土壤水分对强筋小麦‘豫麦34’氮素同化酶活性和籽粒品质的影响

 以强筋型小麦(Triticum aestivum)品种‘豫麦34号’为材料,采用盆栽方法研究了土壤水分对氮素同化酶活性及籽粒品质的影响。结果表明：旗叶硝酸还原酶（NR）活性于花后呈下降趋势,且土壤含水量为田间持水量（FC）60%的处理活性最强,其次为40%FC,活性最低的是80%FC。旗叶和籽粒中谷氨酰胺合成酶（GS）活性于开花15 d前均呈下降趋势,15 d后均为上升趋势,各水分处理间酶活性大小关系是：80%FC＞60%FC＞40%FC。各水分处理间旗叶和籽粒谷氨酸合成酶（GOGAT）活性的大小关系同GS。60%FC籽粒产量及品质最优,80%FC产量次之,40%FC产量最低;40%FC品质次之,80%FC品质最低。不同水分处理下籽粒蛋白质含量与叶片NR、GS 和籽粒GOGAT活性均呈正相关,与旗叶GOGAT活性呈负相关。且40%FC和80%FC下籽粒蛋白质含量只与旗叶GS活性相关性达显著水平, 60%FC下蛋白质含量则与旗叶NR和籽粒GS活性均达显著相关,与旗叶GS活性达极显著相关。     

氮素形态对不同专用型小麦根系及氮素利用率影响的研究

采用盆栽方法研究了3种氮素形态对不同专用型小麦根系及氮素利用率的影响．结果表明,拔节期以后,强筋型小麦豫麦34在酰胺态氮处理下,根系生物量、根系活力、氮素利用率、氮收获指数和籽粒蛋白质含量最高,铵态氮处理次之,硝态氮处理最低．中筋型小麦豫麦49的各测定指标以铵态氮处理最高,其它指标在酰胺态氮和铵态氮间的趋势不同;弱筋型小麦豫麦50在酰胺态氮处理下各项指标最高,而铵态氮处理下蛋白质含量最低,符合品种优质和专用,氮收获指数与籽粒蛋白质含量之间呈现极显著正相关。     

氮素形态对专用小麦中后期根际土壤微生物和酶活性的影响

采用盆栽方法研究了酰胺态氮、铵态氮和硝态氮对强筋小麦(Triticum aestivum L.)"豫麦34"、中筋小麦"豫麦49"和弱筋小麦"豫麦50"生育中后期根际微生物和土壤酶活性的影响.结果表明,专用小麦根际真菌、细菌、放线菌数量和土壤脲酶、蛋白酶、硝酸还原酶活性以及根际pH值对氮素形态的反应不同."豫麦34"施用硝态氮,对根际土壤真菌、细菌(除成熟期外)和放线菌数量均具有明显的促进作用;"豫麦49"施用铵态氮,根际土壤细菌和放线菌数量最大,根际真菌数量在孕穗期和开花期以酰胺态氮处理最大,而成熟期以硝态氮处理最大;"豫麦50"施用硝态氮,对根际土壤真菌、细菌和放线菌数量均具有明显的促进作用.不同专用小麦品种均表现为在酰胺态氮处理下,根际土壤脲酶活性最高;在铵态氮处理下,根际土壤蛋白酶活性最高;在硝态氮处理下,根际土壤硝酸还原酶活性和pH值最高.     

氮素形态对小麦花后不同器官内源激素含量的影响

采用盆栽方法,研究了酰胺态氮、铵态氮和硝态氮对小麦(Triticum aestivum)花后根系、旗叶和籽粒内源激素IAA、GA₃、ABA和ZR含量的影响。结果表明,小麦不同器官的内源激素含量对3种氮素形态的响应不同。氮素形态调节籽粒灌浆是通过根系、旗叶和籽粒中内源激素的协同作用而实现的。酰胺态氮与硝态氮处理相比,小麦花后5~15 d,旗叶GA₃含量、籽粒IAA和ABA含量较高,籽粒灌浆速率(Grain-filling rate, GFR)较高;花后15~25 d,根系GA₃含量、旗叶IAA和GA₃含量、籽粒ABA含量较高,籽粒IAA含量较低,GFR较低。铵态氮与硝态氮处理相比,小麦花后5 d,籽粒ZR含量较高;花后15 d前后,籽粒IAA、ABA含量较低,GFR较低;花后20~25 d,根系ZR、GA₃含量较低,旗叶IAA、GA₃含量较低,ABA含量较高,籽粒ABA、GA₃含量较低,IAA含量较高,GFR较高。铵态氮比硝态氮处理的小麦籽粒粒重显著增加。铵态氮和酰胺态氮处理比硝态氮处理增产显著。建议在‘豫麦49’施肥时,使用铵态氮或酰胺态氮并配施硝化抑制剂。     

