Changes in Anthocyanin Content as Indicator of Maize Sensitivity to Selenium

The aim of this experiment was to examine the effect of exogenous selenium (Se) on anthocyanin and chlorophyll accumulation, Se content, as well as the growth of maize (Zea mays var. ‘saccharata Kcke’) cv. ‘Zlota Karlowa’ seedlings. Plants were grown hydroponically in Hoagland's nutrient solution at different pH values: 4.5, 6.2, and 7.5. Selenium was added to the solution as either selenate (Na₂SeO₄) or selenomethionine (C₅H₁₁NO₂Se) to a final concentration of: 0 (control), 5, 25, 50, and 100 μ M Se. Generally, the presence of Se in the medium caused an increase in the anthocyanin content and a simultaneous decrease of the total chlorophyll concentration depending on the Se form and dosage. Higher concentrations of anthocyanin were detected in the presence of selenomethionine than selenate, notably at pH 4.5. The effect of individual Se forms on maize seedlings, expressed on the basis of the fresh weight, indicate that selenomethionine was more phytotoxic than selenate. Selenium content both in roots and shoots increased linearly with increasing Se concentration in solution culture. However, a much higher Se level was found in the maize organs when plants were supplied with selenomethionine than selenate. Experimental evidence shows that the changes in anthocyanin content can be used as a test parameter reflecting the degree of Se toxicity in maize plants, and may be potential useful for bioindication of Se phytotoxicity in other higher plants.     

Kinetics of 15N-labelled nitrate uptake by maize (Zea mays L.) root segments

Abstract

Isotherms and kinetic constants of nitrate uptake by excised root segments from the apical root zone of 6-d-old maize seedlings pretreated with nitrate were investigated using ¹⁵N-labelled nitrate. The isotherms were resolved into two systems namely a multiphasic saturable system at substrate concentrations lower than 2 mol m^?-3 and a linear system at higher concentrations. The detailed analysis of the multiphasic saturable system suggested the existence of at least three phases, which followed the Michaelis-Menten kinetics. The I _max and K _m of each phase increase from the lower phase to the upper phase. The distance from the root tip and the presence of stele affected considerably the linear system but only slightly the saturable system.     

N、P、K肥对玉米幼苗吸收和积累重金属的影响

采用室内盆栽试验,研究复合污染土壤中施加氮肥（NH4Cl）、磷肥（Na2HPO4）和钾肥（KCl）对高生物量经济作物玉米（Zeamays L.）幼苗生长以及吸收和积累重金属的影响。结果表明,不同施肥方式和浓度处理对玉米生物量变化以及吸收重金属有不同影响,NH4Cl能显著提高玉米地上部生物量、土壤Pb、Cd有效态含量,增加玉米对重金属Pb、Cd、As的提取量,最大分别可提高1.7、2.0倍和1.2倍。不同施肥方式和处理浓度均显著影响土壤有效态Pb含量,Na2HPO4在中浓度处理时显著降低土壤Pb的有效性,高浓度时则显著增加土壤有效态As含量,使玉米地上部对As的积累量有明显提高。在不同的浓度水平下,钾肥处理使玉米提取Pb含量显著高于氮肥和磷肥,其中低浓度KCl处理使玉米提取Pb量比对照增加2.4倍。对Pb-Cd-As复合污染农田土壤来说,施用氮肥（NH4Cl）处理对强化玉米的修复效果最好。     

不同耐密性玉米品种的根系生长及其对种植密度的响应

根系形态和分布对土壤中养分和水分的吸收有重要影响。增加耐密性是现代玉米（Zea may L.）育种的主要方向,而耐密性与根系的关系尚了解不多。本文以70年代主推的2个不耐密型品种（中单2号与丹玉13）和2个当代耐密型现代品种（先玉335和郑单958）为材料,将田间试验和室内水培试验相结合,在3个密度水平下,研究了不同耐密性玉米品种的根系差异及其对种植密度的响应。结果表明,目前推广的耐密型品种的根系要小于不耐密的老品种。不同耐密性品种之间的差异主要表现在040 cm。随着密度的增加,根显著变小、变细。密度主要降低020 cm土层中的根系生长,对深层根系影响较小。先玉335和中单2的根系长度对密度的反应较弱,郑单958和丹玉13较强。这说明先玉335主要依靠其小根系适应高密度,而郑单958既依靠较小的根系,同时依靠较高的根系反应性适应高密度。     

