Colonization and growth promotion characteristics of Enterobacter sp. and Herbaspirillum sp. on Brassica oleracea

We investigated the effects of inoculating a dicot plant, Brassica oleracea , with nitrogen-fixing endophytic bacteria isolated from monocots. The bacteria used were Enterobacter sp. strain 35 isolated from sugarcane and Herbaspirillum sp. strain B501 isolated from wild rice. Under glasshouse conditions, B. oleracea inoculated with strain 35 had a significantly greater fresh weight than uninoculated plants, and the fresh weight of plants inoculated with strain B501 tended to be higher than that of uninoculated plants. We conducted a laboratory-scale experiment to confirm the above results and to investigate the colonization and nitrogen-fixing abilities of these bacteria. Plants inoculated with Enterobacter sp. strain 35-1, a green fluorescent protein (GFP)-labeled strain derived from strain 35, had larger bacterial populations and greater acetylene reduction activity than those inoculated with Herbaspirillum sp. strain B501 gfp 1. Strain 35-1 colonized the intercellular spaces and the junctions of the lateral roots with the parent root. The results indicated that isolates from monocots can successfully colonize B. oleracea (a dicot) and promote plant growth.     

春玉米品种和种植密度对植株性状和耗水特性的影响

品种和种植密度是辽西地区春玉米节水高产栽培的参考依据。以稀植型品种丹玉12(DY12)和密植型品种中地77(ZD77)为试验材料,各设4个种植密度处理,研究了种植密度对玉米植株性状、耗水量、产量性状、水分利用效率(WUE)的影响,同时比较两类型品种之间的差异。结果表明:随着种植密度增加,两品种茎粗、单株叶面积均逐渐降低,株高、群体叶面积指数(Leafarea index,LAI)逐渐增加,DY12茎粗和ZD77株高差异分别达到显著水平(P<0.05);同一种植密度条件下,DY12的茎粗、株高均大于ZD77,而ZD77的LAI大于DY12表现出较强的耐密性。玉米全生育期耗水量随种植密度的增加而增加,同一种植密度条件下,ZD77小于DY12。产量随着种植密度的增加先增加后减少。除穗粗、穗行数及百粒质量外,种植密度对DY12其余产量性状的影响达到显著水平(P<0.05);而种植密度对ZD77各产量性状的影响均不显著。在WUE方面,DY12随种植密度的增加先增大后减小,当种植密度为45000株/hm2时,WUE达到最大值(2.48kg/m3);ZD77则随种植密度的增加而减少。该地区生产上应选择密植型春玉米品种进行合理密植,可以达到明显的节水增产效果。     

土壤因子对链霉菌S506定殖和促生功能的影响

链霉菌S506是从植物根际分离获得的具有促生、防病和降解根系毒素功能的根际微生物,为了解土壤环境条件对其在根际定殖和功能表达的影响,以链霉菌S506为试材,研究了土壤质地、环境温度和土壤湿度对S506在番茄根际土壤定殖及番茄植株生长的影响.结果表明,适宜链霉菌S506在番茄根际定殖和促生作用发挥的土壤质地为壤土,其次为砂土和黏土;试验所设温度梯度中,利于S506在根际定殖的环境温度为30℃,其次为22.5℃和15℃,而利于目的菌株促生功能表达的环境温度则依次为22.5℃、30℃和15℃;适宜于目的菌株在根际定殖和促生功能发挥的土壤相对湿度为20%、25%,其次为15%和30%.     

Halotolerant rhizobacteria: beneficial plant metabolites and growth enhancement of Triticum aestivum L. in salt-amended soils