不同环境条件下小麦氮代谢关键酶活性及籽粒品质

研究了两种环境条件下3个不同蛋白含量小麦品种的氮代谢关键酶活性及籽粒品质的差异.结果表明,龙口试验点的小麦旗叶硝酸还原酶(NR)、谷胺酰氨合成酶(GS)和籽粒谷胺酰氨合成酶活性均显著高于泰安试验点,3个品种间的酶活性顺序均为：济麦20＞优麦3号＞PH971942.优质强筋小麦品种的籽粒综合品质性状在龙口试验点的表现优于泰安试验点. 灌浆期环境因素与小麦籽粒品质和酶活性存在显著的相关性,灌浆期间的较高气温、适当干旱和寡照环境有利于提高小麦籽粒品质.龙口试验点的中、强筋小麦品种和泰安试验点的中筋小麦品种蛋白质含量与旗叶NR和GS活性均达显著正相关.小麦品种用途不同,对环境条件的要求不同,适宜的环境条件提高了氮代谢关键酶的活性,利于改善小麦品质.     

氮素水平对花生氮素代谢及相关酶活性的影响

 在大田高产条件下研究了氮素水平对花生(Arachis hypogaea)可溶性蛋白质、游离氨基酸含量及氮代谢相关酶活性的影响, 结果表明, 适当提高氮素水平既能增加花生各器官中可溶性蛋白质和游离氨基酸的含量, 又能提高硝酸还原酶、谷氨酰胺合成酶和谷氨酸脱氢酶等氮素同化酶的活性, 使其达到同步增加; 氮素水平过高虽能提高硝酸还原酶和籽仁蛋白质含量, 但谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH)的活性下降; N素施肥水平不改变花生植株各器官中可溶性蛋白质、游离氨基酸含量以及硝酸还原酶(NR)、谷氨酰胺合成酶、谷氨酸脱氢酶活性的变化趋势, 但适量施N (A2和A3处理)使花生各营养器官中GS、GDH活性提高; 氮素水平对花生各叶片和籽仁中GS、GDH活性的高低影响较大, 但对茎和根中GDH活性大小的影响较小。     

开花后小黑麦旗叶氮代谢与籽粒蛋白质形成的品种间差异

为了解不同类型小黑麦(×Triticosecale)氮代谢及籽粒蛋白质形成的差异,本文以加工型品种‘东农8809’、饲用型品种‘东农5305’和粮饲兼用型品种‘东农96026’为材料,采用随机区组设计,探究3个类型小黑麦品种氮同化、氮素积累及转运、蛋白质积累特性的变化。结果表明,加工型品种‘东农8809’花后氮素同化量高而氮素转运量低,籽粒蛋白质主要来源于花后植株的同化吸收;饲用型品种‘东农5305’硝酸还原酶(NR)和谷氨酰胺合成酶(GS)活性高,旗叶可溶性蛋白含量和游离氨基酸含量较高,对氮的贮存能力高,利于生育后期向籽粒转运;粮饲兼用型品种‘东农96026’的NR和GS活性较低,且生育后期GS降幅大,氮同化能力较低,氮素转运量和氮转运效率小,氮素转运能力弱。     

