Availability of several kinds of nitrogenous compounds for the growth of callus tissues from Daucus Carota L., Datura Stramonium L., Pelargonium Inquinans Ait., and Oryza Sativa L.

Plants frequently accumulate or reserve some organic nitrogenous substances of small molecules, when supplied with inorganic nitrogenous compounds in excess. It is well known that rice plants in the field accumulate asparagine when supplied with ammonium salts in excess. This phenomenon is effectively utilized as a criteria for adequate supply of nitrogen fertilizers in the field (1). Accumulation of asparagine has also been generally recognized among seedlings of various plant species grown with excess ammonium, nitrate or urea (2). With rye grass, glutamine was reported to be accumulated in leaves and sometimes excreted when ammonium sulfate was supplied in excess (3). Arginine is a major free amino acid accumulating in nitrogen fertilized apple trees (4), phosphate-deficient mulberries (5), and potassium deficient rice plants (6). Allantoin is known to be a reserve form of nitrogen in some families of higher plants, notably the Aceraceae, Leguminosae and Boraginaceae (7,8). Thus the form of reserve nitrogen compound differs with different plant species.     

Asparagine test in relation with the nitrogen nutritional status of crop plants III

During the course of the previous studies (1, 2) of this series dynamics of asparagine appearance in crop plants was investigated and it was found that its appearance has, definitely, direct relation with the nitrogen nutritional status of crop plants. It was also clarified that its appearance is initiated, mostly, by the starting of the panicle formation and the resultant breaking down and transportation of complex nitrogenous compounds. The simultaneous study of asparagine and nitrate appearance revealed that the nitrate has no direct relation with the panicle formation and asparagine appearance. In the first experiment on rice, we did not try nitrate test together with the asparagine test. The surface layer (less than 1 cm) of the rice soil, even in the waterlogged condition gets oxidised gradually and nitrogen exists mainly as nitrate. Moreover, there has been some mention that the rice roots possess an oxidative atmosphere (3,4,5) around it and soils having less amount of easily decomposable organic matter or high water percolating capacity do not get completely reduced under waterlogging, it is supposed that nitrate which is by nitrification from ammonia may appear specially around the roots. It seemed necessary to include nitrate test in this experiment along with the asparagine test. In addition, to study the role of different sources of nitrogen towards the appearance of asparagine, the experiment was designed to have provision of topdressing in the NH⁴, NH⁴+NO³, NO³ and urea forms. It is expected that the result on the topdressing would bring more and more practicality to the asparagine test.     

盐胁迫下氮素形态对油菜和水稻幼苗离子运输和分布的影响

【目的】土壤盐碱化是制约农作物产量的主要因素之一,盐胁迫影响养分运输和分布,造成植物营养失衡,导致作物发育迟缓,植株矮小,严重威胁着我国的粮食生产。在必需营养元素中,氮素是需求量最大的元素,NO-3和NH+4是植物吸收氮素的两种离子形态。植物对盐胁迫的响应受到不同形态氮素的调控,研究不同形态氮素营养下植物的耐盐机制对提高植物耐盐性及产量具有重要的意义。【方法】本文以喜硝植物油菜(Brassica napus L.)和喜铵植物水稻(Oryza sativa L.)为试验材料,采用室内营养液培养方法,研究了NO-3和NH+4对Na Cl胁迫下油菜及水稻苗期生长状况、对Na+运输和积累的影响,以对照与盐胁迫植株生物量之差与Na+积累量之差的比值,评估Na+对植株的伤害程度。【结果】1)在非盐胁迫条件下,硝态氮营养显著促进油菜和水稻根系的生长;盐胁迫条件下,油菜和水稻生物量均显著受到抑制,Na Cl对供应铵态氮营养植株的抑制更为显著。2)盐胁迫条件下,两种供氮形态下,油菜和水稻植株Na+含量均显著增加,硝态氮营养油菜叶柄Na+显著高于铵态氮营养,叶柄Na+含量/叶片Na+含量大于铵营养油菜,硝态氮营养水稻根系Na+含量显著低于铵营养,地上部则相反。3)铵营养油菜和水稻Na+伤害度显著高于硝营养植株。4)盐胁迫条件下,硝态氮营养油菜地上部和水稻根系K+含量均显著高于铵态氮营养。5)盐胁迫条件下,硝营养油菜和水稻木质部Na+浓度,韧皮部Na+和K+浓度及水稻木质部K+浓度均高于铵营养植株。【结论】与铵营养相比,硝营养油菜和水稻具有更好的耐盐性。硝态氮处理油菜叶柄Na+显著高于铵态氮处理,能够截留Na+向叶片运输。同时,供应硝态氮营养更有利于油菜和水稻吸收K+,有助于维持植物体内离子平衡。盐胁迫下,硝营养油菜和水稻木质部Na+浓度,韧皮部Na+和K+浓度及水稻木质部K+浓度均高于铵营养植株,表明硝态氮营养油菜和水稻木质部-韧皮部对离子有较好的调控能力,是其耐盐性高于铵营养的原因之一。     

