Effects of crop residues,soil type and temperature on emergence and early growth of wheat

Summary Two controlled environment experiments were conducted to examine the germination and early growth of wheat (Triticum aestivum L. cv. Songlen) growing under crop residues of rape, sorghum, field pea and wheat. Additional treamments also included were soil type (Lithic Vertic Ustochrept and Plinthustalf) and temperature (8°C and 24°C to simulate winter and autumn sowing conditions). At low temperature, wheat and sorghum residues produced the most adverse effects on germination with all residues reducing emergence at high temperatures. Shoot lengths were also reduced by most residues at high temperatures whilst root lengths and shoot and root dry weights were unaffected by residue treatments. These results suggest major phytotoxic effects of residues during early growth (up to 14 days after sowing) with, in general, few interactions with soil type or temperature.     

不同基因型春小麦对磷胁迫适应性研究

采用盆栽试验,测定了4种基因型春小麦在不同生育期,3种磷水平下植株体内酸性磷酸酶活性、根长、根半径、根干重、根冠比、地上部干重、产量等指标,研究了小麦生长对磷素的利用效率。结果表明：甘春20号对磷素的敏感性在酸性磷酸酶活性、根干重、地上部干重、增产潜力均强于陇春16号、会宁18号和定西33号,是磷高效基因型;高磷对陇春16号的根冠比和根干重影响显著,定西33号和会宁18号的根长较长,因此陇春16号、会宁18号和定西33号仍具有一定的磷素利用潜势。     

Impact of soil stockpiling on ericoid mycorrhizal colonization and growth of velvetleaf blueberry (Vaccinium myrtilloides) and Labrador tea (Ledum groenlandicum)

Soil stockpiling is a common practice prior to the reclamation of surface mines. In this study, velvetleaf blueberry and Labrador tea plants were grown from seed in fresh soil, stockpiled soil (1 year), and autoclaved stockpiled soil (1 year) obtained from the Canadian boreal forest. After 7 months of growth, the root colonization intensity with ericoid mycorrhizal (ERM) fungi in both plants growing in stockpiled soil was lower compared to plants growing in the fresh soil. The diversity of ERM fungal species in roots also decreased due to soil stockpiling and Pezoloma ericae was absent from the plants growing in stockpiled soil. Changes in the ERM root colonization in plants growing in stockpiled soil were accompanied by decreases in root and shoot dry weights. Leaf chlorophyll, nitrogen, and phosphorus concentrations of velvetleaf blueberry were higher in fresh soil compared to 1‐year stockpiled soil. Plants grown in the autoclaved stockpiled soil became colonized by the thermotolerant ERM fungus Leohumicola verrucosa and showed higher root and shoot biomass compared to the nonautoclaved stockpiled soil. The results point to the importance of ERM fungi for growth of ericaceous plants, even under favorable environmental conditions and adequate fertilization, and suggest that reduced ERM colonization intensity and ERM fungal diversity in roots likely contributed to the negative effects of soil stockpiling on growth of velvetleaf blueberry and Labrador tea.     

Isolation and characterization of bacteria from the rhizosphere of wheat

In this study, we isolated bacteria from rhizosphere and endorhizophere of wheat crops of the central region of Argentina. The isolates were phenotypically characterized and the restriction patterns of 16S rDNA (ARDRA) using endonuclease AluI were analysed. Representative isolates were used to evaluate the effect of the inoculation on the growth of wheat under greenhouse conditions. The effects of plant growth-promoting bacteria on wheat plants were studied by evaluating shoot fresh and dry weights and root fresh and dry weights. One native strain increased the shoot and root dry biomass by 23% and 45% respectively. Other strains increased the shoot dry biomass. A 1.5 kb fragment of the 16S rRNA gene of one isolate was sequenced. This isolate showed high identity with different species of Pseudomonas.     

