玉米幼胚离体培养和植株再生

系统研究了不同材料、不同培养基对玉米幼胚愈伤组织诱导及继代分化、植传再生的影响，结果发现，8个玉米自交系幼胚均能诱导出愈伤组织。但在继代过程中差异较大。将能继代的愈伤组织转入分化培养基进行生根培养。5010和综3自交系获得了再生植株。并且植株移栽可成活。     

Relationship between fatty acid profile and vitamin E content in maize hybrids (Zea mays L.)

The balance between the vitamin E (tocochromanols) and polyunsaturated fatty acid (PUFA) contents mainly determines the susceptibility to lipid peroxidation and the storage stability of corn oil. In 1997, field experiments were conducted at two different locations to evaluate a collection of 30 corn hybrids for fatty acid profiles and tocochromanol contents. Hybrids differed significantly (p < 0.01) for major fatty acids, as well as for tocochromanol contents and composition. The major fatty acids were palmitic, oleic, and linoleic acids, whose contents were in the ranges 9.2-12.1%, 19.5-30.5%, and 53.0-65.3%, respectively. The tocopherol contents ranged as follows: alpha-tocopherol, 67-276 mg (kg of oil)(-1); beta-tocopherol, 0-20 mg (kg of oil)(-1); gamma-tocopherol, 583-1048 mg (kg of oil)(-1); delta-tocopherol, 12-71 mg (kg of oil)(-1); total tocopherol, 767-1344 mg (kg of oil)(-1). gamma-Tocopherol was the predominant derivative among all tocopherols. The tocotrienol contents were in the ranges 46-89, 53-164, and 99-230 mg (kg of oil)(-1) for alpha-, gamma-, and total tocotrienol contents, respectively. The tocotrienol profile was not characterized by the predominance of any tocotrienol homologue. alpha-Tocopherol was positively correlated with PUFA (r = 0.41) and with the vitamin E equivalent (vit E equiv) (r = 0.84), and it was not correlated with gamma-tocopherol. gamma-Tocopherol was highly correlated with total tocopherol and tocochromanol contents (r = 0.93 and r = 0.90, respectively), indicating that the contribution of this vitamer to the total tocochromanol content is the most important among all tocochromanols. The high positive correlation found between the vit E/PUFA ratio and the vit E equiv, as well as the absence of correlation between this ratio and PUFA indicates that a higher vit E/PUFA ratio can be easier achieved be increasing the vitamin E content than by modifying fatty acid profile in corn oil.     

Hand planter for maize (Zea mays L.) in the developing world

Third world maize (Zea mays L.) production is characterized by having extremely low yields, attributed in part to the poor planting methods employed. Maize planting in most third world countries involves placing 2–3 seeds per hill, with hills being roughly 30 cm apart. The variability in seeds per hill and distance between hills result in heterogeneous plant stands that are directly responsible for lower yields. Oklahoma State University (OSU) has developed a durable hand planter with a reciprocating internal drum that delivers single maize seeds per strike and that can also be used for mid-season application of urea fertilizer. The hand planter is 1.4 m in length, 5.8 cm in diameter, and weighs 1.9 kg when empty. The seed hopper has the capacity to hold 1 kg of seed and the tip has a sharp pointed shovel which can deliver seed to a planting depth of 5 cm in no-till and tilled soils. The current prototype has been comprehensively tested and evaluated to deliver at least 80% single seeds (singulation), with 0% misses and work well across varying seed sizes (2652–4344 seeds/kg) and different operators. Using the OSU hand planter, third world maize producers with average yields of 2.0 Mg ha^?1 could increase yields by 20%.     

Brassinolide effects on maize (Zea mays L.) growth and yield under waterlogged conditions

Our aim was to assess if Brassinolide (BR) could ameliorate stress caused by waterlogging on maize. Two BR levels (with and without), two maize varieties [Ikom White (IKW) and Obatanpa-98 (Oba-98)] and three growth stages [control (WL_o), seedling stage (WL₁), and tasseling stage (WL₂)] were studied under waterlogging lasting 10 days. Maize growth and development were significantly (p?≤?.05) reduced by waterlogging stress under WL₁ than WL₂. Waterlogging stress at WL₁ adversely affected (p?≤?.05) the protein and relative water contents. The nitrogen (N) content among the plant partitions (leaves, stems, and grains) were reduced (p?≤?.05) at both silking and harvest. The beneficial effect of BR was more pronounced in Oba-98 with higher protein contents, dry matter yield, N-uptake and harvest index than IKW. Oba-98 was also better yielding than IKW. Thus, in a waterlogged soil, treatment of maize plants with BR at WL₁ could induce some tolerance.     