几种蔬菜对硝态氮、铵态氮的相对吸收能力

采用溶液培养方法探讨了莴笋、菠菜、小白菜和大青菜 4种蔬菜作物对硝、铵态氮的相对吸收能力以及这两种氮源对它们生长发育的影响。结果表明 ,单独供给NO3-N ,4种作物均生长发育良好 ;供给NO3--N +NH4+-N(NO3-∶NH4+=1∶1) ,生长量均有所下降 ,而单独供给NH4+-N时 ,生长量则大幅度下降。莴笋单独供给NO3--N时 ,其吸氮量显著高于供给NO3--N +NH4+-N的处理 ,大青菜、菠菜供给NO3--N +NH4+-N与单独供给NO3--N相比吸氮量大体相当 ;小白菜同时供应NO3--N +NH4+N时吸氮量最高 ,供给NO3--N时次之 ,供给NH4+-N时显著降低。供给NH4+-N时 4种作物吸氮量均比其它氮源显著降低。 4种作物对NO3--N与NH4+-N的吸收具有明显的偏向性。供给等氮量铵、硝态氮 (NO3--N +NH4+-N处理 )时 ,菠菜、小白菜吸收的NO3-N显著多于NH4+-N ,表现出喜硝性 ,莴笋则与此相反 ,表现出喜铵性 ;而大青菜对两种形态氮素的吸收量相差不多 ,表现出兼性吸收的特点。但上述偏向性具有阶段特点 ,即喜硝作物可能在某一阶段表现出喜铵性状     

Determination of top-dressing for rice in the field by the detection of asparagine

It is well known that an increase of and better grain can be obtained by the application of an adequate amount of quick-acting nitrogen fertilizers such as ammonium sulphate, thirty to twenty five days before heading, and this is a common practice of top-dressing, being called “Hogoe” in Japanese. It is also well known that excess of nitrogen supplied at this time makes plants weak against mechanical injury, insects and disease. For the application of “Hogoe”, therefore, an accurate diagnosis of the nitrogen nutrient condition of rice is required. In a series of investigations on the nitrogen metabolism, the author found that asparagine appeared in parallel with the increase of nitrogen concentration in rice plants, and considered that the detection of asparagine would be a good indicator for assessing the nitrogen requirement of rice lantst^l).     

Response of Lowland and Aerobic Rice to Ammonium and Nitrate Supply During Early Growth Stages

