Involvement of nitrate reductase-dependent nitric oxide production in magnetopriming-induced salt tolerance in soybean

In the present study, experiments were performed to investigate the role of nitric oxide (NO) in magnetopriming-induced seed germination and early growth characteristics of soybean (Glycine max) seedlings under salt stress. The NO donor (sodium nitroprusside, SNP), NO scavenger (2-[4-carboxyphenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, CPTIO), inhibitors of nitrate reductase (sodium tungstate, ST) or NO synthase (N-nitro-L-Arg-methyl ester, LNAME) and NADPH oxidase inhibitor (diphenylene iodonium, DPI) have been used to measure the role of NO in the alleviation of salinity stress by static magnetic field (SMF of 200 mT, 1 h). Salt stress (50 mM NaCl) significantly reduced germination and early growth of seedlings emerged from non-primed seeds. Pre-treatment of seeds with SMF positively stimulated the germination and consequently promoted the seedling growth. ST, LNAME, CPTIO and DPI significantly decreased the growth of seedling, activities of α-amylase, protease and nitrate reductase (NR), hydrogen peroxide (H₂O₂), superoxide (O₂^•−) and NO content in roots of seedlings emerged from non-primed and SMF-primed seeds. However, the extent of reduction was higher with ST in seedlings of SMF-primed seeds under both conditions, whereas SNP promoted all the studied parameters. Moreover, the generation of NO was also confirmed microscopically using a membrane permanent fluorochrome (4-5-diaminofluorescein diacetate [DAF-2 DA]). Further, analysis showed that SMF enhanced the NR activity and triggered the NO production and NR was maximally decreased by ST as compared to LNAME, CPTIO and DPI. Thus, in addition to ROS, NO might be one of the important signaling molecules in magnetopriming-induced salt tolerance in soybean and NR may be responsible for SMF-triggered NO generation in roots of soybean.     

Influence of magnetopriming on germination,growth, physiology,oil and essential contents of cumin (Cuminum cyminum L.)

An environment friendly technique is desirable for enhancing of crop production. In this study, seeds of cumin (Cuminum cyminum L.) Yazd accession were treated with 0, 150 mT, 250 mT, 500 mT and 1 T magnetic field strengths for min and germination parameters were determined. All of the treatments improved germination parameters and seedling growth as compared with the control. However, 500 and 150 mT were the most effective treatments and thus selected for field studies. Seeds were exposed to 150 mT and 500 mT static magnetic field of strengths for 12 min, planted in the field during 2010–2012 in Isfahan, Iran. Static magnetic field treatment shortened the days to emergence, flowering and maturity, increased chlorophyll and reduced proline contents. Highest biological, seed and essential oil yield, oil content, and oil yield were recorded under 500 mT followed by 150 mT and control, respectively. The results suggested that the pretreatment of cumin seeds with static magnetic field can improve germination, growth and oil and essential contents of the cumin seed under the field.     

STIMULATION OF GERMINATION IN RICE (ORYZA SATIVA L.) BY A STATIC MAGNETIC FIELD

This study evaluates the percentage and rate of germination of rice (Oryza sativa L.) seeds, when exposed to magnetic treatment in laboratory conditions. The seeds were exposed to 150 and 250 mT magnetic fields both chronically and for 20 min after seeding. Nonexposed seeds were used as control. Chronic exposure to a 150-mT magnetic field increased (p < 0.05) both the rate and percentage of germination relative to nonexposed seeds (18% at 48 h). Significant differences were also obtained for seeds exposed to a 250-mT magnetic field for 20 min (12% at 48 h). Additionally, seeds were moistened with water magnetically treated by static and dynamic methods. Dynamic and static treatment of water improved the germination of seeds related to the control, but significant differences (p < 0.05) were only obtained for the dynamic method (16% at 48 h).     

