屎肠球菌胞外多糖对镉胁迫下水稻种子萌发及幼苗生长的影响

Effect of exopolysaccharide from Enterococcus faecium on rice seed germination and seedling growth under cadmium stress

为研究屎肠球菌胞外多糖对Cd胁迫条件下水稻种子萌发及幼苗生长的影响,采用水培试验法,在含有Cd(20、40 mg·L-1)的培养液中添加不同浓度胞外多糖(500、1 000 mg·L-1),考察水稻种子萌发及幼苗生长相关代谢指标的变化。试验结果表明,Cd胁迫明显抑制了水稻种子的萌发效率与幼苗各器官的发育情况,而添加不同浓度的屎肠球菌胞外多糖可以显著促进Cd胁迫下水稻种子的发芽势、发芽率和根部发育,但水稻萌发后的芽长受到显著抑制,而这种抑制作用在水稻幼苗生长阶段并未观察到。在Cd胁迫条件下,胞外多糖处理后的水稻幼苗内类黄酮与花色素苷的含量提高了18.6%~208.7%,超氧化物歧化酶、过氧化物酶的活力显著上升,丙二醛含量显著下降。傅里叶变换红外光谱显示胞外多糖提高了Cd胁迫下水稻叶片中碳水化合物、蛋白质、脂类和羧酸盐的含量,并可能通过加强渗透作用来降低Cd对水稻的毒害作用。研究结果表明,屎肠球菌胞外多糖可以显著缓解Cd胁迫对水稻种子萌发与幼苗生长的毒害作用。

The effect of Enterococcus faecium exopolysaccharide(EPS)on rice seed germination and seedling growth under Cd stress was investigated.Different concentrations of EPS(500 mg·L-1 and 1000 mg·L-1)were added to the culture medium that contained Cd(20 mg·L-1 and 40 mg·L-1)to investigate the metabolic changes of rice seed germination and seedling growth.The results showed that Cd stress significantly inhibited the germination efficiency of rice seeds and decreased the development of various organs of the seedlings,whereas the addition of different concentrations of EPS(500 mg·L-1 and 1000 mg·L-1)significantly improved the germination potential,germination rate,and root development of rice seeds under Cd stress;however,the germination of rice buds was significantly inhibited after germination.This inhibition was not observed during the growth stage of the rice seedlings.Under Cd stress,the content of flavonoids and anthocyanins in the rice seedlings treated with EPS increased 18.6%~208.7%and the activity of superoxide dismutase and peroxidase also increased,whereas the malondialdehyde content decreased significantly.Results from the fourier transform infrared test showed that the contents of carbohydrates,proteins,lipids,and carboxylates in rice leaves were increased with the addition of EPS under Cd stress,which might decrease the toxic effect of Cd in rice by enhancing the osmotic effect in leaves.The results of this study indicate that the EPS of E.faecium can significantly mitigate the toxic effects of Cd stress on rice seed sprouting and seedling growth.