Decreasing fresh water availability has intensified the search for alternative rice cultivation systems with reduced water input, but most evidence suggests negative effects on growth of lowland (LL) rice cultivars. Yield in such production systems may be improved by selection of adapted aerobic ‘Han Dao’ (HD) rice cultivars. Lowland and HD rice were compared under sole nitrate or ammonium supply as well as under mixed supply of both nitrogen (N) forms during the seedling and tillering stage; pronounced differences were found in response to the supplied N form. Shoot dry mass (DM) of HD was significantly lower than that of LL under sole and predominant ammonium supply, whereas LL showed the opposite trend, with significantly lower shoot DM under sole-nitrate supply. Nitrogen concentration of LL rice under sole-nitrate supply was significantly lower compared with other treatments at tillering stage. Han Dao rice had a significantly higher potassium (K) concentration than LL rice under sole-nitrate supply, while the opposite result was observed under sole-ammonium supply. At seedling stage, the portion of N that was taken up from nitrate-N varied from 30% to 40% in HD and LL rice in treatments 75N/25A and 50N/50A, while at both growth stages, predominant ammonium supply resulted in a lower portion (20%) of nitrate-derived N in LL than in HD rice. The portion of nitrate-derived N increased at tillering stage (from 40% to 70%). These results further illustrate a synergistic effect of co-provision of nitrate and ammonium on total N fluxes compared with supply of sole nitrate or sole ammonium. It was concluded that the interaction between N form and tiller formation during early growth stages deserves strong attention for the identification of aerobic rice cultivars.     

不同供氮形态下油菜幼苗对盐胁迫的响应

为比较不同供氮形态下油菜对盐胁迫的响应,通过供应铵态氮和硝态氮,探讨盐胁迫对油菜幼苗生物量、 光合作用、 离子含量等的效应。结果表明: 非盐胁迫条件下的硝态氮处理的植株生物量和叶片光合参数均显著高于其它处理; 在盐胁迫条件下,两种供氮形态处理油菜的生长和光合均受到明显抑制,其中铵态氮处理表现的抑制效应较显著,且其光合抑制主要来自气孔限制。在两种供氮条件下,盐胁迫使得植株Na+浓度均显著增加,其中铵态氮处理的叶片和叶柄中Na+浓度的增幅大于硝态氮处理,而其根中Na+浓度则小于硝态氮处理。盐胁迫导致两种供氮形态下整株和叶柄中K+浓度均显著降低,而在根中,则只造成硝态氮处理的K+浓度的显著降低。在整株水平上,盐胁迫下铵态氮处理的K+ 、 Na+的选择性比率（SK,Na）要显著低于硝态氮处理。综上,在盐胁迫条件下,硝态氮处理对K+吸收维持较高的相对选择性是其耐盐性高于铵态氮处理的重要原因。     

Asparagine test in relation with the nitrogen nutritional status of crop plants: V

The previous (1) investigation on this crop brought two very interesting results which include the presence of nitrate in detectable quantity under waterlogged soil condition and quite different role of different forms of nitrogen towards the appearance of asparagine. It created a new interest in the Asparagine Test study and it was considered essential to obtain confirmatory results with the present investigation. However, the plan of the experiment previously adopted was modified to some extent to get, in addition, informations on the results obtained in the previous investigation. The experiment was aimed to include a completely reduced condition in combination with ammonium and nitrate nitrogen as basal application. Also, urea was excluded from the topdressing forms of nitrogen and only nitrate and ammonium form nitrogens were studied in greater detail.     

Formation of asparagine from 14C-labelled aspartate in different parts of rice plant at the panicle formation stage

Dynamics of asparagine formation and appearance have previously been studied, but it was particularly considered necessary to study the mode of asparagine formation in different parts of rice plant at the stage of panicle formation using ¹⁴C-labelled aspartate. During this investigation the place and velocity of asparagine were studied.     

氮饥饿水稻利用不同形态氮素的差异及其生理机制

通过水培试验，研究了氮饥饿7d后，恢复供应不同形态氮源对水稻氮吸收和积累及氮同化中关键酶活性和光合色素的影响。结果表明，缺氮促进根系生长，增加根冠比。恢复供氮4d显著增加地上部生物量。铵硝混合营养促进了水稻对氮的吸收和转运，叶片和根系中全氮及叶片中铵态氮的含量以硝酸铵处理最高。与单一铵或硝营养相比，铵硝混合营养增强了根系的谷氨酰胺合成酶和叶片中硝酸还原酶的活性，提高了水稻同化和利用氮的能力。另外，与纯硝营养相比，供应铵态氮显著增加了叶片中总叶绿素，尤其是叶绿素a的含量。因此，改善水肥管理、平衡对水稻供氮的铵硝配比将提高水稻氮素的吸收和利用效率。     