ALLELOPATHIC MECHANISMS OF VELVETLEAF (ABUTILON THEOPHRASTI MEDIC., MALVACEAE) ON SOYBEAN

Sampling in a soybean field established that presence of velvetleaf (A. theophrasti) weeds interfered with soybean production. Number of soybean pods and number of pods/stem were significantly lower in transect segments adjacent to velvetleaf plants. In bioassays for phytotoxicity of velvetleaf, several dilutions of aqueous extracts from fresh field-collected leaves depressed germination of radish seeds and inhibited growth of soybean seedlings. Seed germination bioassays from eluates of chromatograms developed in one dimension showed that two of three bands containing phenolic compounds were inhibitory to radish seed germination. Soybeans inhibited by aqueous velvetleaf extracts had increased diffusive resistance, suggesting partial stomatal closure. Inhibited plants also gave evidence of water stress, with leaf water potentials often as low as –20 bars and reduced water content, when compared with controls. Quantification of chlorophyll on a leaf area basis showed that chlorophyll of inhibited plants was below controls. These data demonstrate the allelopathic potential of velvetleaf and suggest that interference with water balance and chlorophyll content may be two mechanisms of inhibitory action of toxins present in the leaves of velvetleaf.     

Enhancement of germination, growth, and photosynthesis in soybean by pre-treatment of seeds with magnetic field

Experiments were conducted to study the effect of static magnetic fields on the seeds of soybean (Glycine max (L.) Merr. var: JS-335) by exposing the seeds to different magnetic field strengths from 0 to 300 mT in steps of 50 mT for 30, 60, and 90 min. Treatment with magnetic fields improved germination-related parameters like water uptake, speed of germination, seedling length, fresh weight, dry weight and vigor indices of soybean seeds under laboratory conditions. Improvement over untreated control was 5-42% for speed of germination, 4-73% for seedling length, 9-53% for fresh weight, 5-16% for dry weight, and 3-88% and 4-27% for vigor indices I and II, respectively. Treatment of 200 mT (60 min) and 150 mT (60 min), which were more effective than others in increasing most of the seedling parameters, were further explored for their effect on plant growth, leaf photosynthetic efficiency, and leaf protein content under field conditions. Among different growth parameters, leaf area, and leaf fresh weight showed maximum enhancement (more than twofold) in 1-month-old plants. Polyphasic chlorophyll a fluorescence (OJIP) transients from magnetically treated plants gave a higher fluorescence yield at the J-I-P phase. The total soluble protein map (SDS-polyacrylamide gel) of leaves showed increased intensities of the bands corresponding to a larger subunit (53 KDa) and smaller subunit (14 KDa) of Rubisco in the treated plants. We report here the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean.     

Effect of stationary magnetic field strengths of 150 and 200 mT on reactive oxygen species production in soybean

Our previous investigation reported the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean. In this study, soybean seeds treated with static magnetic fields of 150 and 200 mT for 1 h were evaluated for reactive oxygen species (ROS) and activity of antioxidant enzymes. Superoxide and hydroxyl radicals were measured in embryos and hypocotyls of germinating seeds by electron paramagnetic resonance spectroscopy and kinetics of superoxide production; hydrogen peroxide and antioxidant activities were estimated spectrophotometrically. Magnetic field treatment resulted in enhanced production of ROS mediated by cell wall peroxidase while ascorbic acid content, superoxide dismutase and ascorbate peroxidase activity decreased in the hypocotyl of germinating seeds. An increase in the cytosolic peroxidase activity indicated that this antioxidant enzyme had a vital role in scavenging the increased H(2)O(2) produced in seedlings from the magnetically treated seeds. Hence, these studies contribute to our first report on the biochemical basis of enhanced germination and seedling growth in magnetically treated seeds of soybean in relation to increased production of ROS.     