玉米根系发育突变体及相关基因研究进展

根系形态以及生理特征与作物养分水分高效利用密切相关。利用根系发育突变体是研究根系结构与功能的主要手段之一。近10多年来,一些玉米根系发育的突变体被鉴定出来,其中包括影响节根发育的rtcs突变体,影响侧根发育的lrt1、slr1、slr2和rum1突变体,还有影响根毛发育的rth1、rth2和rth3突变体,其中部分突变体所对应的基因已经克隆。这些进展有利于人们更深入地认识玉米根系生物学特征在养分水分高效中的作用。     

Physiological Effects of Salicylic Acid and Thiourea on Growth and Productivity of Maize Plants in Sandy Soil

This study aimed to investigate the response of vegetative growth, yield, and some metabolic constituents of maize grains cv. Single Cross 124 to foliar applications of salicylic acid (SA; 100, 200, and 400 mg L^?1) and thiourea (TU; 500, 1000, and 1500 mgL^?1), two bioregulators, either alone or in combination. The foliar application of SA and TU alone significantly increased stem diameter, number of leaves?/?plant, leaf area, total dry weight?/?plant, leaf area index, net assimilation rate, specific leaf weight, and yield (i.e., ear length, ear diameter, number of grains?/?row, number of rows?/?ear, 100-grain weight, grain yield?/?plant, grain yield?/?fed (1 feddan = 4200 m²), harvest index, and shelling percentage) by increasing SA or TU concentrations up to 200 and 1500 mg L^?1, respectively. Salicylic acid and TU, when applied alone, significantly improved the nutritional value and quality of maize grains by increasing crude protein, total soluble sugars, total free amino acids, and total soluble phenols.     

地下部分隔对蚕豆/玉米间作氮素吸收和土壤硝态氮残留影响

利用田间试验,探讨了地下部分隔对蚕豆/玉米间作氮素吸收和土壤硝态氮残留的影响,结果表明:蚕豆/玉米间作,蚕豆不分隔条件下籽粒和秸秆吸氮量比分隔分别增加20 10%,34 43%;玉米不分隔条件下籽粒吸氮量与分隔近似,但秸秆吸氮量比分隔减少13 04%;蚕豆和玉米不分隔条件下土壤硝态氮累积量都高于分隔。蚕豆/空带间作,蚕豆不分隔籽粒吸氮量高于分隔,但土壤硝态氮累积量没有差异。空带/玉米间作,地下部分隔与否,作物吸氮量和土壤硝态氮累积量都没有差异。     

Characterization of Zinc Oxide Nano Particles and Their Effect on Growth of Maize (Zea mays L.) Plant

In the current literature, the impact of nano-particles (NPs) on growth of higher plants has scantly been reported. An investigation was carried out to study the effect of zinc oxide nano-particles (<100 nm) on growth of maize (Zea mays L.) plant, as one of the major agricultural crops, in a solution culture system. Various concentrations of zinc (Zn) were applied through nano-zinc oxide (ZnO) particles (<100 nm) in suspension form and in ionic form through zinc sulfate (ZnSO₄) salt in Hoagland solution culture. Experimental results showed that nano zinc oxide particles could enhance and maintain the growth of maize plant as well as conventional Zn fertilizer (as ZnSO₄). The plant parameters like plant height, root length, root volume, and dry matter weight were all improved due to application of zinc oxide nano-particle. These findings indicate that plant roots might have the unique mechanism of assimilating nano-Zn and using for its growth and development. Different enzymatic activities were also studied and experimental results revealed that nano-ZnO particles (<100 nm) also governed the enzymatic activity of maize plant. A separate laboratory experiment was also carried out to characterize the zinc oxide nano particle for its size, zeta potential, etc.     