Salt-tolerant strains of Enterobacter asburiae, Bacillus thuringiensis, Moraxella pluranimalium and Pseudomonas stutzeri were evaluated for their ability to alleviate salt stress of wheat (Triticum aestivum L.) seedlings. 1-Aminocyclopropane-1-carboxylate deaminase activity of P. stutzeri S-80 and B. thuringiensis S-26 was 190 and 183 nmol h^?1, respectively. Maximum levels of auxin were recorded with P. stutzeri S-80 (107 µg ml^?1) and E. asburiae S-24 (143 µg ml^?1) under normal and salt-stressed conditions (0.25M NaCl), respectively, with 500 µg ml^?1 L-tryptophan. Auxin response mediated by rhizobacteria was also demonstrated by microscopically assaying the transgenic auxin-responsive reporter DR5::GUS expression tomato (Solanum lycopersicum L. cv. MicroTom). In pot trials, seedlings fresh and dry biomass witnessed highly significant improvements of 1- and 2.2-folds, respectively, with M. pluranimalium S-29 (at 100 mM NaCl) and E. asburiae S-24 (150 mM NaCl), over control. At final harvest, maximum increase in number of tillers (up to 94%) and seed weight (up to 40%) was recorded with E. asburiae S-24 and M. pluranimalium S-29 at 200 mM salt stress. In conclusion, newly isolated strains of M. pluranimalium S-29, E. asburiae S-24 and P. stutzeri S-80 enhanced the growth of T. aestivum by mitigating the salt stress of plants.     

Varietal traits limiting the grain yield of tropical maize II. The growth and yield of tall and short varieties

Four isogenic varieties with different heights, derived from the Tuxpeño population, were grown in the tropics to evaluate their potential productivity. Short varieties were developed by two means: incorporation of the brachytic-2 gene and current selections of shorter plants.

The tallest, original Tuxpeño produced the highest yield, next was the short-plant selection, while the brachytic varieties yielded least. Yield differences between the original and the short-plant selections were derived from the kernel size and the differences between those and the brachytic varieties, from the number of kernels.

Incorporation of the brachytic gene is unlikely to improve the productivity of varieties because it results in low efficiency of leaves in dry matter production during ripening, caused by the limited sink size and the compact distribution of wide leaves.     

Moderate soil compaction: Implications on growth and architecture in seedlings of 17 woody plant species

Generally, soil compaction is a stress factor affecting negatively the plant growth, but its effects vary between species and with the soil compaction range. The objective of this study is to know the different growth responses of 17 woody species subjected to moderate soil compaction, because most of the studies about this subject compare the effects in treatments with a wide and discrete compaction range. We explore the effects of moderate soil compaction on a continuous scale (0.1–1.0 MPa) on seedling growth. Seedlings of 17 woody species (deciduous and evergreens) mainly from Mediterranean ecosystems were grown in near optimal conditions (light, temperature and water) in a greenhouse with a sandy substrate. In general, there was a great variability of the responses depending on the species and the studied variable. About 53% of the species showed a higher total biomass with a moderate increase in soil compaction possibly being due to a greater root–soil contact. In the same way, 41% of species increase the relative growth rate and 35% the total area. Nevertheless, in spite of these positive effects on growth, for some species (23%) there was a decrease in the root proportion with soil resistance, as result of soil strength. These effects of moderate soil compaction could sum up in two general responses of woody plants: growth increment and architecture distortion. This might be relevant as a lower root investment may be a disadvantage under drought conditions. Finally, a simple conceptual model is proposed to understand the general effects of soil compaction on growth and biomass allocation.     

三种土壤上六种丛枝菌根真菌生长特征和接种效应

以分离于华北、华中和华南3个生态区及法国引进的丛枝菌根真菌为试验菌株,采用三室根箱培养的方法,研究了它们在华北、华中和华南3种典型土壤褐土、棕壤和红壤上的菌根形成、接种效应、磷吸收贡献和根外菌物量情况。结果表明,6种菌株在上述指标上存在显著的种间或生态型差异,土壤与菌株间存在显著的交互作用。6种菌株在3种土壤上都能与玉米形成菌根,在褐土和棕壤上大多数菌株在分离地所在地区土壤类型上的菌根侵染率较高,说明其对该土壤条件的适应性较强;在红壤强酸性土壤条件抑制了菌根真菌的侵染。菌株BEG168、BEG167、BEG151、BEG221和BEG141在褐土上,BEG151和BEG221在棕壤上,BEG168和BEG150在红壤上显著提高了玉米的生物量。在褐土和棕壤上,除BEG150外,BEG168、BEG167、BEG151、BEG221和BEG141能显著促进宿主吸磷;而在红壤上,BEG168和BEG141显著促进了宿主吸磷。若以真菌的根外菌物量作为衡量AM真菌菌株土壤生态适应性的指标,BEG141和BEG167是生态适应性强的菌株,为广幅生态型菌株;菌株BEG168和BEG151次之,前者在棕壤上适应性高,后者在红壤上适应性高。BEG150和BEG221生态适应性较窄,仅适应红壤或褐土,为窄幅生态型菌株。Glomus.etunicatum的两个生态型BEG168和BEG221在土壤生态适应性上差异很大,前者在两种土壤上收集到菌物量,而后者只在褐土上收集到菌物量。土壤条件可以决定丛枝菌根真菌的生长状况和功能。     