氮、钾水平对小麦籽粒蛋白质合成关键酶活性的影响

在大田栽培条件下,以蛋白质含量差异的两个冬小麦(Triticum aestivum L.)品种宁麦9号(低蛋白)和扬麦10号(中蛋白)为材料,研究了不同氮、钾施肥水平对小麦旗叶与籽粒中游离氨基酸含量、蛋白质合成关键酶活性和籽粒蛋白质含量的影响及其与开花期旗叶氮、钾营养的关系.结果表明,氮、钾施肥显著提高了小麦花后旗叶与籽粒中游离氨基酸和籽粒蛋白质含量、旗叶谷氨酰胺合成酶(GS)及籽粒GS和谷丙转氨酶(GPT)活性,其中氮肥的作用大于钾肥、氮钾肥配合达到最大,对扬麦10号的效应大于宁麦9号.开花期旗叶氮/钾比随施氮水平的增加呈二次曲线变化,随施钾水平的增加呈下降趋势.旗叶GS活性和成熟期籽粒蛋白质含量与氮/钾比均呈显著或极显著的二次曲线关系.因此,旗叶和籽粒中蛋白质合成关键酶活性受开花期旗叶氮/钾比的显著影响,是氮、钾素影响小麦籽粒蛋白质形成的重要生理原因.     

外源钙离子对小麦幼苗氮素代谢的影响

以普通小麦豫麦34为材料,研究了不同浓度的外源Ca2 对小麦幼苗氮素代谢的影响.在小麦第一片叶完全展开后,开始外源Ca2 处理,设0 (对照)、2、4 mmol · L-1 和8 mmol · L-1 4个Ca2 浓度梯度.处理5d后,测定氮同化酶活性、氮同化量及其它相关代谢物含量.结果表明,小麦幼苗叶片中硝酸还原酶(NR)和谷氨酰胺合成酶(GS)在2 mmol · L-1 Ca2 处理下活性比对照有显著增加,4 mmol · L-1 Ca2 处理的NR活性增加明显,但GS活性增加不显著;8 mmol · L-1 Ca2 处理下NR和GS活性比对照均明显降低.谷氨酸脱氢酶(NADH-GDH)活性在2 mmol · L-1 Ca2 处理下活性增加不明显,而在4、8 mmol · L-1 Ca2 处理下活性显著增加.小麦幼苗氮同化量以4 mmol · L-1处理最大,2 mmol · L-1处理与4 mmol · L-1之间差异不显著;Ca2 浓度为8 mmol · L-1时,氮素同化量明显降低.结果揭示了小麦幼苗不同氮同化途径对Ca2 的响应不同,GS途径比GDH途径对小麦氮素同化量的增加作用更大;4 mmol · L-1对小麦幼苗的氮素利用可能是最有效的Ca2 浓度.     

高蛋白和低蛋白型小麦花后氮素的同化特性

为了解小麦花后介质氮素输入籽粒的同化途径,在不同发育时期不同施氮水平下,采用GS抑制剂(草丁膦)和15N示踪结合,研究了高低籽粒蛋白两种类型品种花后介质氮素的同化特征.结果表明,叶片GS抑制剂处理使豫麦47穗中的NDFF(氮含量中来自介质N的百分比)显著升高,豫麦50则显著降低;穗部GS抑制剂处理使豫麦47叶中的NDFF上升,而豫麦50(开花期)低氮处理上升、高氮处理下降.花后豫麦47的介质N同化量远大于豫麦50,同化介质N的主要器官为根茎,根茎∶叶∶穗的花后介质氮同化量之比约为4∶1∶2;而豫麦50的主要同化器官则为叶片,根茎∶叶∶穗之比约为1∶5∶1.随施N量的增加,豫麦47叶片花后介质N同化量增加,豫麦50则减少;且豫麦47叶片花后同化介质N的输出量显著小于籽粒花后介质N的同化量,而豫麦50叶片花后介质氮的输出量显著大于籽粒介质N的同化量.说明不同类型小麦品种花后N素由根系到籽粒的代谢同化途径具有显著差异,高蛋白品种豫麦47花后由根系流向籽粒的氮素可以不经叶片直接到达籽粒,低蛋白品种豫麦50则必须经过叶片才能到达籽粒.     