Cell wall composition in juvenile and adult leaves of maize (Zea mays L.)

Many leaf characteristics vary with position along the culm in maize (Zea mays L.) due to the existence of vegetative phase change and heteroblasty. The objective of this work was to determine if differences in cell wall composition exist among developmental phases and between Cg1, a developmental mutant, and wild-type maize. In one experiment, the middle third of fully elongated leaf blades from lower and upper regions of the shoot was harvested (midribs removed) and analyzed for several cell wall components. Averaged over five inbreds (De811, Ia5125, Mo17, P39, and Wh8584), lower leaf blades had higher levels of xylose and lower levels of total uronosyls, glucose, arabinose, and galactose (P < 0.05) than did upper leaf blades. With the exception of glucose, upper and lower leaves of Cg1 plants varied in the same manner as their near-isogenic siblings, except cell walls of Cg1 plants were more "juvenile" than cell walls of wild-type siblings at the same leaf stage. These data support the hypothesis that Cg1 delays but does not eliminate the transition from juvenile-vegetative to adult-vegetative phase. In a second experiment, juvenile (leaves 3 and 5), transition (leaf 7), and adult (leaves 9 and 11) leaves from inbreds B73 and De811 were harvested and analyzed as in the first experiment. As leaf number rose, total cell wall content of sample dry matter, total neutral sugars, glucose, xylose, and ester-linked monomers of p-coumaric acid and total ferulates including ferulate dimers increased linearly while total uronosyls acids, arabinose, and galactose declined linearly (P < 0.05). Glucose and xylose are major cell wall components released from cellulose and xylans after acid hydrolysis. Pectin, a minor component of grass cell walls, is composed of galacturonosyls, arabinose, and galactose. Secondary cell wall deposition increased between leaves 3 and 11 in a heteroblastic series, due to either increased cell wall content concomitant with decreased cell lumen size, changes in proportion of cell types (i.e., sclerenchyma), or a combination of these factors.     

Influence of rhizosphere bacteria on morphological characteristics of maize seedlings (Zea mays L.)

The effect of a rhizosphere microflora on some morphological and physiological plant characteristics was studied with maize seedlings grown for five days in a mineral nutrient solution. In the presence of the microorganisms the root dry weight is lower than that of axenically grown plants due to a smaller diameter of the primary root. In addition, the root content of some vitamins and sugars is affected. Pure cultures of rhizosphere bacteria were isolated and their influence on morphological characteristics of the maize plant was classified. Whereas one culture retards the overall plant development, the remaining nine cultures exert a significant influence only on specific morphological parameters. These results are discussed as an indication of the participation of phytohormones in interactions between roots and bacteria.     

Diversification of maize (Zea mays L.) through teosinte (Zea mays subsp. parviglumis Iltis & Doebley) allelic

Genetic Resources and Crop Evolution - Zea mays&nbsp;ssp.&nbsp;parviglumis&nbsp;is the progenitor of maize and assume to have tolerance against various biotic and abiotic stresses. It...     

Variation among maize (Zea mays L.) accessions of Bendel State,Nigeria

Summary Variability in maize zein protein band mobilities in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was characterized to classify 27 maize accessions (OTUs) collected from Bendel State, Nigeria. The classification of the OTUs was achieved using two numerical procedures: average linkage cluster analysis and principal component analysis (PCA). Five clusters were delineated by the cluster analysis whereas the PCA complemented the cluster analysis by separating the OTUs with yellow kernels into one group and OTUs with early maturity into another. OTUs from the same geographical contiguity commonly grouped together. However some regional overlappings of the OTUs occurred. Results of the PCA revealed that zein bands that stained less intensely more strongly separated the OTUs into various clusters than did those that stained more intensely.     