Influence of plant growth regulators and humic acid on the phytoremediation of lead by maize in a Pb-polluted calcareous soil

Phytoremediation is a cleanup technology for the removal of contaminants from polluted soils. The influences of humic acid (HA) and four plant growth regulators, i.e. gibberellic acid, salicylic acid, 3-indoleacetic acid, and 6-benzylaminopurine on the phytoremediation of Pb by maize were investigated in a pot trial on a Pb-contaminated soil. Foliar spray of 6-benzylaminopurine and salicylic acid significantly increased mean root dry matter but none of growth regulators had a significant effect on that of shoot. Addition of HA decreased root dry matter and had no significant effect on that of shoots. Application of all growth regulators except gibberellic acid significantly increased root Pb uptake. Application of salicylic acid significantly increased mean uptake efficiency and shoot Pb concentration and uptake. Although addition of HA significantly increased mean phytoextraction and translocation efficiencies, these responses were mainly attributed to the role of HA in the reduction of both root dry weight and Pb uptake, meaning that HA is not promising in Pb phytoremediation by maize. Among the four plant growth regulators evaluated, salicylic acid was the most effective in enhancing phytoremediation through phytostabilization of Pb.     

Characterization of a flint maize (Zea mays L. convar. mays) Italian landrace: I. Morpho-phenological and agronomic traits

Maize (Zea mays L.) landraces have the highest genetic variation and adaptation to the natural and anthropological environment where they have evolved. Surveying both qualitative and quantitative morphological traits of existing landraces may be useful in maintaining their genetic diversity and preserving them from genetic erosion. Our research deals with the morpho-phenological and agronomic characterization of a flint maize landrace, named 'Nostrano di Storo', still grown in an inland hilly environment in the low valley of Chiese River in Trentino, North-Eastern Italy. The majority of plants from twenty field populations proved to belong, with few exceptions (NSt2, NSt9, NSt11), to a single population. It means that the plant material long grown in this area and maintained by local farmers through yearly selection forms a single landrace within which some populations (i.e. NSt1, NSt3, NSt4, NSt7, NSt10, NSt18, NSt19, NSt20) could be considered as most representative and taken as 'core'. This is supported by the fact that the genetic variability was much higher within than between field populations: half of the plant and ear traits investigated did not show any significant difference between populations whereas all traits but two showed highly significant differences within populations. Selection carried out over the years by each farmer according to his own criteria produced little genetic differentiation within the original population. Gene flow among farmer populations, most likely occurred through both pollen dispersion to neighboring cultivated fields and seed exchange among farmers, may help to explain the low genetic differentiation. This information is useful for both planning conservation and recognizing the landrace as a unique germplasm source of specific geographic origin.     

The influence on biosorption potentials of metal-resistant bacteria Enterobacter sp. EG16 and Bacillus subtilis DBM by typical red soil minerals

Journal of Soils and Sediments - Due to the inevitable interaction between bacteria and soil minerals, whether bacteria could exert the excepted functions in the soil is yet to be confirmed and how...     

Amelioration of water stress effects on wetland rice by urea-N,plant growth regulators,and foliar spray of a diazotrophic bacterium Klebsiella sp.

Some of the measures suggested for amelioration of drought effects include application of N fertilizer and plant growth regulators (PGRs). Since N₂-fixing bacteria produce plant growth substances (PGRs), the effect of foliar application of an active strain of Klebsiella sp. (KUPOS) on IR-50 rice was examined using three foliar sprays applied at 10-day intervals. Irrigation once every 3 days was essential for plant growth. Application of KUPOS and 40 kg N ha^-1 improved grain yield of acutely water stressed plants from 330 kg ha^-1 to more than 1300 kg ha^-1 along with an improvement in several growth variables and yield determinants. Indole acetic acid, kinetin and GA₃, in a mixture of 10^-4 M of each, were less effective than KUPOS in alleviating stress effects. The adverse effects of water stress on respiration and photosynthesis as indicated by CO₂ exchange were also alleviated by these treatments. While uptake of K, Mg, Ca, Fe and Mo was increased, Na content decreased, accompanied by an increase in proline content. The order of effectiveness of the treatments was 40 kg N ha^-1 >KUPOS>PGRs.     