Alterations in nitrogen assimilation and partitioning in nitrogen stressed plants

Although nutrient stress is known to alter partitioning between shoots and roots, the physiological basis for the phenomenon is unresolved. Experiments were conducted to examine assimilation of ¹⁵NO₃ by N-stressed plants and to determine whether apparent changes in assimilation in the root contributed to alterations in whole-plant partitioning of reduced-N. Tobacco plants (Nicotiana tabacum L. cv. NC 2326) were exposed to a low concentration of NO₃^? in solution (80 μM) for 9 days to effect a N-stress response. Exposure of plants to 1000 μM¹⁵NO₃^? for 12 h on selected days revealed that roots of N-stressed plants developed an increased capacity to absorb NO₃^?, and accumulation of reduced-¹⁵N in the root increased to an even greater extent. When plants were exposed to 80 or 1000 μM¹⁵NO₃^? in steady-state, ¹⁵NO₃^? uptake over a 12 h period was noticeably restricted at the lower concentration, but a larger proportion of the absorbed ¹⁵N still accumulated as reduced-¹⁵N in the root. The alteration in reduced-¹⁵N partitioning was maintained in N-stressed plants during the subsequent 3-day “chase” period when formation of insoluble reduced-¹⁵N in the root was quantitatively related to the disappearance of ¹⁵NO₃^? and soluble reduced-¹⁵N. The results indicate that increased assimilation of absorbed NO₃^?, in the root may contribute significantly to the altered reduced-N partitioning which occurs in N-stressed plants.     

Carbon and nitrogen stoichiometry and nitrogen cycling rates in streams

Stoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH₄⁺ uptake rates were measured in eight streams using short-term ¹⁵N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams.     

土壤微生物生物量氮及其在氮素循环中作用

简述了土壤微生物生物量氮的含量及其影响因素,阐述了其在土壤氮素循环中的重要作用,着重讨论了其与可矿化氮、矿质氮、有机氮和固定态铵之间的关系,指出土壤微生物生物量氮与供氮因子间的关系在氮素循环研究中有非常重要的作用,可为调控土壤氮素的供应状况,减少氮素损失,提高氮肥利用率提供科学依据,并提出了需要深入研究的问题。     

Vertical leaf nitrogen distribution in relation to nitrogen status in grassland plants

Vertical gradients of leaf nitrogen (N) per unit leaf area (NLA) are viewed as plastic responses that optimize N utilization with respect to carbon assimilation. However, it has been shown that plant species, sowing density and N availability affect the steepness of the NLA gradient relative to the photon flux density (PFD) gradient. This paper tests the hypothesis that such variation is related to the N status of the plant. The N status was analysed using the concept of the critical N concentration (Ncrit) in which shoot N per unit dry mass (NSM) decreases with shoot mass, and a negative deviation of actual NSM from Ncrit indicates N shortage in the plant. The hypothesis was tested with contrasting grassland species Medicago sativa, Dactylis glomerata and Taraxacum officinale by varying PFD and N availability, plant density and hierarchical positions of individuals within stands. Combinations of all treatments showed a general negative correlation between the N allocation coefficient (i.e. the slope of the NLA-PFD relationship) and NSM for all three species. Thus, NLA, relative to PFD, gradients became steeper with increasing shoot mass and increasing N shortage in the plant. These data are consistent with the view that internal N availability is an important factor in modifying the NLA gradient.     

氮肥运筹对稻茬冬小麦土壤无机氮时空分布及氮肥利用的影响

以宁麦9号和豫麦34号为材料,研究了氮肥基追比对土壤无机氮时空变化、氮素表观盈亏和氮肥利用率的影响。结果表明,施用基肥提高了越冬期0-60 cm土层NO3--N和NH4+-N含量,拔节期追肥对孕穗期各土层无机氮含量无显著影响,追施孕穗肥显著提高了开花期0-60 cm土层硝态氮含量和0-20 cm土层铵态氮含量。不施氮处理各生育阶段均表现为氮素亏缺,施氮处理氮素盈亏呈明显的阶段性,播种至孕穗阶段出现氮素盈余,孕穗至成熟阶段出现氮素亏缺;全生育期氮素表观盈余量两品种平均以5∶5处理最低,7∶3处理最高。两品种氮肥农学效率、氮肥表观回收率和产量均随基肥比例的增加呈先增后降的趋势,均以5∶5处理最高。因此,在小麦生产中应适当减少基施氮肥用量,在小麦拔节孕穗期适当增加追肥比例有利于提高产量和氮肥利用效率,并降低土壤氮素损失。     

