氮胁迫对水曲柳幼苗养分吸收、利用和生物量分配的影响

树木受到环境胁迫时发生形态和生理上的改变，以便获取对其生长发育限制最严重的资源．在东北林区凋落物因受温度影响分解速度和有机物矿质化过程缓慢，森林树木常受到氮营养胁迫．通过温室栽培试验，对氮胁迫下水曲柳幼苗生长的生理学和形态学指标进行了研究．结果表明，在氮胁迫下，水曲柳幼苗的净氮吸收速率和净磷吸收速率都会减少，但在生长前期氮利用效率和磷利用效率高于氮供给充足(8mmol·L^-1)和过量(16mmol·L^-1)时的氮利用效率和磷利用效率．当氮供给浓度不足时，叶重比减少，而特定叶面积和根重比增加．相对生长速率随氮供给浓度增加而增加．在氮胁迫下净同化速率下降，导致总生物量下降．在幼苗生长前期，水曲柳幼苗处于氮胁迫时根／茎比显著大于氮供给充足或过量时的根／茎比。而在生长后期。根／茎比没有显著差别．

Effects of nitrogen stress on nutrient uptake by Fraxinus mandshurica seedlings and their biomass distribution

Under environmental stresses, trees often change their morphological and physiological components to acquire the most limited resources. In northeastern forest region of China, the decomposition and mineralization of litters occur slowly due to low temperature, which often results in forest trees suffering from nutritional stress. With pot culture in greenhouse, this paper studied the effects of nitrogen stress on the physiological and morphological components of Fraxinus mandshurica seedlings. The results showed that under N stress, the net uptake rate of nitrogen and phosphate by the seedlings decreased, while their nitrogen and phosphate use efficiency were higher than those of the seedlings supplied with 8 mmol x L(-1) or 16 mmol x L(-1) of nitrogen during the early growth stage. When suffering from N stress, the leaf mass ratio of the seedlings reduced, with specific leaf area and root mass ratio increased. The relative growth rate increased with the increasing N concentrations supplied to the seedlings during the whole growth period. Under N stress, the net assimilation rate decreased, which resulted in the decrease of total biomass, and the root/shoot ratio was significantly higher than that of the seedlings supplied with 8 mmol x L(-1) or 16 mmol x L(-1) of nitrogen during the early growth stage. There was no significant difference during the late growth stage.