Influence of iron nutrition on sulphur uptake and metabolism in maize (Zea mays L.) roots

Abstract

Recent research has evidenced a relationship between Fe nutrition and S nutrition. Aim of the present work was to investigate the effect of Fe deficiency on the capacity of maize roots to take up and metabolize S. Maize (Zea mays L. cv. Cecilia) plants were grown for 10 d in nutrient solution (NS) with (+S) or without (?S) sulphate and Fe was added as Fe^III-EDTA at 80 μm. After removing the extraplasmatic Fe pool, half of the plants of each treatment (+S and ?S) were transferred to a new Fe-free NS. Roots were collected 4 and 24 h from the beginning of Fe deprivation. Fe deprivation slightly increased root thiols content in both nutritive conditions (+S and ?S). ATP sulphurylase activity was enhanced by sulphur deprivation, but greatly depressed when Fe and S were both omitted from the nutrient solution. O-Acetylserine sulphydrylase activity was also enhanced by S deprivation; this activity was increased by Fe starvation in +S plants, while it was unaffected by Fe nutrition in ?S plants. S deprivation greatly increased uptake rates of ³⁵SO₄ ^2? (1.9 ± 0.1 vs. 5.2 ± 0.2 μmol g^?1 root d.w. h^?1); furthermore, Fe deficiency increased ³⁵SO₄ ^2? uptake rates by 11 and 55% in +S and ?S plants, respectively. Data show that Fe-deficiency in maize results in a higher ability to take up sulphate, while limiting the first step of S assimilation in S deprived plants.     

Nitrogen fertilization does not affect micronutrient uptake in grain maize (Zea mays L.)

Abstract

Due to continuous single nitrogen fertilization, we hypothesized a built-up deficiency of micronutrients in crops that would limit plant growth and crop quality. In 2-year field experiments using urea-N fertilized grain maize (Zea mays L.), hybrid KWS 2376 at 0, 120 and 240 kg N ha^?1 crop uptake of Zn, Mn, Cu and Fe was studied at DC 32, DC 61 and in the grain harvested. Micronutrient contents at DC 32 stage – 1st node (aboveground phytomass) and DC 61 – flowering (ear leaf) were all at levels indicative of adequate micronutrient supply to the crop. At both sampling occasions the Fe:Zn and Fe:Mn ratios were adequate implying that Fe did not inhibit the uptake of Zn and Mn. The application of nitrogen increased the Fe content at the 1st sampling in both years; in the second year the same was also the case for the Zn content. Nitrogen nutrition increased the contents of Mn and Fe at the 2nd sampling only in year 2; in the other treatments no changes were observed in the micronutrient contents. Micronutrient correlations in the grain were discovered between Zn and Mn contents and between Fe and Mn contents. In the second year the highest N-rate significantly increased the Fe and Zn content of the grain compared with the lower rates of nitrogen fertilization. Grain yields were not affected by the rate of nitrogen and ranged between 13.65 and 14.34 t ha^?1 (1st year) and between 13.68 and 14.18 t ha^?1 (2nd year). Nitrogen fertilization did not reduce the content of micronutrients in the plant or grain of maize. It is evident that the continuous single use of N fertilization so far has not resulted in a micronutrient deficiency of the plants limiting the nutrient density of the grain or reducing its quality.     

Corn (Zea mays L.) root exudates and their impact on 14C-pyrene mineralization

Corn (Zea mays L.) root exudates were flushed from a hydrophobic system that allowed the aseptic separation of soluble exudates from the intact plant root. Plants were grown for 90 d, during which time root exudates flowed from the hydroponic setup directly onto columns containing soil previously contaminated with polycyclic aromatic hydrocarbons (PAHs). Mineralization of the PAH, pyrene, was then determined in soil removed from columns. In addition, exudated samples were directly taken from the hydroponic system for estimation of total organic carbon release and for use in microbial studies. In soil from columns that received root exudates from a planted (versus an unplanted) apparatus, there was a significant increase in ¹⁴C-pyrene mineralization. The extent of stimulation was comparable to that measured in rhizosphere soil isolated from plants growing in the same soil. Soil from columns that received solution from apparatuses that were not planted showed no stimulation of ¹⁴C-pyrene mineralization. Separate studies confirmed that some members of the soil microbial community were able to utilize these soluble plant compounds. This indicates that root exudates have the potential to increase the degradation of xenobiotics by the growth of soil microorganisms. Separating the chemical impact of the root exudates from any root surface phenomena is an important step in isolating a potential mechanism of phytoremediation. Many studies have speculated on the involvement of root exudates in rhizosphere degradation of organic contaminants, but very few studies go beyond adding simple carbon substrates in short pulses. This study employed a system that exposed the microbial community to real root exudates in the concentrations and over a time period that mimicked actual conditions.     

