一氧化氮对甘蔗锰积累的影响

近年来在广西主要的甘蔗种植区出现了土壤中锰含量过高所导致的甘蔗宿根蔗幼苗黄化问题,这严重降低了甘蔗的产量和品质,制约了甘蔗产业发展。一氧化氮（NO）是植物体内介导植物响应重金属胁迫的信号分子,在缓解重金属毒害方面起着重要作用。采用水培试验方法研究了锰胁迫下NO积累与甘蔗植株锰含量及细胞壁多糖组分的关系,旨在为揭示甘蔗锰毒耐受机制提供科学依据。结果表明,锰处理后植株锰含量显著增加,并且植株中的锰主要积累在细胞壁及其果胶组分中;0.5、1.0 mmol/L锰处理24 h,后根尖中NO的积累量显著增加。在0.5 mmol/L锰溶液中添加NO供体硝普钠（SNP,0.2 mmol/L）增加植株NO积累后,根系锰含量为1215.4 mg/kg,叶片锰含量为525.5 mg/kg,相对于对照增加了37.1%,根及叶片中的锰含量、根细胞壁及其果胶组分中的锰含量均显著增加;一氧化氮清除剂（cPTIO,0.1 mmol/L）处理后,有效减少植株NO积累,并降低了根系、根系细胞壁及细胞壁果胶组分中的锰含量,根系锰含量相较于对照降低了78.2%,根系细胞壁和细胞壁果胶的锰含量相对于对照分别降低57.4%、40.6%;与此相同,硝酸还原酶抑制剂钨酸钠（0.3 mmol/L）处理抑制了硝酸还原酶（NR）活性并降低了植株NO积累,甘蔗植株、根系细胞壁及其果胶组分中的锰含量均显著下降。虽然钨酸钠处理后根系细胞壁中的半纤维素I和半纤维素II组分含量变化不显著,但细胞壁果胶组含量、果胶甲酯酶活性以及果胶去甲酯程度显著降低,从而减少了细胞壁的锰吸附。可见,锰胁迫引起甘蔗细胞积累NO,而NO通过调控细胞壁的多糖组分及果胶甲酯化程度介导植株锰积累与分布。

Mechanisms of Manganese Accumulation in Sugarcane Seedling by Nitric Oxide Signaling Pathway

Sugarcane, as an important tropical crop in China, is mainly planted in subtropical acidic soil areas. In recent years, in the main sugarcane growing areas of Guangxi, the problem of the yellowing of sugarcane seedlings caused by excessive manganese in the soil has seriously reduced the yield and quality of sugarcane and restricted the development of sugarcane industry. Nitric oxide (NO) is a signal molecule that mediates plant response to heavy metal stress, and plays an important role in alleviating heavy metal toxicity. In order to explore the effect of NO on manganese stress in sugarcane, the relationship between NO accumulation and manganese content and polysaccharide components in sugarcane cell wall under manganese stress was studied by the hydroponic experiment in order to provide scientific basis for revealing the mechanism of manganese toxicity in sugarcane. The manganese content in plants increased significantly after manganese treatment, and the manganese content was mainly accumulated in cell wall and pectin components. After treatment with 0.5 and 1.0 mmol/L manganese for 24 h, the accumulation of NO in root tips significantly increased. After adding NO donor sodium nitroprusside (SNP, 0.2 mmol/L) in 0.5 mmol/L manganese solution, the accumulation of NO in plants increased, The manganese content in roots was 1215.4 mg/kg, and that in leaves was 525.5 mg/kg, which increased by 37.1% compared with the control. The manganese content in root and leaf, root cell wall and pectin components increased significantly. Nitric oxide scavenge (cPTIO, 0.1 mmol/L) could effectively remove NO accumulation in plants, and reduce root manganese content and root cell wall and pectin content. Root manganese content decreased by 78.2%, root cell wall and root cell wall pectin manganese content decreased by 57.4% and 40.6%, respectively. Similarly, nitrate reductase inhibitor sodium tungstate (0.3 mmol/L) inhibited nitrate reductase (NR) activity and reduced NO accumulation in plants, and manganese content in sugarcane, root cell wall and its pectin components decreased significantly. Although the content of hemicellulose I and hemicellulose II in the root cell wall was not significantly changed after sodium tungstate treatment, the pectin group content, pectin methyl esterase activity and the degree of methyl demethylation of pectin significantly decreased, thus reducing manganese adsorption on cell walls. It can be seen that manganese causes the accumulation of NO in sugarcane cells, and NO mediates the accumulation and distribution of manganese in sugarcane plants by regulating the polysaccharide components of cell wall and the degree of pectin methylation.