Sources,Rates and Time of Nitrogen Application on Maize Crops under No-Tillage System

Quantitatively, nitrogen (N) is the foremost nutrient for maize crops (Zea mays L.), but the N source to increase the grain productivity still needs more investigation. Thus, the aim of this experiment was to study sources, rates and time of N application on the crop yield and agronomic characteristics of the maize under no-tillage system. The experiment was carried out during two growing seasons on an Oxisol under the factorial 5 × 3 × 3 scheme with five N rates (0, 50, 100, 150, and 200 kg ha^?1) and three sources (ammonium-sulfate-nitrate as inhibitor of the nitrification (ASN+I), ammonium sulfate (AS) and urea); we applied them two times with four replicates: first time at the sowing or later under side dressing when the plants had the six leaves stage. In the first year, the sources of N had no influence on the number of grain line /ear (NGLE), grain number/line (GNL), total number of grain/ear (TNFE), biomass of 100 grain, plant height (PH), height of the first ear insertion (AFEI) and stalk diameter, in contrast with the foliar N content and the crop yield. Early fertilization with N at the sowing time can afford applications as well as the total side dressing. The increase of the rates had positive influence on the N foliar content, plant height and 100 grains biomass. The highest productivities were found with rates above the threshold of 150 kg ha^?1, no matter the sources and the fertilization time.     

Effects of Soil Fertility Management on Growth,Yield, and Water-Use Efficiency of Maize (Zea mays L.) and Selected Soil Properties

Maize was grown for two cropping years to investigate the supplementary effect of inorganic fertilizer with cow dung on growth, yield, water-use efficiency, and soil properties. Five treatments were imposed: unfertilized control and four different fertilization packages comprising two different levels of inorganic fertilization with cow dung as supplements, sole inorganic fertilizer, and sole cow dung. Results analyzed after the two cropping years showed significant differences in growth and yield. A reduction in yield was observed for the unfertilized plots, whereas yields in the plots of supplemented inorganic fertilizer with cow dung increased and were significantly at par with the sole inorganic fertilizer plot. Water-use efficiency was improved for the fertilized plots. Significant improvement was observed in the water-stable aggregates with plots that received cow dung as organic manure either in part with inorganic fertilizer or as sole cow dung.     

Effects of Phosphorus Fertilizer Source and Plant Density on Growth and Yield of Maize in Northwestern Pakistan

ABSTRACT

Phosphorus (P) fertilizer source and plant density are considered some of the most important factors affecting crop growth and yield. A field experiment was conducted to determine the impact of P source [zero-P control, DAP (diammonium phosphate), SSP (single super phosphate), and NP (nitrphos)] and plant density (D₁ = 40,000, D₂ = 60,000, D₃ = 80,000, and D₄ = 100,000 plants ha^?1) on growth and yield of maize (Zea mays L cv. Azam) on a P-deficient soil (6.6 mg P kg^?1) at New Developmental Agricultural Research Farm, North-West Frontier Province (NWFP) Agricultural University, Peshawar, Pakistan, during summer 2006 in wheat-maize cropping system. Physiological maturity was delayed, plant height was increased and leaf area was decreased significantly when maize was planted at highest (D₄) than at lowest plant density (D₁). Application of SSP resulted in earlier physiological maturity of maize than other P fertilizers. Grain and stover yield, harvest index, shelling percentage, thousand grain weight and grains ear^?1 were maximized at D₃ (80,000 plants ha^?1) and with application of P fertilizer. Highest benefit in growth and grain yield was obtained with application of DAP to maize planted at D₃. Application of DAP at D₃ gave 15, 29, and 19% higher grain yield than its application at D₁, D₂, and D₄, respectively. In conclusion, the findings suggest that growing maize at 80,000 plants ha^?1 applied with DAP can maximize productivity of maize in the wheat-maize cropping system on P-deficient soils.     

一氧化氮改善铁胁迫玉米光合组织结构及其活性

一氧化氮(NO)影响植物生长发育过程及其机制是近年来的研究热点,在植物生长发育的多个层面起着重要的作用。以硝普钠(SNP)为一氧化氮发生剂,液体培养20.d龄的玉米幼苗叶片为实验材料进行研究,结果表明,NO可完全逆转玉米幼苗由缺铁引起的脉间失绿现象,极显著地提高叶片叶绿素含量。电镜观察结果证实,NO促进了玉米叶片叶肉细胞和维管束鞘细胞中叶绿体的发育,叶绿体数量增多且体积增大,基质片层和基粒数量明显增多且结构完好。同时,NO促进了缺铁玉米类囊体膜色素蛋白复合体的装配并显著提高了光合链的电子传递速率,使叶片光合活性得到极显著增加。     

