供氮水平对菠菜营养品质和体内抗氧化酶活性的影响

通过水培实验，研究了供氮水平对菠菜营养品质和抗氧化酶活性的影响.结果表明，供氮水平由4 mmol·L^-1增加到8 mmol·L^-1，菠菜产量显著增加,叶片中的维生素C（Vc）含量随着供氮浓度由4 mmol·L^-1提高到8 mmol·L^-1，再提高供氮水平，Vc含量则明显下降.叶片硝酸盐含量随着氮浓度的提高而增加.供氮浓度从4 mmol·L^-1增加到8 mmol·L^-1，叶片可溶态草酸含量略有下降，再提高供氮水平则明显上升，而草酸总量随供氮水平提高，先显著升高然后略有降低.SOD和POD酶的活性随供氮水平由4 mmol·L^-1提高到8 mmol·L^-1而增加，再提高供氮水平，酶活性显著下降；CAT活性随供氮水平的增加而降低，叶片MDA含量先降低后显著升高，而游离脯氨酸含量随氮水平的升高而增加.可见供氮水平为8 mmol·L^-1时，菠菜叶片具有较高的生物量、Vc含量和抗氧化酶活性，较低的硝酸盐和草酸含量以及较低的MDA和游离脯氨酸含量，表明供氮浓度8 mmol·L^-1有利于提高菠菜的产量、营养品质和抗逆能力，是菠菜生长较适宜的供氮水平.

Effects of nitrogen supply on nutritional quality and antioxidative enzyme activities of spinach

A hydroponic experiment was carried out to study the effects of nitrogen (N) supply on the nutritional quality and antioxidative enzyme activities of spinach. The results showed that when the N supply increased from 4 to 8 mmol x L(-1), the biomass of spinach and its leaf vitamin C (Vc) content increased significantly, but a further increase of the N supply induced an obvious decrease of Vc content. An increasing N supply increased the nitrate content in leaves. The soluble oxalate content in leaves decreased slightly with the N supply from 4 to 8 mmol x L(-1) N, but increased with a further increase of supplied N. Total oxalate content increased firstly, and then decreased with increasing N supply. SOD and POD activities increased with the N level up to 8 mmol x L(-1) N, but drastically decreased with increasing N levels. CAT activity decreased when N level elevated. MDA content decreased firstly and then increased with increasing N levels, while free proline content decreased with increasing N supply. All of these indicated that 8 mmol x L(-1) N was an appropriate N supply level for spinach to improve its biomass, nutritional quality, and resistance.