氮营养盐对极北海带幼苗生长和生理生化特性的影响

为研究不同质量浓度硝态氮对极北海带生长、生理特性的影响,在实验室条件下将极北海带培养在硝态氮质量浓度梯度为0、0.5、2、4、6、8、10 mg/L的灭菌海水中,10 d后分别测定各培养条件下藻体的生长和生化参数。试验结果表明:(1)硝态氮质量浓度为2~8 mg/L时极北海带的相对生长速率和可溶性蛋白含量较高,表明极北海带幼苗适于在此营养盐水平下生长。低氮环境时藻体的丙二醛含量较高,且与相对生长速率呈显著负相关,表明低氮胁迫可引起细胞膜脂过氧化,导致极北海带的相对生长速率降低;(2)在低氮营养盐水平(0~0.5 mg/L)时,藻体超氧阴离子水平明显升高,超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性均升高,表明这3种抗氧化酶尤其是过氧化物酶在清除藻体内自由基时起关键作用,同时丙二醛有较明显的积累,表明在低氮营养盐水平下抗氧化酶的作用可能受到限制。在高氮营养盐水平(10 mg/L)时,藻体超氧阴离子含量较低,且丙二醛无明显积累,3种抗氧化酶活性在高氮环境时均明显升高,表明高氮环境时藻体的抗氧化酶系统发挥作用,清除积累的活性氧。高氮和低氮营养盐胁迫对极北海带幼苗的抗氧化酶系统的影响不同。(3)在高氮和低氮环境时,类胡萝卜素和叶绿素a含量均低于适宜的氮含量条件时的含量,表明类胡萝卜素和叶绿素a对氮胁迫无明显响应。本试验结果可为极北海带苗种生产及人工养殖提供理论参考。

Effects of Nitrogen Concentration on Growth and Biochemical Characteristics of Young Kelp Laminaria hyperborea Seedlings

Kelp Laminaria hyperborea has great potential for seaweed bed construction and artificial cultivation in China. To clarify the suitable nitrate concentration for the growth of young kelp seedlings and the biochemical responses under nitrogen stress, the relative growth rate and biochemical properties were investigated under different nitrate concentration(0, 0.5, 2, 4, 6, 8, and 10 mg/L). The main results were as follows: (1) the optimum nitrate concentration for growth of young kelp seedling was 2—8 mg/L. The malondialdehyde (MDA) content of young seedlings was higher at low nitrate concentration, and it was negatively interrelated with the relative growth rate (RGR), indicating that the membrane lipid peroxidation may be one of the reasons contributing to the low relative growth rate of young kelp seedlings. (2) At low nitrogen concentration (0—0.5 mg/L),the content of superoxide anion (SA) and the specific activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in young kelp seedlings increased significantly, indicating that these three antioxidant enzymes, especially POD played a key role in action of clearing the free radicals. However, there was a more obvious accumulation of MDA, indicating that the action of antioxidant enzymes may be limited to scavenge the SA. At high nitrogen concentration (10 mg/L), there was no significant accumulation of SA and MDA, and the specific activities of SOD, POD and CAT were increased significantly, indicating that the antioxidant enzyme system of young seedlings can function at high nitrogen concentration and scavenge the accumulated reactive oxygen species. In general, high and low concentrations of nitrate nutrient showed different effects on the antioxidant enzyme system of the young kelp seedlings. (3) In the high and low concentrations of nitrate nutrient and phosphate, carotenoid and chlorophyll-a contents were lower than the appropriate concentration, indicating that it had not respond to nitrogen stress significantly. These findings can provide theoretical guidelines for the seedling, breeding and artificial cultivation of kelp L. hyperborea .