Corn (Zea mays L.) Grain and Stover Yield as Affected by Soil Residual Mineral Nitrogen

Evaluation of nitrogen (N) dynamic in soil using regression equations is important for proper determination of N fertilization. A 3-year field experiment was conducted to (1) develop the best-fitted regression model relating corn grain and stover yield to soil residual ammonium (NH₄)-N and nitrate (NO₃)-N for corn yield prediction and (2) evaluate how such a model can be beneficial to the health of ecosystem by predicting the appropriate rates of N fertilization for corn production. Soil NH₄-N and NO₃-N were determined at corn harvest at the depths of 0–30 and 30–60 cm. Nitrogen fertilizer rates and soil mineral N accounted for a maximum of 93% variation in corn grain yield. Soil mineral N enhanced corn yield more than N fertilizer. Totals of 63.1 and 14.1 kg/ha of soil residual NO₃-N and NH₄-N were found in the 0- to 60-cm depth, indicating the importance of performing soil N tests.     

农田黑土中不同浓度乙草胺对玉米苗期生长的影响

通过黑土盆栽试验研究了施用化肥条件下不同浓度乙草胺对玉米苗期生长的影响。结果表明,虽然在整个取样期间,植株体内无乙草胺残留检出,但是乙草胺施用对玉米苗期的形态和生理指标均具有一定影响。植株中超氧化物歧化酶活性、地下部分过氧化物酶活性和株高、根长等形态指标在玉米生长前期发生明显变化,其变化趋势受到乙草胺施用量的显著影响。在施有等量化肥的条件下,低浓度和高浓度乙草胺的施用抑制了玉米的生长,但中等浓度乙草胺对苗期玉米的生长表现出一定的促进作用。随着种植时间的延长,乙草胺活性降低,植物体的各项抗性指标和生理指标趋于一致。     

Effect of population size and yield level in selection of diagnosis and recommendation integrated system (DRIS) norms

Abstract

A data bank comprising over 8000 observations of yield and tissue composition was assembled from a wide range of locations and conditions. DRIS norms were developed from parts of the data bank representing different sources and chronology in its development. The effects of population size and yield level used to discriminate between high and low yielding subpopulations on the DRIS norms are studied. The results indicate that the best banks are those which are large, random and have a substantial number of high yield observations.     

Nitrogen use efficiency and nutrient partitioning in maize as affected by blends of controlled-release and conventional urea

ABSTRACT

Blends of controlled-release urea (CRU) and conventional urea can be an alternative to conventional fertilization to improve nitrogen use efficiency (NUE) and reduce costs when applied as a single application to agricultural crops. Different indexes of NUE, grain yield, nutrient uptake and partitioning in maize (Zea mays L.) were investigated in field experiments. The treatments consisted of a single rate of 180 kg N ha^?1 with different proportions of polymer-sulfur coated urea (PSCU) and conventional urea (U) applied incorporated at sowing (0.05 m below and 0.1 m to the side of the seed row) at two tropical sites (Site 1, Typic Haplustox; Site 2, Rhodic Haplustox) in Brazil. A control treatment (without urea-N) and a treatment with conventional urea management (UCM: 20% of urea-N applied as basal fertilizer and 80% of N applied as top dressing) were also included. This study demonstrates that blends of PSCU and U are efficient in supplying N throughout the maize cycle at a Typic Haplustox site when applied in a single application incorporated at sowing, resulting in high yields and adequate macronutrient uptake. PSCU improved NUE index compared to U and UCM. There was not response for N fertilization in the Rhodic Haplustox site.     

Effects of Nitrogen Application on Chlorophyll Content,Water Relations,and Yield of Maize Hybrids under Saline Conditions

An experiment was conducted to assess whether accumulation of photosynthetic pigments, proline, and maintenance of water relation attributes relate to the yield of maize hybrids differing in salt tolerance. Two maize hybrids, Pioneer32B33 and Dekalb979, were grown at three salinity levels under four nitrogen treatments. The experiment was laid out in a three-factor randomized complete block design and there were three replications of each treatment. Salt stress significantly decreased leaf chlorophyll a and a/b contents, whereas chlorophyll b and total chlorophyll were slightly increased. Under salinity stress, relative water content decreased, and water potential and osmotic potential become more negative. As a result, turgor potential also decreased. Nitrogen application improved all the chlorophyll pigments, water-related attributes, and yield components. However, chlorophyll a/b ratio was decreased. Overall, because of the differential response of maize hybrids to salt stress in terms of their performance in photosynthetic pigments, water relations, and yield, it can be concluded that hybrid Pioneer32B33 might perform better, if grown under salinity regime and sufficient nitrogen was applied in the growth medium.     