Performance of established native seedlings in relation to invasive Lantana camara, rainfall and species’ habitat preferences in a seasonally dry tropical forest

Native species’ response to the presence of invasive species is context specific. This response cannot be studied in isolation from the prevailing environmental stresses in invaded habitats such as seasonal drought. We investigated the combined effects of an invasive shrub Lantana camara L. (lantana), seasonal rainfall and species’ microsite preferences on the growth and survival of 1,105 naturally established seedlings of native trees and shrubs in a seasonally dry tropical forest. Individuals were followed from April 2008 to February 2010, and growth and survival measured in relation to lantana density, seasonality of rainfall and species characteristics in a 50-ha permanent forest plot located in Mudumalai, southern India. We used a mixed effects modelling approach to examine seedling growth and generalized linear models to examine seedling survival. The overall relative height growth rate of established seedlings was found to be very low irrespective of the presence or absence of dense lantana. 22-month growth rate of dry forest species was lower under dense lantana while moist forest species were not affected by the presence of lantana thickets. 4-month growth rates of all species increased with increasing inter-census rainfall. Community results may be influenced by responses of the most abundant species, Catunaregam spinosa, whose growth rates were always lower under dense lantana. Overall seedling survival was high, increased with increasing rainfall and was higher for species with dry forest preference than for species with moist forest preference. The high survival rates of naturally established seedlings combined with their basal sprouting ability in this forest could enable the persistence of woody species in the face of invasive species.     

Improvement of drought tolerance of soybean plants by using methyl jasmonate

Methyl jasmonate (MeJA) is a naturally occurring plant growth regulator and play vital roles in plant defense and many developmental processes such as root growth and seed germination. This study was undertaken to study the possible role of using methyl jasmonate to alleviate the adverse effect of water stress on soybean genotypes (Giza 22 and 35). The results showed that water stress reduced shoot length, fresh and dry weights of shoot and root, photosynthetic pigments, relative water content and oil content in the shoots of all soybean genotypes. On the other hand, there was a considerable increase in cell wall fractionation, saturated and unsaturated fatty acids, flavonoids, phenolic acid and sugar fraction content in the shoots of the soybean genotypes in response to the water stress. Foliar spray with methyl jasmonate increased all the above parameters as compared to stressed plants. The results investigate the important role of MeJA in alleviation of water stress in soybean plants and suggest that MeJA could be used for improving plant growth under water stress as a potential growth regulator. The soybean genotypes Giza 22 was found to be more resistant to water stress than Giza 35.     

The porous-membrane technique for root studies of field-grown crops

A porous-membrane technique has been successfully used in root studies of field-grown soybean,Glycine max L. Merr., for several years. In order to evaluate this technique on other crops, a study was conducted to compare growth parameters of individual soybean, cotton,Gossypium hirsutum L., and corn,Zea mays L., plants grown with and without their root systems confined within porous membranes. Results indicate that plant species respond differently to root confinement.Root confinement reduced all shoot growth and yield parameters of the crop species, however the reduction was generally greatest for cotton. Apparently, cotton is less adaptable to the restricted rooting volume. Root confinement reduced levels of potassium and phosphorus in soybean and nitrogen in corn and cotton. Fertilizer rates higher than soil test recommendations should be applied to membrane-grown plants to prevent reductions in nutrient levels. It may be possible that modifying the size or shape of the membrane may enhance root and shoot growth of specific crop plants like cotton and increase the ability of this technique to be used on a broader spectrum of crop plants.     

Effect of imazapic residues on photosynthetic traits and chlorophyll fluorescence of maize seedlings

The influence of various concentrations of imazapic residues (0–800 μg kg^–1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection.     