Denitrification with and without maize plants (Zea mays L.) under irrigated field conditions

The study was conducted under irrigated field conditions to examine the effect of maize plants on denitrification. Both planted and unplanted field plots received 150kgNha^–1 as urea. In a third treatment, which was also planted and received urea at 150kgNha^–1, the soil nitrate N content was brought up to equal to that in the unplanted plots by applying additional doses of N as calcium nitrate. Soil cores were collected 24 and 72h after irrigation and the denitrification rate was measured by the acetylene inhibition method. Nitrate-N content, aerobically mineralizable C, microbial biomass carrying capacity and denitrification potential were also studied on field-moist soil. Maize plants grown under field conditions always had the potential to increase denitrification in conditions of both high and low water-filled porosity. When nitrate-N content of the planted soil decreased due to plant uptake, denitrification was reduced in the planted soils. However, when nitrate-N uptake by plants was compensated through additional doses of nitrate fertilizer, denitrification was always higher in planted than unplanted soil. The stimulatory effect of plants on denitrification was observed at both high and low soil nitrate-N concentrations, though it was more pronounced at high nitrate-N levels. The effect of plants on denitrification and related parameters was confined to the root zone. Received: 15 April 1996     

运用多隔层根箱研究玉米幼苗根际微域中芘的降解

采用多隔层根箱,通过尼龙撩网插片的控制,实现根室土(S0)、离根室0～2mm(S1)、2～4mm(S2)、4～6mm(S3)及6mm(S4)各室层土壤的分离采集,分析离根系表面不同距离土壤芘的根际降解,并借助脂肪酸甲酯(fattyacidmethylester,FAME)分析土壤微生物群落结构的空间响应机制。结果表明:种植玉米处理的各室层内土壤可提取态芘含量存在显著的不同,其大小顺序为S4S3S0S2S1;各室层微生物群落结构存在显著的变化,其中微生物生物量和丛枝菌根真菌特征脂肪酸含量表现出与土壤可提取态芘含量变化相反的变化趋势。未种植玉米处理的各室层土壤可提取态芘含量和微生物群落结构没有差异。土壤可提取态芘含量与微生物生物量和丛枝菌根真菌的特征脂肪酸呈显著负相关(p0.01)。     

Hormonal interactions in the rhizosphere of maize (Zea mays L.) and their effects on plant development

The phytohormones indole acetic acid (IAA), abscisic acid (ABA), isopentenyladenosine (iPA), dihydrozeatin riboside (DHZR), and zeatinriboside (ZR) were determined quantitatively using monoclonal antibodies by an enzyme immunoassay in the following samples: a) culture filtrates of known bacterial species, growing naturally in close, loose or without contact with higher plants; b) culture filtrates of heterogeneous populations of microorganisms, isolated from the rhizoplane and rhizosphere of maize as well as from root-free soil; c) sterile and nonsterile maize root exudates; d) in the rhizosphere of field-grown maize plants and in soil fractions distant from the roots (bulk soil). ABA was not detected in the culture filtrates of bacteria and ZR was not found in bulk soil and rhizosphere soil of field-grown maize. All phytohormones were present in the other samples analyzed. Bacterial cultures with cell concentrations roughly equal to those in the rhizosphere of field-grown maize may produce under optimal laboratory conditions phytohormone concentrations comparable to those measured in the rhizosphere of field-grown maize. During the whole vegetation period there was a steep phytohormone gradient in the first centimeter of soil around a maize root in the field. Inoculation of maize seedlings growing in nutrient solution with rhizosphere bacteria resulted in a synergistic increase in phytohormone concentration in comparison to the sum of hormone production by sterile plant roots and by bacteria cultures. Using regression analysis, the relationship between phytohormone concentration changes in the rhizosphere and different morphological characteristics of the maize plant were shown to be highly significant.     

Response of maize (Zea mays L.) to potassium nano-silica application under drought stress

Abstract

To investigate the influence of potassium nano-silica (PNS) on maize plant under drought stress including non-stress (NS), moderate drought stress (MDS) and severe drought stress (SDS), a factorial experiment was conducted with completely randomized blocks with three replications. Drought stress decreased the concentrations in the shoot of phosphor (P), calcium (Ca), iron (Fe), zinc (Zn), manganese (Mn) and silica (Si) and nitrogen (N), P, Ca, Fe, Zn, copper (Cu), Mn and Si concentrations of seed. There was an increase in the concentration in the N seed and shoot potassium (K) concentration under drought stress. It was observed that applying PNS increased nutrient absorption. The highest concentration of N in the seed was obtained at 100?ppm PNS. The highest concentrations of seed K and N, Cu, Mn and Si in the shoot were found when 200?ppm of PNS was applied. Applying PNS had no significant effect on the concentrations of P, Ca, sodium (Na) and Cu in the seed, and of Ca and Na in the shoot. These findings demonstrate that the application of PNS can limit the negative effects of drought stress and improve plant’s resistance against drought stress.     

