Spermidine priming promotes germination of deteriorated seeds and reduced salt stressed damage in rice seedlings

Abstract

Deterioration of seeds is an important problem leading to low germination and uneven crop establishment causing poor crop growth and productivity. Soil salinity is another factor limiting crop cultivation. Spermidine (Spd) is a compound widely reported for diminishing adverse effects of salt stress in plants. In this study, the effects of Spd priming on normal and deteriorated rice seeds were investigated under salt stress during germination and young seedling stages. Rice seeds were primed with H2O and Spd solutions for 24 h before germination. All rice seeds were grown in Petri dishes containing 5 ml of deionized water with 0 (control) or 150 mM NaCl (salt treatment) for 1-10 d. The results showed that priming groups had higher germination percentage (GP) and germination index (GI) in both normal and deteriorated seeds. Moreover, deteriorated seeds primed with 0.5, 1.0 and 1.5 mM Spd showed significantly higher GP and GI than H2O-primed and non-primed seeds. During early hours of hydration, Spd-primed seeds produced reactive oxygen species (ROS) faster and at higher level than non-priming and H2O priming groups in both control and saline conditions. Earlier accumulation of ROS was associated with more rapid germination. In young seedlings, salinity stress caused a marked decrease in growth and increased membrane damage indicated by higher malondialdehyde (MDA) and electrolyte leakage (EL). Conversely, Spd priming increased growth and reduced membrane damage of rice seedlings established from normal and deteriorated seeds under salt stress. The finding suggested that Spd priming can effectively improve germination of deteriorated seeds and enhance seedling growth under control and salt stress conditions.