【摘要】 水曲柳 (Fraxinusmandshurica)是我国东北林区重要的工业用材树种 ,在东北林区广泛种植 ,因而其培育近来日益得到高度重视。在水曲柳的种植区域内 ,尽管林地内凋落物丰富 ,但该地区气温低 ,冬季长 ,氮素矿化速度低 ,氮素供给显得不足。本研究采用沙培的方式 ,在为幼苗提供完全平衡营养液 30d后 ,对幼苗进行 4种不同的氮素浓度 (1、4、8、16mmol·L-1)或 5种氮素形态 (NO-3 _N和NH+ 4 _N)比例 (0、2 5 %、5 0 %、75 %、10 0 % )的处理。氮素浓度处理使用NH4NO3 ,氮素形态处理中NO-3 _N使用KNO3 ,NH+ 4 _N使用NH4Cl。每一种处理方式重复 15次。随后对不同的氮浓度和形态比例对水曲柳幼苗的叶绿素合成、光合作用、生物量的累积以及生物量在地下部分和地上部分的分配的影响进行了研究 ,旨在进一步了解氮素浓度和氮素形态的比例对水曲柳幼苗生理生态学的影响。在氮素浓度处理中 ,5_氨基_酮戊酸 (5_aminolevulinicacid ,ALA)的合成速率随氮素浓度呈现不规则变化 ,在 1mmol·L-1处达到最大 (0 .72 μmol·g-1FW·h-1) ,在 4mmol·L-1处最小。当氮素形态比例从 0增加到 5 0 %时 ,ALA合成速率逐渐增加 ,而当氮素形态比例再增加时 (75 %～ 10 0 % ) ,ALA合成速率反而减少。氮素浓度对胆色原素 (Porphobilinogen ,P更多还原

【Abstract】 Fraxinus mandshurica, native to northeastern China, is an important timber tree. The tree often suffers from nitrogen (N) deficiency because long winter results in slow decomposition rate of litter. In the present study, effects of different concentrations and form ratios of nitrogen on chlorophyll biosynthesis, total leaf N, soluble protein, and photosynthesis were studied. During the N concentration treatment, biosynthesis rate of 5_aminolevulinic acid (ALA) and activity of porphobilinogen (PBG) synthase showed irregular changes, but total chlorophyll content increased when N concentrations varied from 1 to 8 mmol·L -1, and activity of PBG synthase did not change significantly. Total leaf N, soluble leaf proteins, and photosynthesis rate also increased when N concentrations increased from 1 to 8 mmol·L -1. These results suggested that N concentrations did not affect biosynthesis rates of ALA and activities of PBG synthase and 8 mmol·L -1 of N most increased total leaf N, soluble proteins in leaves, and photosynthesis rate. During the N form treatment, biosynthesis of ALA increased when the ratio of NO - 3_N increased from 0 to 50%, but activity of PBG synthase, total chlorophyll concentrations, total leaf N and soluble leaf proteins increased when the ratio of NO - 3_N increased from 0 to 75%. Photosynthesis rate also increased when the ratio of NO - 3_N increased from 0 to 75%. During the two types of treatments, there were significant relationships between total leaf N, soluble protein concentrations and net photosynthesis rates. These results suggested that F. mandshurica seedlings showed a preference for NO - 3_N, but the ratio of 75% NO - 3_N to 25% NH + 4_N promoted an increase in chlorophyll biosynthesis, accumulation of N and soluble proteins in leaves, and net photosynthesis rate. Total biomass increased as exogenous nitrogen concentrations increased from 1 to 8 mmol·L -1. Biomass partitioning to roots decreased, and biomass partitioning to shoots increased. As ratios of NO - 3_N to NH + 4_N increased from 0 to 75%, total biomass increased, but biomass partitioning to roots increased as ratios of NO - 3_N to NH + 4_N increased from 0 to 100%. When both nitrogen concentration treatment and form ratio treatment were carried out, biomass accumulation was closely related to photosynthesis rate, and the relationship between biomass accumulation and photosynthesis was related to nitrogen partitioning in leaves. It is proposed that 8 mmol·L -1 and 75% NO - 3_N∶25%NH + 4_N should be used in practical cultivation of F. mandshurica seedlings.更多还原