水曲柳苗木根系和叶片氮的分配及对生物量影响

Nitrogen and Biomass Partitioning Pattern in Root and Leaf of Fraxinus mandshurica Seedlings

为研究氮素浓度对水曲柳(Fraxinus mandshurica)苗木根系和叶片内氮的分配以及对苗木生物量的影响,采用温室砂培实验对4个不同氮素浓度处理(1、4、8、16mmol/L)下的一年生水曲柳幼苗在不同生长时期根系、茎干和叶片中氮素浓度及其关系进行测定分析。研究结果显示:氮素供给浓度显著影响苗木根系氮浓度和叶片氮浓度。随供氮水平提高,苗木体内根系和叶片氮浓度都明显提高。在生长初期(6月)和中期(7月和8月),叶片中氮浓度分别高于根系9.40、9.55和4.21mg/g,而在生长末期(9月)叶片中氮浓度低于根系;根系中氮浓度与叶片中氮浓度有密切线性关系,在生长初期和中期,根系氮浓度增加1个单位,叶片氮浓度平均增加1.6个单位,在生长末期相关性减弱;氮有效性增加能够促进根系和地上部分生物量增长,其中根系生物量增加明显高于地上部分。当氮供应不足(氮浓度为1和4mmol/L)时,分配到根系生物量1个单位,则分配到地上部分生物量约为0.28个单位。氮供应充足条件下,线性关系也较弱。说明水曲柳是一个对氮素比较敏感的树种,苗木根系和叶片中的氮浓度与其生物量存在显著的关系。

In order to study the effect of different nitrogen （N） concentration treatments on nitrogen partition and biomass allocation, one-year-old Manchurian ash sand with pot supplied with various concentrations of N （Fraxinus mandzhurica） seedlings were planted in （1, 4, 8, 16 mmol/L N） in greenhouse. The nitrogen concentration in seedling tissue （roots, stem and leaves） and their relationship were determined in different growing phase. The Results showed that N concentration supplied affected nitrogen concentration on roots and leaves significantly. Increasing N concentration supplied significantly increased the N concentration in roots and leaves. In the initial growing phase （June） and middle growing phase （July and August）, N concen- tration in leaves, over 9.40, 9.55 and 4.21 mg/g respectively, is higher than that in roots. While N concentration of leaves is lower than that in roots in latter growing phase （Sept.）. There is a strong linear correlation between root N and leaf N concentrations. In the initial and middle growing phase, when root nitrogen con- centration increase 1 unit, leaf nitrogen concentration were increased about 1.6 units. Whereas the correlation was weaken in latter growing phase. Increasing N availability accelerated the growth of root biomass and aboveground biomass. Among them root biomass growth obviously higher than that of aboveground. When nitrogen is insufficient supplied （1 and 4 mmol/L N）, assigning 1 unit to root biomass can make 0.28 units assigned to aboveground. The correlation is weakened when enough nitrogen supplied. It is proposed that Fraxinus mandshurica is sensitive to nitrogen nutrition. Nitrogen concentration in roots and leaves has notable relationships with root biomass and leave biomass.