Influence of He−Ne laser irradiation of soybean seeds on seed mycoflora, growth, nodulation, and resistance toFusarium solani

Laser irradiation of soybean seeds for 3 min caused a clear reduction in the number of seed-borne fungi which became more pronounced as the irradiation time was extended. Pretreatment of the seeds with methylene blue, methyl red and carmine enhanced the effect of laser.Rhizoctonia solani, Alternaria tenuissima, Cercospora kikuchii andColletotrichum truncatum were completely eliminated when the seeds were pretreated with a dye and irradiated for 10 min. Seed germination was stimulated on exposure of the seed to 1-min irradiation. At such dose, most of the dyes were accelerators while the higher doses were inhibitory to seed germination. Chlorophylla, chlorophyllb and carotenoid content of developed plants differed, depending on the irradiation dose and dye treatment of the seeds. In seeds irradiated for 1 or 3 min, chlorophylla formation was less affected than chlorophyllb formation. In seeds irradiated for 10 min, both the chlorophyll contents were decreased especially in the presence of some applied dyes. On the other hand, there was an increase in carotenoid content of soybean leaves when the laser dose increased. The number and dry mass of nodules were mostly greater (as compared to the corresponding control), when the seeds irradiated for 1 or 3 min were pretreated with methyl red, chlorophenol red, crystal violet and methylene blue. Irradiation of pre-sowing seeds greatly protected soybean stands againstF. solani. The disease incidence differed somewhat when the irradiated seeds were pretreated with dyes. The reduction in disease incidence was accompanied by accumulation of high proline and phenol levels in the infected root tissues of soybean, suggesting that these compounds have a certain role in the prevention of disease development.     

Biostimulants Derived from Moroccan Seaweeds: Seed Germination Metabolomics and Growth Promotion of Tomato Plant

Polysaccharides extracted from seaweeds can function as plant biostimulants. The aim of this study was to assess the effects of Polysaccharide Enriched Extracts (PEEs) obtained from 17 Moroccan seaweeds, on tomato seed germination and plant growth. Three concentrations (0.02, 0.05 and 0.1 mg mL⁻¹) of PEEs were applied to tomato seeds to evaluate their effect on 3 germination parameters: germination percentage (GP), germination speed (GS) and mean germination time (MGT). Metabolomic analysis by GC–MS was subsequently performed on seedlings. In the second experiment, four PEEs concentrations (0.02, 0.05, 0.1 and 0.2 mg mL⁻¹) were used as foliar spray or as soil application to tomato plants. Their growth parameters (number of leaves, shoot length, fresh and dry weight of stem and roots) and biochemical parameters (chlorophyll a and b) were measured. Results indicated a significant increase of GP and GS associated with a significant reduction of MGT of tomato seeds treated with 0.02 mg mL⁻¹ of PEEs obtained from Gigartina sp., Gigartina pistillata, Chondracanthus acicularis, Gelidium crinale, Schizymenia dubyi, Cystoseira. foeniculacea and Fucus spiralis. Similar results were also obtained by application of higher PEEs concentration (0.1 mg mL⁻¹) extracted from Ulva rigida, Codium tomentosum, Codium decorticatum and Bifurcaria bifurcata. Metabolomic analysis on seedlings detected the presence of some metabolites which could possibly be involved in seed germination enhancement or inhibition. The results of the second experiment showed that the same PEEs cited above at the same concentrations enhanced plant dry weight and chlorophyll a content except Gigartina sp., C. foeniculacea and C. decorticatum. Furthermore, soil application of PEEs was more effective in improving plant growth parameters than foliar application. The study shows the potential of PEEs from Moroccan seaweed to be used as biostimulants for a sustainable agriculture.

     

NaCl胁迫下海滨锦葵种子萌发和幼苗生长过程的生理特性变化

以1／4 Hoagland溶液为基础培养液,研究了0．5％、1．0%、1．5％、2．0％和2．5％NaCl处理对海滨锦葵[Kostelezkya rirginica（L．）Presl．]种子萌发和幼苗生长的影响,发现随着培养液中NaCl浓度的增加,海滨锦葵种子萌发率逐渐降低;当NaCl浓度达2．5％时种子不萌发,但NaCl胁迫解除后,种子的萌发率水平与对照相当。幼苗在含0．5％～1．0%NaCl的培养液中生长状况良好,叶绿素含量和根系活力明显增高;但当NaCl浓度达1．5％-2．0％时,叶绿素含量和根系活力逐渐下降;与对照相比,NaCl胁迫下幼苗的MDA水平降低。结果表明,NaCl胁迫对海滨锦葵种子萌发和幼苗牛长有一定的影响,但海滨锦葵可通过种子休眠、增加根系活力、降低体内MDA水平来缓解一定的盐害效应．以适应盐胁迫的生长环境．     

Allelopathic Effects,Physiological Responses and Phenolic Compounds in Litter Extracts of Juniperus rigidaSieb. et Zucc.