Some aspects of wheat cultivar response to applied phosphate

Summary Two experiments are described in which a comparison was made of differences in phosphorus contents, dry matter production and root growth between a semi-dwarf wheat (Israel M68) and a standard height cultivar (Olympic). In the first experiment, using soil as a support medium, Olympic had higher root dry weight and root to shoot ratios, but lower root and shoot phosphorus contents, than Israel M68. In the second experiment, using solution culture technique, Olympic had higher root dry weights and root to shoot ratios, but there was no cultivar difference in either root or shoot phosphorus content. This suggests an improved ability in the semi-dwarf wheat to explore the soil system. In both experiments the rate of uptake of phosphorus, when calculated per unit root fresh weight, was highest with Israel M68. Root measurements in a later experiment (Experiment 2a) indicated similar total fresh weights for both cultivars, but on a unit fresh weight basis, the semi-dwarf cultivar had a greater root number, root area and lateral root volume. Although further studies to clarify the situation are necessary, these differences may be associated with the enhanced grain yield response to superphosphate of some semi-dwarf wheats when compared to standard height cultivars. re]19751104     

The growth, yield and nutrient uptake of winter wheat following root-pruning

The effect of root-pruning on shoot growth was investigated in winter wheat growing in lysimeters. Removal of half of the root axes at the beginning of stem elongation reduced shoot dry matter, determined 1 month after pruning, by 13% and grain yield by 8%. Removal of either the seminal or nodal root system during tillering reduced shoot dry weight, measured during the growing season, by 7% and grain yield by 25%. Root-pruning had negligible, or only transient, effects on the concentration of nitrogen, phosphorus, potassium, magnesium and manganese in the shoots. The harvest index was not affected by root-pruning.     

Growth dynamics of root and shoot hydraulic conductance in seedlings of five neotropical tree species: scaling to show possible adaptation to differing light regimes

The dynamics of growth (shoot and root dry weights, surface areas, hydraulic conductances, and root length) were measured in seedlings of five neotropical tree species aged 4–16 months. The species studied included two light-demanding pioneers (Miconia argentea and Apeiba membranacea) and three shade-tolerant young- or old-forest species (Pouteria reticulata, Gustavia superba, and Trichilia tuberculata). Growth analysis revealed that shoot and root dry weights and hydraulic conductances and leaf area all increased exponentially with time. Alternative methods of scaling measured parameters to reveal differences that might explain adaptations to microsites are discussed. Scaling root conductance to root surface area or root length revealed a few species differences but nothing that correlated with adaptation to light regimes. Scaling of root surface area or root length to root dry weight revealed that pioneers produced significantly more root area and length per gram dry weight investment than shade-tolerant species. Scaling of root and shoot hydraulic conductances to leaf area and scaling of root conductance to root dry weight and shoot conductance to shoot dry weight also revealed that pioneers were significantly more conductive to water than shade-tolerant species. The advantages of scaling hydraulic parameters to leaf surface area are discussed in terms of the Ohm's law analogue of water flow in plants. Received: 24 March 1997 / Accepted: 17 November 1997     

Growth,abscisic acid content,and carbon isotope composition in wheat cultivars grown under different soil moisture

Changes in dry matter accumulation and allocation, abscisic acid content and carbon isotope composition of three wheat cultivars from dry, middle and wet climate regions were recorded at full maturity after exposure to different watering regimes (100, 50 and 25 % field capacity). Compared with the wet climate cultivar, the dry climate cultivar showed lower stem height, total leaf area, total dry biomass and total grain dry mass, and higher root/shoot ratio, abscisic acid content and carbon isotope composition under all watering regimes. Both water-limited treatments significantly reduced leaf growth and increased dry matter allocation into the roots leading to a significant raise of root/shoot ratio in all cultivars tested. In addition, drought affected morphological and physiological properties more in the dry climate cultivar than in the wet climate cultivar.     

