This study aimed to investigate the interaction effect of spermidine (Spd) and salinity stress on growth, photosynthetic rate, antioxidant system and free polyamines (PAs) contents of goosegrass (Eleusine indica L.) seedlings. E. indica was raised in a growth chamber under normal and toxic salt stress (100 mM of NaCl) and sprayed with 0 and 1.00 mM of Spd. The degree of growth inhibition caused by salt stress was lower in a paraquat‐resistant (R) biotype compared to a paraquat‐susceptible (S) biotype. Salt stress significantly elevated the accumulation of malondialdehyde, electrolyte leakage and proline and resulted in the degradation of chlorophyll; reduction in chlorophyll fluorescence; and a decrease in photosynthetic rate, relative water content and biomass. Spd‐treated plants maintained higher activities of antioxidant enzymes (catalase, superoxide dismutase and peroxidase), a greater rate of photosynthesis and lower osmotic pressure than untreated plants in the S biotype. Endogenous Spd content was reduced significantly in response to salt stress in both biotypes, but free PAs content in the S biotype was remarkably enhanced with exogenous Spd application under normal or salinity stress conditions. The result indicated that the S biotype was more sensitive to salinity than the R biotype; meanwhile, exogenous Spd maybe play an important role in protecting S biotype plants from salt stress.

中文翻译：

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亚精胺和盐分胁迫对百草枯和抗药性猕猴桃（Eleusine indica L.）生长和生化反应的影响

本研究旨在探讨亚精胺（SPD）和盐分胁迫对生长，光合速率，抗氧化系统和免费多胺的牛筋草（PAS），内容（互动效应牛筋L.）幼苗。E.籼稻在正常和有毒的盐胁迫（100 mM NaCl）下，在生长室中将其生长，并用0和1.00 mM Spd喷雾。与百草枯敏感性（S）生物型相比，百草枯抗性（R）生物型由盐胁迫引起的生长抑制程度要低。盐胁迫显着提高了丙二醛的积累，电解质的泄漏和脯氨酸的含量，导致叶绿素的降解。叶绿素荧光减少；降低了光合速率，相对含水量和生物量。与S生物型植物相比，经Spd处理的植物具有更高的抗氧化酶（过氧化氢酶，超氧化物歧化酶和过氧化物酶）活性，更高的光合作用率和较低的渗透压。在两种生物型中，内源Spd含量均响应盐胁迫而显着降低，但在正常或盐分胁迫条件下，外源施用Spd可以显着提高S生物型中游离PA的含量。结果表明，S生物型比R生物型对盐分敏感。同时，外源Spd可能在保护S生物型植物免受盐胁迫中起重要作用。