The allelopathic effects of Juniperus rigida litter aqueous extract (LE) on wheat and Pinus tabuliformis were studied, as well as the physiological responses to the extract. High concentration LE (0.10 g Dw/ml) significantly inhibited the seed germination and seedling growth in receptor plants. The chlorophyll content and root activity in the wheat seedlings were reduced significantly across all treatments; however, those were more prominently reduced at high concentration (0.10 g Dw/ml) but received little stimulation at low concentration (0.025 g Dw/ml) in P. tabuliformis. The content of malonaldehyde (MDA) increased with increasing concentrations of LE, except at 0.025 g Dw/ml. Activities of antioxidant enzymes (POD, CAT and SOD) in receptor plants were all significantly inhibited at high concentrations but stimulated at low concentrations. These results demonstrate that the aqueous extract from J. rigida litter has allelopathic potential. Various phenolic compounds were identified in litter aqueous extract and litter ethanol extract by HPLC. The phenolic compound content in the aqueous extract was significantly lower than that in the ethanol extract. Chlorogenic acid and podophyllotoxin were the predominant phenolic compounds in both types of litter extracts. These findings suggest that the seed germination and seedling growth of P. tabuliformis and wheat would be inhibited when planted near large amounts J. rigida litter.     

Heat shock effects on seed germination of five Brazilian savanna species

Fire is considered an important factor in influencing the physiognomy, dynamics and composition of Neotropical savannas. Species of diverse physiognomies exhibit different responses to fire, such as population persistence and seed mortality, according to the fire frequency to which they are submitted. The aim of this study is to investigate the effects of heat shocks on seed germination of Anadenanthera macrocarpa (Benth.) Brenan, Dalbergia miscolobium Benth., Aristolochia galeata Mart. & Zucc., Kielmeyera coriacea (Spreng.) Mart. and Guazuma ulmifolia Lam., which are native species of the Brazilian savanna. The temperatures and exposure times to which the seeds were submitted were established according to data obtained in the field during a prescribed fire: 60 °C (10, 20 and 40 min), 80 °C (5, 10 and 20 min) and 100 °C (2, 5 and 10 min). Untreated seeds were used as controls. Seeds of A. galeata and K. coriacea showed high tolerance to most heat treatments, and seeds of A. macrocarpa showed a significant reduction in germination percentage after treatments of 80 °C and 100 °C. Treatments of 100 °C for 10 min reduced germination percentage for all species except G. ulmifolia, which has dormant seeds. For this species, germination was accelerated by heat treatments. The high temperatures applied did not interfere with the time to 50% germination (T₅₀) of the tolerant seeds. Seeds of the savanna species K. coriacea and A. galeata were more tolerant to heat shocks than seeds of the forest species A. macrocarpa. Guazuma ulmifolia, the forest species with seeds that germinate after heat shock, also occurs in savanna physiognomies. Overall, the high temperatures applied did not affect the germination rate of the tolerant seeds.     

Germination responses of <Emphasis Type="Italic">Erica andevalensis</Emphasis> to different chemical and physical treatments

Erica andevalensis Cabezudo & Rivera is a threatened edaphic endemic species of Andalusia (SW Spain). Under natural conditions, the plants produce a very large number of small seeds (0.3–0.4 mm) but very few seedlings survive. Different treatments (high temperature, cold pre-treatment, nitrogen salts, and gibberellic acid applications) were tested to assess germination patterns in different populations and to determinate the most favorable conditions for germination. Gibberellic acid was provided in five different concentrations from 0 to 400 ppm GA₃, while nitrogen was applied as 10 mM of either KNO₃ or NH₄NO₃. The effect of pH on germination was also tested. The species always showed a low germination rate (6.50–22%) that was not stimulated either by 1 or 4 months in dry cold pre-treatment, nitrogen application, acid pH medium, or by high temperature (80°C for 10 min); although gibberellic acid application (100–400 ppm) significantly enhanced germination. The highest percentage of germination (41.6%) was achieved with a mean germination time to start germination (t ₀) of 7.6 ± 0.54 days when the seeds were subjected to 400 ppm gibberellic acid treatment. The population origin did not have a significant effect on germination percentage.     

