injury of leaf blighting and restrained growth for the seedlings under chilling stress,but this damage can be largely reduced (by 2/3) when the seedlings were treated by 100 μmol/L ABA in the culture solution,and that the application of exogenous ABA can help to maintain a good stability of leaf cell membrane as expressed by a high MSI value and a low level of proline in leaf cells.These results suggested that exogenous ABA can significantly alleviate chilling injury in napier grass seedlings by maintaining the stability of leaf cell membrane during chilling stress,and that the chilling tolerance was not ensured by a proline accumulation although a passive accumulation of proline was observed in the seedlings under chilling stress.Our results lay a preliminary foundation for future investigations on the molecular mechanisms of ABA induced chilling or freezing tolerance in napier grass.