不同覆盖旱作水稻对后茬大麦生长和土壤氮素的影响

通过田间试验研究水稻不同覆盖旱作栽培方式对后茬大麦生长及土壤氮素动态变化的影响。结果表明，盖草处理后茬大麦表层土壤硝态氮含量最高，而土壤铵态氮含量由高到低依次为：水作〉盖草〉覆膜〉裸露，且硝态氮、铵态氮从表层（0～20cm）到底层（60～80cm）依次降低。具有明显的层次性。各处理都表现出0～40cm土层氮素表观盈余，水作、盖草和裸露处理后茬分别比覆膜处理后茬高40．5％，39．5％和36．1％。大麦籽粒产量以盖草处理后茬摄高，分别比水作后茬和裸露后茬增加837kg／hm^2和251kg／hm^2。后茬大麦各生育阶段对氮素的累积吸收量均以前茬盖草早作处理最高。覆膜、盖草和裸露旱作水稻后茬大麦的氮肥利用率分别比水作稻后茬大麦高16．1％，17．5％和13．8％。土壤氮素转化和大麦产量均表明，半腐解秸秆覆盖旱作水稻-大麦轮作是一种较合理的种植模式。     

Nitrate reduction and denitrification in flooded soils

It has been well known that the utilization rate of ammonium sulfate fertilizer by lowland rice was as low as 40 percent of the applied ammonium. This low utilization rate was due to nitrogen loss from the paddy field. There are problems as to whether the loss of nitrogen from the flooded soil was caused by the nitrification of ammonium nitrogen and its subsequent denitrification, by the evaporation of ammonium, or by the leaching of ammonium-nitrogen with percolated water. Shioiri and his associatesll clarified that this loss of nitrogen resulted largely from denitrification through nitrate reduction in 1942. After the paddy soil is flooded with water, the oxygen in furrow slice is consumed by aerobic microorganisms, and then the soil becomes reductive. Conversely the oxigen is supplied to the soil through the water from the air, and from various kinds of algae and duckweeds, which produce oxygen through photosynthesis. At the early stage the reduction by oxygen consumption is superior to the oxidation by oxygen supply, the furrow slice is reductive, and is bluish gray in color due to the presence of certain ferrous compounds. After months flooding, the oxygen supply becomes superior to oxygen consumption and the uppermost layer of furrow slice becomes brown in color due to the presence of ferric compounds. This layer corresponds to an “oxidised layer” where microorganisms live aerobically. In this oxidized layer the nitrifying bacteria converts ammonium nitrogen into nitrate nitrogen which is percolated into the reduced layer, and lost through denitrification. A large amount of ammonium sulfate fertilizer is then dressed at the uppermost layer, after flooding, the loss of nitrogen through denitrification is serious.     

环境温度和CO2浓度升高对湖北早稻氮素含量及产量的影响

采用改进后的开顶式气室（OTC）,大田原位模拟温度升高2℃和CO₂浓度增加60μL·L^-1的未来气候情景,观测其对湖北地区早稻植株全氮、土壤氮素及产量的影响。试验设置对照(CK)、增温（增2℃,IT）、增CO2 (增60μL·L^-1,IC)以及增温+CO^₂（增2℃+增60μL·L^-1,IT+IC）4个处理,3次重复,随机区组排列,对早稻各生育期植株全氮含量、土壤NH4⁺-N和NO₃--N含量以及产量构成进行监测。结果表明：（1）温度和CO^₂浓度升高以及二者同增会增加早稻生育早期（特别是分蘖期）植株体内全氮含量,分蘖期以后各处理间差异不显著,籽粒全氮含量差异亦不显著;土壤NH4⁺-N含量与植株全氮变化规律类似,在早稻生育早期,温度和CO^₂浓度升高以及二者同增会增加土壤NH4⁺-N含量,分蘖期以后各处理间差异不显著;（2）温度升高使拔节期、成熟期土壤NO₃--N含量降低,抽穗期土壤NO₃--N含量增加;CO₂浓度增加会提高拔节期、成熟期,降低抽穗期土壤NO₃-N含量;（3）CO₂浓度升高,早稻增产13.4%,与CK差异极显著（P<0.01）,而单独增温或增温+增CO₂处理早稻产量与CK差异不显著。     

