Productivity of Maize (Zea mays L.) in Relation to Morphological and Physiological Characteristics under Varying Amounts of Nitrogen Supply

In a field trial located in a northern region of Germany, characterized by a Podzol soil and increasing N fertilization resulted in an enhanced N uptake of the maize (Zea mays L.) variety “Felix” with increasing N fertilization ranging from 0 kg N ha^-1 (N1) to 60 kg N ha^-1 (N2) and to 160 kg N ha^-1 (N3). The growth conditions reached only nearly optimal temperature for biomass allocation in a short period of July and August 1990. The plant productivity was stimulated due to higher N uptake and N utilization to values of nearly 1600 g ha^-1. The N efficiency decreased with increasing N fertilization. A greenhouse experiment was conducted to study the effects of varied nitrogen nutrition on the development of maize plants under standardized growth conditions, comparable to the sub optimal growth conditions of the field experiment. Physiological and anatomical parameters were measured. Within a range of 0.2—1.0 mg N cm^-2 of leaf nitrogen, the chlorophyll concentration and the CO₂ exchange rate showed a linear relationship with the reduced N in the leaf. Above 1.0 mg N cm^-2 no further increases in chlorophyll levels or photosynthesis were observed. Nitrate reductase activity was stimulated throughout the N range supplied. The activities of photosynthetic enzymes (PEP carboxylase, Nadp malic enzyme, RubP carboxylase) was increased from the low (0.19 g N kg^-1 soil) to the middle N level (0.37 g N kg^-1 soil). Under conditions of a high N supply (0.75 g N kg^-1 soil) the activity decreased, except Nadp malic enzyme. This effect was accompanied by alterations of the internal structure of the leaf. Leaf thickness and size of the mesophyll parenchyma were less at the medium nitrate supply. Other anatomical parameters were influenced in proportion to leaf nitrogen status. Stomatal index was not affected by N supply, but lengths and widths of epidermal and stomatal cells as well as the distance between stomata and vascular bundles were increased by high N supply. It is proposed that above an optimal range of leaf nitrogen, maize plants cannot use the potential advantage of the C₄ mechanism and the N utilization shows maximum efficiency in the intermediate N level under the sub optimal growth conditions used in the greenhouse experiment.     

竹醋液对黄瓜生长的影响

以黄瓜为供试作物,探讨竹醋液的不同处理方法对黄瓜生长发育和产量的影响。结果表明,每立方米育苗基质中竹醋液添加量为250～500ml,或苗期用200倍竹醋液灌根,或是在每立方米基质中使用500ml竹醋液处理育苗基质和栽培基质,并在定植后定期用200倍灌根的综合处理方法,能够有效地促进黄瓜叶片、茎粗和株高的生长。竹醋液综合处理可以显著提高黄瓜产量,降低黄瓜中硝酸盐的含量。     

Responses of Root Nodule Formation and Nitrogen Fixation Activity to Nitrate in a Split-Root System in Peanut (Arachis hypogaea L.)

Peanut is an important constituent of crop rotation systems with various vegetable crops, which need large amounts of inorganic nitrogen. Nitrate inhibits nodule formation and nitrogen fixation of the peanut plants in these cropping systems. To elucidate this nitrate-induced inhibition, an experimental method using a split-root system was designed and the inhibitory level of nitrate (14 m M ) was applied to half of the roots for 5 or 30 days in pot experiments. In the application of nitrate for 5 days, the dry weight, the nitrogen content, and both the number and the fresh weight of nodules for each half of the roots were unaffected by the nitrate applied to the other half. However, the nitrate induced significantly lower nitrogenase activity in the applied half. In the application for 30 days, nitrate induced a significantly higher nitrogen content in the applied half of the roots, and the inhibitory effect on nodulation and nodule development was observed not only in the applied half but also in the other half. Thus, the inhibitory effect of long-term nitrate application on the nodulation and nitrogenase activity of peanut may be systemic, but that of short-term nitrate application, in which external nitrate may regulate nitrogen fixation, may not be systemic.     

The inheritance of nitrate content in lettuce (Lactuca sativa L.)

Summary The inheritance of nitrate content in lettuce was analysed using 16 F₂ populations and three F₃ populations. Frequency distributions of nitrate content in F₂ and F₃ populations were unimodal and symmetrical, indicating a quantitative inheritance. Both significant positive and negative deviations of the F₂ mean from the mid-parent value were found, indicating dominance or epistasis. Deviations towards low nitrate content were more frequent than deviations in the other direction. Estimates of heritabilities for nitrate content in the F₂ populations ranged from 18% to 69% and were in most cases above 50%. Crosses between low nitrate cultivars did not have lower estimates of heritability in the F₂ than crosses between cultivars with larger differences in nitrate content. In one case a genotype x experiment interaction for nitrate content of parental cultivars was found.Three F₃ populations of crosses between cultivars with low nitrate content were analysed. Estimates of heritabilities for F₃ line means ranged from 78% to 91% and estimates of the genetic standard deviation of nitrate content in unselected advanced generations ranged from 0.24–0.33 g kg^–1. The estimates of heritabilities and of genetic variation in advanced generations offer good prospects of selection of low nitrate genotypes in lettuce. A comparison of efficiency of selection in the F₂ generation and F₃ line selection is made.     

