中文摘要：

采用温室沙培方法,在不同氮浓度处理下,研究1年生水曲柳苗木整株根系和前3级根形态,以及前3级根形态与解剖结构的关系,探讨不同氮浓度导致细根形态变化的原因。结果表明：1）随着氮浓度的增加,整株根系的总面积、总长度和比根长增加,但是总的平均直径减小,前3级根也具有相同的变化规律。根表面积和比根长从低氮到高氮增加与直径和根长的变化有关。2）氮浓度引起直径和根长变化与解剖特征变化有密切关系。低氮条件下直径增加与横切面皮层细胞直径和皮层厚度的增加有关,而高氮条件下皮层细胞直径减小和皮层厚度缩窄有关。在纵切面上,根长度从低氮到高氮增加可能与细胞数量增加有关。研究结果对解释施肥导致细根形态变化原因具有重要意义。

英文摘要：

Fine root morphology can affect root absorption of nutrients and water from soil,and the morphology is not only controlled by root structure,but also by exterior environments. In this paper,root morphology variation of Fraxinus mandshurica seedlings in response to nitrogen concentration was investigated with a potting sand-cultured experiment with three nitrogen （N） level in a greenhouse. The changes of morphology in both total roots and the first three order roots,and anatomical properties under different N concentration treatments were examined respectively. The results showed that： 1） total root surface area,total root length and specific root length （SRL） increased significantly with increasing N supplied,however,mean diameter was higher in low N treatment than in control and high N treatments. These morphological indices in the first three order roots had the same patterns as total roots. The changes in root surface area and SRL of the first three order roots from low N to high N treatments were derived from integrated changes of their diameter and length. 2） The changes of diameter and length in the first three order roots with different N treatments were closely related to changes of their anatomical properties. Increasing cortical cell diameter and cortical thickness in transverse section at low N treatment resulted in larger diameter roots. In contrast,cortical cell diameter and cortical thickness were reduced in high N treatment,therefore,resulting in smaller diameter. In vertical section,root length increment from low N to high N treatments was possibly due to increasing cell numbers at long direction. These results suggested that variations of fine root morphology under different N treatments were closely related to root anatomical changes.