Differential Rhizosphere Establishment and Cyanide Production by Alginate-Formulated Weed-Deleterious Rhizobacteria

The effects of Pseudomonas putida ATH2-1RI/9 and Acidovorax delafieldii ATH2-2RS/1 on rhizosphere colonization, cyanide production, and growth of velvetleaf and corn was examined. When formulated in alginate beads and inoculated onto velvetleaf and corn plants (10⁹ CFU/plant), only P. putida ATH2-1RI/9 consistently reduced velvetleaf growth. Neither isolate inhibited corn growth. Interestingly the levels of P. putida ATH2-1RI/9 in the velvetleaf rhizosphere were 1000-fold higher (7 × 10⁷ CFU/g root) than the A. delafieldii ATH2-2RS/1 populations. Cyanide (53–68 mM/g root) was recovered from the P. putida ATH2-1RI/9-inoculated velvetleaf plants. In contrast both A. delafieldii ATH2-2RS/1 and P. putida ATH2-1RI/9 colonized the corn rhizosphere to the same extent (1–5 × 10⁷ CFU/g root), producing 1 mM and 14 mM/g root respectively. These results suggest that bacterial formulation methods can influence the effectiveness of deleterious rhizobacteria in reducing weed growth.     

多裂骆驼蓬中生物碱类物质对小麦种子萌发和幼苗生长的影响

室内培养和盆栽试验结果表明,多裂骆驼蓬生物碱提取液浸种的小麦萌发种子呼吸速率、淀粉酶和蛋白酶活性受抑,种子萌发率下降并随处理浓度提高而降低。幼苗根系活性和叶绿素含量提高,叶片硝酸还原酶（NR）、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性增强,过氧化氢酶（CAT）活性下降;幼苗根体积,株高、根系和地上部干重增加。多裂骆驼蓬生物碱提取液浸种对小麦种子萌发和幼苗生长作用的大小顺序为：总生物碱〉水溶性生物碱〉脂溶性生物碱。     

Phosphorus and intraspecific density alter plant responses to arbuscular mycorrhizas

We investigated how phosphorus availability, intraspecific density, and their interaction affect plant responses to arbuscular mycorrhizas. Four facultatively mycotrophic species: chile, cilantro, tomato, and corn were examined separately in pot experiments that employed a tropical phosphorus-immobilizing soil. Each experiment comprised nine soluble phosphorus additions, two levels of intraspecific plant density, and inoculation with arbuscular mycorrhizal fungi or not. High phosphorus signi- ficantly diminished mycorrhizal colonization of corn, cilantro, and tomato, but not chile, which was highly variably colonized. Corn roots were colonized by other root-inhabiting fungi, and mycorrhizas significantly reduced colonization by these potential root parasites. High phosphorus significantly increased relative growth rates (RGR) of all species, and high density significantly reduced RGR of cilantro, tomato, and corn. Chile showed little growth at any but the highest phosphorus additions, and consequently had no RGR response to density or mycorrhizas. Mycorrhiza inoculation caused transient depression of corn growth during the first month, but mycorrhizas increased corn RGR during the second month of growth. Both RGR and dry weights at harvest, cilantro, tomato, and corn benefited from mycorrhizas at low phosphorus availability, but this benefit diminished or changed to disadvantage as phosphorus availability increased. At low phosphorus availability, high density increased the dry weight of mycorrhizal cilantro and thereby amplified the benefit of mycorrhizas. At high phosphorus availability, increased density diminished the effects of mycorrhizas on dry weight, reducing mycorrhiza benefit to tomato and chile and reducing mycorrhiza detriment to cilantro. This study demonstrates that for three of the four plant species examined, phosphorus availability, intraspecific density, and their interaction significantly modify plant responses to arbuscular mycorrhizas.     

东北地区不同小麦品种对黑麦草的化感作用

以东北地区33个不同来源的小麦品种为研究对象,采用琼脂共培法,评价了不同小麦品种对黑麦草所产生的化感作用.通过分析不同小麦品种对黑麦草根长、苗高、根干重及苗干重的影响,探讨不同小麦品种对黑麦草化感作用的差异,从而筛选出具有较强化感潜力的小麦品种.结果表明,不同小麦品种对黑麦草根长、苗高、根干重及苗干重的影响存在显著差异.利用RI值作为化感作用的指标,结合聚类分析方法,可将这33个小麦品种按化感能力的强、中、弱分成3类;其中龙幅麦9号、龙幅麦13号、锦麦2003和小冰麦33号为化感能力较强的品种.     