Effect of Nitrogen Nutrition on Solute Accumulation and Ion Contents of Maize under Sodium Chloride Stress

Salinity is a major abiotic stress that limits the productivity of crops, particularly cereal crops, while decreasing nutrient availability, especially of nitrogen. An experiment was conducted to study the effects of salt stress [i.e., S₀, S₁, and S₂ (control, 1.09; 5; and 10 dS m^?1)] and four different nitrogen (N) levels [i.e., N₀, N₁, N₂, and N₃ (control, 175, 225, and 275 kg N ha^?1)] on two maize hybrids, Pioneer 32B33 (salt tolerant) and Dekalb 979 (salt sensitive). The experiment was conducted in a wire house. The experiment was laid out with three factors in a completely randomized design. The plant tissue was analyzed for solute and ion contents. With the increase in salt stress and N rate, solute (i.e., glycinebetaine), protein, total soluble sugar, and total free amino acids accumulated in both hybrids. Nitrate (NO₃) and nitrite (NO₂) reductase activity decreased sharply at 10 dS m^?1 compared to lower levels of salinity but it increased significantly with the addition of N. The uptake of potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), N, and phosphorus (P) reduced significantly in shoots with increased salinity while the sodium (Na⁺) and chloride (Cl) contents were increased. It is concluded from the present study that at greater salinity level, hybrid Pioneer32B33 maintained statistically greater solute and ion contents excluding Na⁺ and Cl ions and significantly decreased enzyme activity. However, these parameters were increased by N rate.     

Effect of pH on soil magnesium and its absorption by corn

Abstract

Lime induced depression of exchangeable Mg had been observed previously and it was postulated that yield decreases, which frequently occur at high pH levels may in some instances be due to Mg deficiency. This study was conducted to evaluate the influence of pH on exchangeable Mg in a wide range of acid soils and to determine the effects on recovery of Mg by corn (Zea mays L.) in the greenhouse. Treatments consisted of five pH levels, three P levels, and three Mg levels. Soil Mg was extracted with two neutral salt solutions and double acid. Salt extractable Mg decreased markedly at near neutral pH values, but double acid extractable Mg remained essentially unchanged. In several of the soils where yields were depressed at the highest pH levels, plant Mg content was also significantly lower. However, yield depressions were not ameliorated by Mg applications and could not be ascribed to induced Mg deficiency. Decreased plant uptake of Mg at both low and high pH levels was considered to have resulted from competitive effects between Mg and Al. The evidence suggested that salt extractable Mg did not accurately reflect plant availability.

Because soil reaction has profound effects on the availability of aluminum and many elements essential to plants, liming should be practiced primarily to optimize the utilization of the nutrient resources of soil. While pH values near neutrality are regarded as optimal in many areas of the world, particularly where legumes have traditionally been part of the rotational system, yield depressions have sometimes been reported at such pH levels on highly weathered acid soils of tropical and subtropical origin.     

Impact of Fertilization and Irrigation on the Correlation between the Soil Plant Analysis Development Value and Yield of Maize

The degree of nitrogen (N) supply in maize under nonirrigated and irrigated conditions was measured using a Soil Plant Analysis Development (SPAD) 502 portable chlorophyll meter for 4 years. The lowest readings were obtained from a plot that has not been fertilized for 23 years. The highest SPAD value in the nonirrigated treatments was obtained in 2004, whereas the lowest was measured in the drought year of 2007. In the irrigated treatments, there was a closer correlation between fertilization and SPAD values during the examined 4 years. As the result of fertilization, the average increase of SPAD values in the irrigated plots was greater than in the nonirrigated plots. The result of irrigation on SPAD values was significant every year (P < 0.001), with the largest increase in the drought year of 2003. In the nonirrigated treatments, fertilization and grain yield had a weak correlation, whereas in the irrigated treatments the correlation between the two variables was strong.