Impact of plant genotype and nitrogen level on rice growth response to inoculation with Azospirillum sp. strain B510 under paddy field conditions

Abstract

Twenty rice cultivars, including three genetically-distinct groups (japonica, indica-1, and indica-2), were evaluated for their response to inoculation with Azospirillum sp. strain B510 in paddy fields with standard nitrogen (SN) and low nitrogen (LN) fertilization. In the SN field, the tiller numbers in most indica-2 cultivars, 37?days after transplanting (DAT), were significantly increased by the B510 inoculation, whereas those in 4 japonica cultivars were significantly decreased. A similar growth response was observed in the LN field, although the impacts of the B510 inoculation were more varied than in the SN field. At 58 DAT, the tiller numbers in most cultivars were lower or unaffected by the B510 inoculation under both SN and LN conditions, except that the tiller number of the Nipponbare cultivar, which is classified as japonica, was significantly higher in the LN field only. These results suggest that the effects of inoculation with Azospirillum sp. strain B510 on the growth of rice plants, especially on tiller numbers at the early growth stage, vary depending on the rice genotype, as well as nitrogen level. Therefore, the plant genotypes, growth stages, and fertilization managements must be considered when a plant-associated bacterium is evaluated for beneficial effects under field conditions.     

The phenological growth stages of Megacarpaea polyandra Benth. ex Madden: a high valued traditional medicinal plant of the Himalaya

Genetic Resources and Crop Evolution - Phenological studies of medicinal plants have been less explored especially for plants confined in the Himalayan region (India). Here we describe detailed...     

Synergistic effect of a tropical earthworm Balanteodrilus pearsei and velvetbean Mucuna pruriens var. utilis on maize growth and crop production

Many Mexican and Central American farmers use the legume cover crop Mucuna pruriens (velvetbean) to reduce weed growth, enhance soil fertility, and reduce the use of irrigation, tillage and herbicides. This cropping system can also maintain abundant native earthworm populations, such as of the endogeic species Balanteodrilus pearsei, although the functional significance of these earthworms, particularly their effects on litter decomposition and plant growth are still mostly unknown. Therefore, a completely randomized 2 × 2 factorial was set up to investigate the effects of B. pearsei and M. pruriens litter on maize growth under controlled conditions. One maize plant was grown in each bucket for 120 days and each treatment was replicated 10 times. Treatments consisted of: soil without B. pearsei and without M. pruriens residues (S); soil with B. pearsei and without M. pruriens litter (SB); soil with M. pruriens and without B. pearsei litter (SM); soil with B. pearsei and M. pruriens residues (SBM). In SBM, biomass, abundance and sexual maturity of B. pearsei were, respectively, 1.6, 1.4 and 2.4 times higher than in the treatment lacking M. pruriens (SB). B. pearsei presence significantly reduced the amount of M. pruriens litter mass remaining on the soil surface. Maize root biomass and grain yields were significantly higher in SBM than in SM, S and SB. Grain yield was significantly related to B. pearsei abundance and biomass, as well as to M. pruriens litter breakdown. The positive yields effects of SBM in this experiment appear to be due to a synergistic effect of B. pearsei and M. pruriens. These findings point to the importance of providing adequate conditions for earthworm activity in tropical agroecosystems, together with organic residue management, to enhance soil fertility, crop yields and agricultural sustainability.     

Rare earth elements and plant growth: I. Effects of lanthanum and cerium on root elongation of corn and mungbean.

Root elongation of corn (Zea mays cv. Hycorn 82) and mungbean (Vigna radiata cv. Berken) seedlings was measured in dilute complete nutrient solutions to which varying amounts of lanthanum (La) or cerium (Ce) had been added. The nutrient solutions were aged for 9 d prior to conducting the root elongation experiments and solution samples ultra‐filtered to 0.025 μm before chemical analyses for La or Ce, and phosphorus (P). Concentrations of La up to 10 μM and concentrations of Ce up to 8 μM remained in solution in the presence of 5 μM P at pH 4.5, but substantial losses of these elements and P occurred at pH 5.5. The relative root elongation of both plant species decreased with increasing concentrations of La or Ce in solution. Mungbean was much more sensitive than corn. Cerium was more toxic than La to mungbean, the concentrations associated with a 50% reduction in root elongation being 0.9 μM Ce and 3.1 μM La. Lanthanum was more toxic to corn than Ce, the concentrations corresponding to a 50% reduction in root elongation being 12.2 μM Ce and 4.8 μM La at pH 5.5, or 7.1 μM La at pH 4.5.     

