不同生境盐地碱蓬对氮饥饿的响应

为了探讨不同生境盐地碱蓬对低氮生境的适应机制,测定了盐渍环境下(200 mmol/L Na Cl)不同浓度硝态氮(0.3、5 mmol/L NO~-_3-N)预处理两种生境盐地碱蓬经氮饥饿后的NO~-_3含量、硝酸还原酶(NR)活性、光合特性及生长状况。结果表明,0.3和5 mmol/L NO~-_3-N处理以及进行氮饥饿时,潮间带生境盐地碱蓬叶片NO~-_3含量均高于内陆生境盐地碱蓬。与内陆生境盐地碱蓬相比,氮饥饿后,潮间带生境盐地碱蓬叶绿素含量、NR活性和光合放氧速率下降幅度均小于内陆生境盐地碱蓬,在0.3mmol/L NO~-_3-N预处理进行氮饥饿时趋势更加明显。0.3 mmol/L NO~-_3-N预处理后氮饥饿对潮间带生境盐地碱蓬根冠比没有影响,却降低内陆生境盐地碱蓬根冠比。上述结果表明,低氮条件下潮间带生境盐地碱蓬具有较高的NO~-_3储存能力,在环境持续氮素缺乏时具有较高的NO~-_3-N再利用能力,能更好地维持氮代谢以及光合性能。说明潮间带生境盐地碱蓬能更好地适应低氮生境。

Effects of nitrogen starvation on Suaeda salsa from different habitats

Suaeda salsa L. can grow in the intertidal zone, or on inland saline soils. After pretreatment with different concentrations of nitrogen (0.3 and 5 mmol/L NO₃^--N), seedlings of two S. salsa populations were watered with a nitrogen-free nutrient solution (nitrogen starvation) at 200 mmol/L NaCl. After one or two weeks, the chlorophyll content and NO₃^-, nitrate reductase (NR) activity, photosynthetic oxygen evolution rate in leaves, and shoot and root dry weight were measured. With 0.3 or 5 mmol/L NO₃^--N pretreatment, the NO₃^- content in leaves from the intertidal population was higher than from the inland population throughout the whole study. Nitrogen starvation decreased the chlorophyll content, NR activity, and photosynthetic oxygen evolution rate in leaves from the inland population more severely than in the intertidal population leaves. This was especially apparent when seedlings were pretreated with 0.3 mmol/L NO₃^--N. As for S. salsa from inland saline soils, the root/shoot ratio decreased significantly after nitrogen starvation. However, nitrogen starvation had no adverse effects on this ratio for the intertidal population after the pretreatment. The results suggest that S. salsa from the intertidal zone has a higher capacity for NO₃^- storage and nitrogen assimilation under low nitrogen conditions. As a result, the intertidal population seedlings have a higher ability for NO₃^--N reutilization to maintain nitrogen metabolism and normal photosynthesis. This indicates that S. salsa from the intertidal zone can better adapt to low nitrogen habitats as compared to the inland population. These traits may affect the distribution of S. salsa in their natural saline environments.