根系高效铵吸收系统是玉米获取氮素的重要补充机制

【目的】本研究旨在通过对植株根系铵吸收特征研究,揭示旱地玉米的氮素营养特征,研究结果为玉米补充氮素营养提供了一定的理论依据。 【方法】以玉米高产品种“郑单 958”为供试材料,采用水培试验模拟了玉米植株生长中的氮素营养环境,研究了玉米幼苗生长对不同氮素形态的反应;采用非损伤微测技术 (NMT),重点研究了不同供氮状况下玉米根系对 NH₄+ 的吸收特征,并与其吸收硝态氮的规律进行了比较;利用实时定量 PCR 技术,初步揭示了玉米根系中的铵吸收蛋白 (AMT) 基因对铵的响应特征。 【结果】单一供应铵态氮条件下,玉米地上部鲜重、全株干重及根系含氮量与纯硝态氮条件下相近,表明铵态氮也可作为玉米的有效氮源。非损伤微测研究结果表明,玉米幼苗根系铵吸收过程呈典型的高亲和吸收特征 (表观 Km 值约为 60 μmol/L),推测这一过程是由高亲和的转运体蛋白介导。氮饥饿预处理使根系的铵吸收速率 Vmax 和 Km 值分别降低了约 3 倍和 1 倍。这一现象与水稻等作物不同,暗示玉米的铵吸收过程可能不存在反馈抑制现象。另外,介质中硝态氮的存在对根系的铵吸收具有显著抑制作用 (抑制效果 > 20%);在供试微摩尔浓度范围内,根系对 NO₃– (100 μmol/L) 的吸收速率显著低于对相同浓度 NH₄+ 的吸收。进一步对主要在玉米根系中表达的铵吸收蛋白基因 ZmAMT1;1a 和 ZmAMT1;3 的定量 PCR 分析表明,上述基因在维持供铵状态下的表达量较缺氮处理均有显著提高,与铵吸收测定结果相符。 【结论】玉米根系中保留着高效铵吸收系统,在低硝态氮浓度下,该系统对铵态氮的高效吸收可作为其获取足够氮源的一个重要的机制。高硝态氮则抑制玉米根系对铵态氮的吸收,以避免氮素吸收利用系统在功能上的冗余。     

Effects of a nitrification inhibitor on efficiency of nitrogen utilization by wheat and millet

Abstract

Preliminary soil incubation studies established that the nitrification inhibitor, Dicyandiamide (DCD), could maintain the ratio of NH.‐N to NO₃‐N at predetermined levels. When one part DCD was mixed with 10 parts of the ammonium fertilizer prior to incorporation with the soil, nitrification was inhibited for at least six weeks. In a greenhouse experiment, wheat was grown to maturity and millet to the flowering stage in pots containing nitrate and ammonium fertilizers treated with DCD. Soil analyses during the plant growth period indicated that ammonium oxidation in soil was effectively inhibited. Plants of both species exposed to ammonium only with DCD produced lower yields than those exposed to a mixture of nitrate and ammonium nitrogen with DCD. Plants supplied with nitrate‐only gave somewhat lower yields than the mixtures. The nitrate‐only treatments resulted in the lowest accumulation of reduced nitrogen compounds in shoots of both species. Magnesium uptake by millet and calcium and magnesium uptake by wheat were reduced as the proportion of ammonium in soil was increased.     