Total soil nitrogen and nitrogen mineralization

Summary The mineralization capacity of 24 different soils was determined from incubation experiments. Relatively rapid mineralization and nitrification was found with soils from cultivated land, and pastures, but soils under natural vegetative covers of conifers and hardwoods were mostly ammonifying. A close relationship could be established between the total nitrogen content of the soil and the amount of mineral nitrogen formed during incubation. Important connections could also be shown between the available nitrogen contents at different times during the incubation period; these suggest that the incubation period can be considerably shortened.     

添加氮素对沙质草地土壤氮素有效性的影响

通过氮素添加(20g.m-2.a-1)试验,研究了科尔沁沙地东南部沙质草地生态系统土壤氮矿化及有效氮的季节变化。对2006年生长季的观测发现,添加氮素显著提高了沙质草地生长季土壤铵态氮、硝态氮、矿质氮的含量以及9月1日至10月15日的净氮矿化速率与硝化速率;添加氮素导致土壤有效氮的季节变异增大,净氮矿化(1.29～11.60mg.kg-1.30d-1)与硝化(-4.15～11.20mg.kg-1.30d-1)速率随时间呈上升趋势,铵态氮含量逐渐降低,硝态氮与矿质氮(6.49～20.66mg.kg-1)含量的变化呈"V"型,最小值出现在生物量生长高峰期的7月中旬。该沙质草地土壤氮的有效性较低,施氮肥可明显提高土壤供氮能力。     

Successional changes in soil nitrogen availability,non-symbiotic nitrogen fixation and carbon/nitrogen ratios in southern Chilean forest ecosystems

Vast areas of southern Chile are now covered by second-growth forests because of fire and logging. To study successional patterns after moderate-intensity, anthropogenic fire disturbance, we assessed differences in soil properties and N fluxes across a chronosequence of seven successional stands (2–130 years old). We examined current predictions of successional theory concerning changes in the N cycle in forest ecosystems. Seasonal fluctuations of net N mineralization (N_min) in surface soil and N availability (N_a; N_a=NH ₄ ⁺ –N+NO ₃ ^– –N) in upper and deep soil horizons were positively correlated with monthly precipitation. In accordance with theoretical predictions, stand age was positively, but weakly related to both N_a (r ²=0.282, P<0.001) and total N (N_tot; r ²=0.192, P<0.01), and negatively related to soil C/N ratios (r ²=0.187, P<0.01) in surface soils. A weak linear increase in soil N_min (upper plus deep soil horizons) was found across the chronosequence (r ²=0.124, P<0.022). N_min occurred at modest rates in early successional stands, suggesting that soil disturbance did not impair microbial processes. The relationship between N fixation (N_fix) in the litter layer and stand age best fitted a quadratic model (r ²=0.228, P<0.01). In contrast to documented successional trends for most temperate, tropical and Mediterranean forests, non-symbiotic N_fix in the litter layer is a steady N input to unpolluted southern temperate forests during mid and late succession, which may compensate for hydrological losses of organic N from old-growth ecosystems.     

Postanthesis remobilisation and losses of nitrogen in wheat in relation to applied nitrogen

A ¹⁵N leaf feeding technique was used to measure the extent of remobilisation and loss of nitrogen (N) that had been accumulated prior to anthesis in wheat plants that received three rates of N fertilizer. Uptake of postanthesis N to the heads was reduced as the quantity of applied N was increased. This reduction of postanthesis N uptake did not affect the quqntity of N in the heads because the loss of preanthesis accumulated N was reduced and the extent of remobilised preanthesis N increased at higher rates of N application. At the lowest rate of N application the increase in ¹⁵N in the heads of fertile shoots arose chiefly from the remobilisation of N in the stem supporting the head. At higher rates of N application this source of N was increasingly supplemented by N remobilised from infertile tillers and roots.