Use of Trichoderma spp. and arbuscular mycorrhizal fungi to increase soil beneficial population of bacteria in a nectarine commercial orchard: Effect on root growth,nutrient acquisition and replanting disease

The aim of the present experiment was to evaluate the effect of commercial Trichoderma and arbuscular mycorrhizal fungi (AMF)-based bio-fertilizers on nectarine root growth, nutrient acquisition and replanting disease. The experiment was performed from 2008 to 2012 in an A. mellea-infected nectarine orchard subjected to the following treatments: 1) untreated control; 2) AMF-biofertilizer applied at planting (120 kg ha^?1) and every year in spring and autumn at the rate of 6 kg ha^?1; 3) Trichoderma spp applied at planting (5 g plant^?1) and every year (in April, May and September) at 2.5 kg ha^?1. AMF bio-fertilizers decreased root diameter and increased root survivorship. Leaf phosphorus concentration increased in AMF bio-fertilizers plots, while no significant treatments effects were observed on other leaf nutrient concentration. Although biofertilizer application did not affect soil microbial population, at the end of the trial (2012) the application of Trichoderma alone increased the population of the fungus.     

工厂化条件下氮处理对奶油生菜的生长及生理影响

通过水培试验研究不同氮处理(5 mmol·L~(-1)NO_3~--N、10 mmol·L~(-1)NO_3~--N和5 mmol·L~(-1)NO_3~--N+5 mmol·L~(-1)NH_4~+-N)对奶油生菜生长和生理特性的影响。研究结果表明,35 d后,总氮浓度相等时,NH_4~+-N抑制奶油生菜生长,该处理叶面积、株高、地上鲜重、地上干重、地下鲜重和地下干重分别降低78.2%、60.4%、87.0%、81.3%、80.1%和87.5%(P0.05),此外,两者的生理活性如根系活力、可溶性蛋白质、超氧化物歧化酶活性和硝酸还原酶活性均有显著性差异(P0.05)。与10 mmol·L~(-1)NO_3~--N(12.89 g)相比,5mmol·L~(-1)NO_3~--N(8.90 g)处理奶油生菜生物量稍微有所降低,叶面积、根长和地下干重分别降低48.1%、50.3%和37.5%(P0.05),而叶可溶性糖含量和花青素相对含量分别升高67.5%和51.9%(P0.05),而对NO_3~--N的吸收两者的比值在第21 d达到最大值,后者是前者的3.15倍。研究结果表明奶油生菜是喜硝蔬菜,且生菜的硝态氮适宜浓度前期(前21 d)为高浓度(10 mmol·L~(-1)),以便促进奶油生菜生长,后期(21 d后)可改为低浓度(5 mmol·L~(-1))以提高品质。     

Phosphorus fertilization of a grass-legume mixture: Effect on plant growth,nutrients acquisition and symbiotic associations with soil microorganisms

Adding P on Lotus tenuis and Festuca arundinacea, pure or mixed, on growth, nitrogen (N) and phosphorus (P) acquisition and associations with soil microorganisms was studied to investigate the establishment of Lotus for competing with Festuca. Triple-superphosphate was applied on a Typic Natraquoll where Lotus grows spontaneously. Biomass, N-P uptake, arbuscular mycorrhizal colonization and rhizobia nodulation were measured. Lotus achieved the highest biomass, N-P uptake in fertilized stands and Festuca the lowest in fertilized and non-fertilized stands. Mycorrhizal colonization decreased with P-fertilization in both plants. Rhizobia nodules in Lotus showed little changes with P-fertilization. In mixed fertilized-stands, Lotus promoted the growth, N-P uptake of Festuca. P-fertilization increases the ability of Festuca to compete with Lotus for available-P in soil. Lotus improves nutrient cycling, maintains high level of rhizobia nodules and arbuscular mycorrhizal colonization in roots. Adding P to limited N-P environments depress grasses growth to compete with legumes for resources.