加工番茄氮肥用量与氮营养状况诊断研究

通过设置N0(不施氮)、N1(150 kg/hm2)、N2(300 kg/hm2)和N3(450 kg/hm2)4个氮水平的田间小区试验,利用反射仪法对加工番茄新功能叶的叶柄进行硝酸盐测定,并测定地上部分生物量与经济产量,研究叶柄硝酸盐浓度与产量、叶全氮量、植株全氮量、地上部分干物质量等的相关性,建立加工番茄叶柄硝酸盐诊断追肥模型。结果表明,优化施氮处理(N2)经济产量为95 259 kg/hm2,较不施氮处理(N0)增产50 812 kg/hm2,增收14 988元/hm2。各处理加工番茄叶柄硝酸盐浓度随生育期进展呈一致的变化趋势,且叶柄硝酸盐含量在一定范围内随施氮量的增加而增大。加工番茄不同生育时期叶柄硝酸盐浓度与产量均呈显著相关性。经过校检,加工番茄以盛果前期为氮营养诊断时期较为合理,其临界值为4 182 mg/L。同时,初步建立了植株硝酸盐诊断追肥模型。     

太湖地区主要水稻土中硝态氮水平运移规律的研究

对太湖地区主要水稻土乌栅土中硝态氮水平运移规律的研究结果表明 :硝态氮的浓度随供试示踪剂源距离的增加而减小 ,其变化趋势呈对数曲线关系。硝态氮水平运移过程中 ,硝态氮浓度与含水量有密切的关系 ,硝态氮浓度随土壤含水量的增加而成比例增加 ,呈指数曲线关系。硝态氮的运移速率与运移距离有很好的相关性 ,并呈幂函数关系。从供试的示踪剂源开始到距离 2 0 cm时 ,硝态氮的运移速率主要由硝态氮的浓度梯度和水势梯度控制 ;而在 2 0 cm以后 ,则趋于平稳 ,这时主要由土壤的基质势起作用。     

用硝酸根电极快速测定蔬菜中的硝酸盐含量

详细介绍了硝酸根电极测定蔬菜硝酸盐氮的方法。从回收率试验、对比试验和精密度试验结果评价，该方法简便、快捷、准确，可用于蔬菜硝酸盐的快速测定。     

植物吸收转运硝态氮及其信号调控研究进展

硝态氮是植物吸收利用的主要氮源,其吸收利用是一个高度协调复杂的调控过程。植物为了在各种变化的环境中生存,进化出了适宜不同环境的硝态氮吸收利用机制。植物根系中存在不同类型的硝态氮受体,可以感受外界硝态氮浓度变化,并启用高亲和力或低亲和力硝态氮吸收系统,从而吸收硝态氮;硝态氮进入根系后,大部分被运输到地上部进行同化作用,合成大分子物质,以促进植物生长;如果地上部硝态氮含量过多,植物可把多余的硝态氮运送到液泡内储存,待需要时再从液泡转运至细胞质中利用。植物生长发育过程中,老叶和成熟叶片中的硝态氮可被转运到新生组织中,促进新生组织生长。硝态氮吸收利用过程中大量硝态氮吸收、转运、储存、同化和信号调控基因被有序激活并协调工作,促进植物高效吸收利用硝态氮。本文主要针对NRT1和NRT2硝态氮吸收转运相关基因及其功能,以及参与初级硝态氮反应的相关转录因子和小信号多肽在硝态氮信号传导和组织间的信号交流进行综述,以便深入理解植物吸收利用硝态氮的机理,为高效利用氮素的作物育种和栽培技术的创建提供新的思路。     

应用~（15）N示踪法研究芹菜的硝酸盐积累

本文用１５Ｎ示踪法研究了不同条件下芹菜对氮素的吸收利用与硝酸盐积累的变化。结果表明：芹菜的产量、总氮量、硝酸盐、ＮＯ３含量、硝酸还原酶活性（ＮＲＡ）均随施氨量的增加而增加;施用硝酸铵比施等氨量的硫铵、碳铵,使芹菜产量、总氨量、ＮＯ３－、ＮＲＡ明显增加;在等量氨肥的基础上,增施有机肥使芹菜ＮＯ３－含量增加,增施钾肥使芹菜ＮＯ３－含量下降。采收期芹菜体内累积的硝酸盐主要来自土壤。     

不同供N水平对花生硝酸盐累积与分布的影响

采用盆栽试验,研究了不同供氮水平对花生植株硝酸盐累积、分布及产量的影响。结果表明,花生荚果产量随施氮量的增加呈二次曲线变化趋势,当施用量为N.150.9.kg/hm2时产量最高;植株硝酸盐含量、累积量和累积速率基本随施氮量的增加而提高。同一氮素水平,不同器官的硝酸盐含量因生育期不同存在较大差异,幼苗和花针期茎中的含量最高,饱果成熟期地下器官的含量明显高于地上器官;全生育期叶片和茎中的硝酸盐含量随生育进程逐步降低,而子仁和果壳中含量逐步增加;收获时硝酸盐在茎中的分配比例随施氮量的增加而提高,在根中的分配比例下降。在一定的氮素水平内(N135.kg/hm2),硝酸盐在子仁中的分配比例与供氮水平一致,但过量施氮会导致在营养体中的比例上升,子仁中的比例下降,其它器官规律不明显。在本试验范围内,子仁及其它器官中的硝酸盐含量均未超出WHO和FAO制定的标准,未造成硝酸盐污染;但过量施氮能够显著提高花生荚果和耕层土壤硝酸盐含量。因此,综合考虑花生品质、单位肥料的增产量以及生态效应,花生适宜的施氮量为N.90.kg/hm2。