玉米?水稻轮作和水稻连作土壤根际和非根际氮含量及酶活性

【目的】以水稻连作为对照,研究玉米?水稻水旱轮作模式对稻田作物根际和非根际土壤氮素含量及酶活性的影响,为稻田系统玉米?水稻轮作对土壤氮素转化与稻田土壤质量的影响提供科学依据。【方法】利用根际袋盆栽试验进行水稻连作与玉米?水稻轮作,在玉米喇叭口期、抽穗期及成熟期,水稻分蘖期、孕穗期及成熟期分别采取根际与非根际土样,测定土壤铵态氮、硝态氮、全氮含量与脲酶、硝酸还原酶活性变化。【结果】两种种植模式及作物生育期对土壤氮素含量和酶活性均有显著影响。不同种植模式下土壤酶活性变化趋势基本相同。与水稻连作相比,玉米?水稻轮作土壤铵态氮减少了24.7%;土壤硝态氮含量增加了153.4%,主要表现在第一季。与水稻连作相比,玉米?水稻轮作条件下两季作物成熟期土壤全氮含量降低,土壤脲酶活性整体提高24.3%,土壤硝酸还原酶活性整体降低34.6%。水旱轮作对各个指标的影响可持续到第二季。根际土壤铵态氮含量及脲酶活性整体低于非根际土壤,玉米根际土壤硝态氮含量低于非根际,水稻根际土壤硝态氮含量高于非根际土壤,根际土壤硝酸还原酶活性高于非根际土壤。【结论】在本试验中,轮作在第一季对土壤氮素及酶活性的影响可持续至第二季。与水稻连作相比,玉米?水稻轮作可以提高作物根际与非根际土壤的脲酶活性及硝态氮含量,有利于氮素有效性的提高。     

The influence of nitrogen fertilisation on bacterial activity in the rhizosphere of barley

The effect of nitrogen addition on the activity of rhizosphere bacteria was studied using barley seedlings. Three different nitrogen sources were added to the soil (nitrate, ammonium and ammonium+nitrate) at four different concentrations (0, 100, 300 and 500 mg N kg⁻¹ soil) and the plants were allowed to grow for 6 weeks. The bacterial activity was estimated by measuring thymidine and leucine incorporation into bacteria extracted using homogenisation-centrifugation. Bulk soil bacterial activity was low compared with that of rhizosphere bacteria. Nitrogen addition did not affect the activity of the bulk soil bacteria, indicating that the activity was not nitrogen limited. The thymidine and leucine incorporation rates of rhizosphere bacteria decreased when ammonium or ammonium+nitrate was applied compared with the non-amended controls. No effect on bacterial activity was found following nitrate addition. There was a significant positive correlation between rhizosphere bacterial activity and rhizosphere pH. Shoot length following ammonium treatment was significant lower than in the non-amended control, while nitrate and ammonium+nitrate addition had no effect. This indicates that the varying effects due to nitrogen sources on rhizosphere bacterial activity were not due to effects on plant growth.     

Alleviating soil sickness caused by aerobic monocropping: Responses of aerobic rice to various nitrogen sources

Yield decline resulting from continuous cropping of aerobic rice is a constraint to the widespread adoption of aerobic rice technology. Shifts in water management from flooded to aerobic conditions are known to influence the availability and form of N present in the soil and might require a different approach to N management in aerobic rice. The present study was conducted to determine the effects of different N sources on the plant growth and grain yield of aerobic rice. Four pot experiments were conducted in which rice was aerobically grown in soil that was taken from fields where aerobic rice has been cultivated for 11 consecutive seasons and an adjacent field where flooded rice has been grown continuously. Nitrogen was applied as ammonium sulfate, urea, ammonium chloride, ammonium nitrate and potassium nitrate at four N rates of 0.3, 0.6, 0.9 and 1.2 g N pot⁻¹. Two unfertilized controls consisting of soil that was either untreated or oven heated at 120°C for 12 h were also included. Plants were sampled during the vegetative stage or at maturity to measure plant growth, N uptake, grain yield and the yield components. Growth of aerobic rice in aerobic soil was generally better with the application of ammonium-N than nitrate-N. Potassium nitrate decreased plant growth and caused plant death at the high N rate. Ammonium sulfate was more effective in improving the vegetative plant growth, N nutrition and grain yield of aerobic rice than urea at the high N rates. The application of ammonium sulfate achieved the same and even better plant growth than the soil oven-heating treatment. These results suggest that there is a possibility of reversing the yield decline observed in the continuous aerobic rice system by using the right source of N fertilizer at the optimal rate.     