两种羟基苯乙酸对大豆萌发的化感效应研究

通过田间和室内试验相结合,利用高效液相色谱检测大豆根际土境和残茬腐解液中的对羟基苯乙酸和间羟基苯乙酸的含量;在培养皿内研究两种酚酸对大豆生长抑制效应;研究了二者对大豆DNA熔点(Tm)的影响,并采用SDS—PAGE方法研究二者对根系蛋白合成的影响．结果表明,在大豆根际土境和残茬腐解液中检测到对羟基苯乙酸;两种羟基苯乙酸处理后,大豆例根效和主根长均显著减少,表现出明显的化感抑制效应,间羟基苯乙酸的抑制效应更明显;两种羟基苯乙酸使大豆DNA的熔点(Tm)下降,一些小分子蛋白的合成受到影响,从而抑制大豆生长,表现出典型的化感效应。     

Biology and Pathogenicity of Pratylenchus neglectus on Alfalfa

Pratylenchus neglectus reduced the growth of alfalfa cultivars in greenhouse and growth chamber studies. Inocula (1,000, 5,000 and 10,000 nematodes per plant) reduced shoot dry weights of Ranger by 16, 27, and 40%, of Lahontan by 16, 32, and 40%, and of Nevada Synthetic XX (Nev Syn XX) by 18, 26, and 37%, respectively, at 26 ñ 2 C. Pratylenchus neglectus at 1,000 nematodes per plant reduced Ranger shoot dry weights by 5, 12, 18, and 27%, at 15, 20, 25, and 30 C, respectively, whereas 5,000 nematodes per plant reduced shoot dry weights by 12, 17, 26, and 38%, respectively, at similar temperatures. Reductions in dry root weights were directly related to reductions in shoot growth. At 1,000 nematodes per plant, Ranger root dry weights were reduced by 3, 14, 40, and 40%, whereas 5,000 nematodes per plant reduced root dry weight by 25, 31, 59, and 63%, respectively, at similar temperatures. Similar results were observed on Lahontan and Nev Syn XX at the same inoculum levels and soil temperatures. Nematode reproductive indices (final nematode population per plant divided by initial nematode inoculum per plant) were higher at 1,000 nematodes per plant than at 5,000 nematodes per plant, were positively correlated with temperature, and were unaffected by cultivar.     

Comparative greenhouse study of Eucalyptus grandis in vitro plantlets and half-sib seedlings,II. Dry matter accumulation and relative distribution

In vitro directly micropropagated plantlets from three selected five-year-old Eucalyptus grandis Hill ex. Maiden hybrids were compared to their related half-sib seedlings for growth and growth pattern parameters under greenhouse conditions used for operational seedling production. The oven dry weights were determined from stem, leaf, and root samples collected every 40 days for four times. Relative growth rate, net assimilation rates and shoot:root ratio were calculated. Survival was 98% and 95% for plantlets and seedlings, respectively. Significant differences were observed between parents in terms of shoot and root dry weights and their ratios with similar ranking among plantlets and seedlings, suggesting genetic control over these traits. Plantlets started with significantly higher root: shoot ratios and stem, leaf, root, and total dry weight. Although seedlings had higher relative growth and net assimilation rates, all the initial differences decreased sharply over time.     

Effect of soybean plant growth on spore production byGlomus mosseae

Plants of two soybean cultivars infected withGlomus mosseae were physiologically stressed by top removal and were harvested at seven bi-weekly intervals. Removing tops stopped root growth, stimulated branching, delayed plant growth stages by approximately two weeks, but did not affect spore production. Spore numbers were significantly related only to time of harvest. Pot variation in spore number was not significantly correlated with infection percentage or root dry weight. Harvest, cultivar, and cutting effects were highly significant for root and shoot weights and root/shoot ratios.Approved by the Director as a contribution from the Missouri Agricultural Experiment Station (Journal Series No. 8123).