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.     

Arsenic accumulation and distribution in the tissues of inbred lines in maize (Zea mays L.)

We investigated arsenic (As) accumulation and distribution in four different tissues of maize, leaves, stems, bracts, and kernels. For these analyses, we used 122 elite inbred lines, which were grown in an As-contaminated area in China. The agricultural soil at the study site is highly As-contaminated (11.02?±?0.95?mg?As?kg?soil^?1) because of excessive use of As-rich surface water for irrigation. The As concentration in the leaves was significantly positively correlated with that in stems and kernels, and the As concentration in the stems was significantly positively correlated with that in the kernels. In the 122 inbred lines, the highest average As concentration was in the leaves, followed by the stems, the bracts, and then the kernels. The range of As concentrations in leaves, stems, bracts, and kernels of the 122 inbred lines was 0.13–1.48, 0.017–0.145, 0.013–0.131, and 0.0001–0.0408?mg?As?kg^?1, respectively. The inbred lines with low As concentrations in the kernels perhaps could be used as a parent to select an elite hybrid with low As concentration for decreasing the As damage for people and animal.     

Improving iron bioavailability and nutritional value of maize (Zea mays L.) in sulfur-treated calcareous soil

Soil factors such as pH, calcium, carbonate, and bicarbonate precipitation products in calcareous soils reduce iron (Fe) availability to crops and limit grain Fe concentrations. In the present greenhouse study, we evaluated the potential of Fe fertilizer amendments combined with organic amendments, like biochar (BC) and poultry manure, in sulfur (S)-treated low pH calcareous soils (pH_S1) to assess Fe biofortification of maize. Elemental sulfur (S) was used both for lowering soil pH and Fe solubilization. Soil pH was successfully lowered down from 7.8 to 6.5 by S application at the rate of 2.5 g kg^?1 soil. Pot experiment results revealed that Fe fertilizer combined with BC and S (pH_S1) significantly increased root and shoot dry weight, grain weight, photosynthetic rate, transpiration rate, and stomatal conductance by 69%, 86%, 28%, 74%, 57%, and 33%, respectively, relative to the control. Similarly, combined application of Fe + BC in S-amended (pH_S1) soil increased starch (34%), protein (64%), and fat (1 fold) while antinutrient phytate and polyphenols were decreased up to 29% and 40%, respectively, over control. Regarding the maize nutrients profiles, application of Fe with BC gave the maximum increase of Fe and ferritin was increased 1.7 fold at pH_S1. The results of this study showed that Fe fertilization with BC at pH_S1 soil is beneficial for crop growth and Fe bioavailability.     

Effect of land use types on decomposition of 14C-labelled maize residue (Zea mays L.)

The effect of three land use types on decomposition of ¹⁴C-labelled maize (Zea mays L.) residues and soil organic matter were investigated under laboratory conditions. Samples of three Dystric Cambisols under plow tillage (PT), reduced tillage (RT) and grassland (GL) collected from the upper 5 cm of the soil profile were incubated for 159 days at 20 °C with or without ¹⁴C-labelled maize residue. After 7 days cumulative CO₂ production was highest in GL and lowest in PT, reflecting differences in soil organic C (SOC) concentration among the three land use types and indicating that mineralized C is a sensitive indicator of the effects of land use regime on SOC. ¹⁴CO₂ efflux from maize residue decomposition was higher in GL than in PT, possibly due to higher SOC and microbial biomass C (MBC) in GL than in PT. ¹⁴CO₂ efflux dynamics from RT soil were different from those of PT and GL. RT had the lowest ¹⁴CO₂ efflux from days 2 to 14 and the highest from days 28 to 159. The lowest MBC in RT explained the delayed decomposition of residues at the beginning. A double exponential model gave a good fit to the mineralization of SOC and residue-¹⁴C (R² > 0.99) and allowed estimation of decomposition rates as dependent on land use. Land use affected the decomposition of labile fractions of SOC and of maize residue, but had no effect on the decomposition of recalcitrant fractions. We conclude that land use affected the decomposition dynamics within the first 1.5 months mainly because of differences in soil microbial biomass but had low effect on cumulative decomposition of maize residues within 5 months.