The uptake,distribution, and accumulation of 15N-labelled ammonium and nitrate nitrogen top-dressed at different growth stages of rice

A pot experiment with soil culture was carried out to trace ¹⁵N-labelled nitrogen top-dressed at different growth stages of rice. The study involves the use of a modified vacuum system for determining total nitrogen by gu volumetric measurement, and the N₂ gas sampled in the discharge tube was analysed for nitrogen-15 by the optical spectrographic technique.

The plants took up more nitrogen from (¹⁵NH₄)₂SO₄ than from Na¹⁵NO₃, irrespective of the stage of dressing, and the uptake of both forms was much higher when the planta were top-dressed at the young panicle formation stage as compared with the later dressings. At full maturity the plants had the highest accumulation of labelled nitrogen from both ammonium and nitrate sources when they are top-dressed at the young panicle formation stage. More than 80% ot the labelled nitrogen taken up by the plants waa distributed in the brown rice and this trend was more remarkable when top-dressing was carried out at the milk stage. The distribution patterns of ammonium and nitrate nitrogen were similar in brown rice but differed in leaves and stem.

Nitrogen transported from other parts to the panicle was utilized for the formation ot the husk until the booting stage, and then for brown rice development. With the completeness of husk formation, at the milk stage, nitrogen transported to the grain might have been utilized for brown rice development more rapidly. In the brown rice, nitrogen from ammonium was translocated maximally to the inner part of the endosperm from dressing at the booting stage, and to the embryo from that at the milk stage, whereas that from nitrate was translocated maximally to the embryo from the dressings at both stages.     

水稻根系形态与氮素吸收累积的相关性分析

【目的】氮肥过量施用,不仅造成氮肥大量流失,还增加了农业生产成本,对生态环境带来了巨大的威胁。水稻根系形态作为影响养分吸收和利用的主要因素之一,明确其与氮素吸收累积的相关性是提高氮素利用效率、降低环境污染的有效途径。【方法】利用营养液培养方法,研究了 55 个水稻品种在 NH₄+-N 和 NO₃–-N 供应条件下苗期植株生物量、氮含量和氮素累积量及其与根系形态指标的相关性。【结果】在 NH₄+-N 培养下,水稻营养指标与根系形态指标的相关性高于其在 NO₃–-N 培养下的相关性。在相同供氮水平下,供应 NH₄+-N 的水稻苗期平均生物量为 55.77 mg/plant,比供应 NO₃–-N 的量高 4.94 mg/plant;水稻苗期平均氮含量为 4.22%,比供应 NO₃–-N 的高 0.72%;水稻苗期平均氮累积量为 1.91 mg/plant,比供应 NO₃–-N 的苗期平均氮累积量高 0.67 mg/plant。在 NH₄+-N 和 NO₃–-N 两种氮素形态培养条件下,水稻根系形态指标品种间根尖数变异系数最大,平均根系直径变异系数最小。总根体积、总根面积、总根长、分枝数四个形态指标与植株生物量、植株氮含量、植株氮累积量相关性最为显著,且相关系数 (r) 呈总根体积 > 总根面积 > 总根长 > 分枝数的规律。在 NH₄+-N 培养下的水稻营养指标与根系形态指标的相关性要高于其在 NO₃–-N 培养下的相关性。【结论】水稻苗期总根体积、总根面积、总根长、分枝数可作为水稻氮高效评价的重要指标。