Characterisation of Soybean and Wheat Seeds by Nuclear Magnetic Resonance Spectroscopy

The effects of equilibration under different air relative humidities (RH, 1 – 90 %) and temperatures (35 and 45 °C) on soybean (Glycine max) and wheat (Triticum aestivum) seeds were studied using different techniques. Seed moisture content, electrical conductivity (EC) of seed leachate and per cent seed germination were measured following standard procedures, and compared with nuclear magnetic resonance spin-spin relaxation time (T₂) measurements. Moisture contents of soybean and wheat seeds, following the reverse sigmoidal trend, were greater at 35 than at 45 °C at any particular RH. Changes in T₂ were related to the changes in germination percentage and leachate EC of both soybean and wheat seeds. Equilibrating soybean seeds at RH 11 % decreased germination percentage with corresponding decrease in T₂. On the contrary, EC of seed leachate increased. In wheat seeds equilibrated at 45 °C, T² was maximal at RH 5.5 %. T₂ declined in seeds equilibrated at high RH (> 80 %) together with low germination percentage.     

Effect of the grass Leersia hexandra on the dispersal,seed germination,and establishment of Pachira aquatica seedlings

1. In wetlands, hydrochory is one of the main mechanisms of seed dispersal and there is often synchrony between propagule production and the flood season. Different sources of disturbance can prevent seed dispersal to suitable sites, and if environmental conditions are not adequate for germination and seedling establishment, recruitment will be limited, affecting succession.
2. We worked in a disturbed tropical freshwater swamp where the native grass Leersia hexandra has dominated open areas, creating a grass matrix that surrounds patches of swamp forest. Leersia grows vigorously, forming cushions of dry matter that cover the soil, forming a potential obstacle to seed dispersal. We asked whether the vegetative growth of this grass prevents the entry and dispersal of seeds of the tropical swamp tree Pachira aquatica, thwarting seed germination and seedling establishment, and arresting succession. We set up transects in the grass matrix in two zones: close to the river (R) and bordering the tree patches or fragments (F). We quantified tree seed and seedling presence, survival and growth in situ and experimentally introduced seeds and seedlings in the field and monitored seed germination and the survival and growth of their seedlings, as well as that of transplanted seedlings.
3. There was a negative relationship between the number of seeds and established seedlings, and the distance to river or fragment (r = −0.86, p < 0.001 for zone R; and r = −0.77, p < 0.001 for zone F) and with the grass cushion (r = −0.68, p = 0.005 for zone R; and r = −0.66, p = 0.007 for zone F); the grass creating a barrier to dispersal. When seeds were sown after clearing the grass cushion, germination success was high, so this stage is not limited. The transplanted seedlings had better survival and a greater final height than the seedlings of the sown seeds. Grass cover had a negative effect on both types of seedlings. Seedling survival rates were inversely related to grass cover, showing that seedlings overgrown by grass had low survival rates. Flooding is a stress factor for seedlings and produced mortality, in addition to the effects of the grass.
4. Together, the field survey and the experiment show that succession is being arrested in two ways: (1) by limiting seed dispersal because the grass cushion slows the dispersal and penetration of seeds into the vegetation; and (2) by limiting seedling establishment because the grass competes for space and light. Our results show that even where the grass is native, slower growing, seed-dependent species may struggle to compete and establish. If grass cover is increasing, these swamps are very vulnerable to a decrease in area because it is very difficult for them to regenerate naturally.

     

Increased motor activity of the beetle Laemostenus punctatus caused by a static magnetic field of 110 mT

The aim of this study was to investigate the effects of a static magnetic field on six behavioral parameters (travel distance, average speed while in motion, travel distance of the head, body rotations, time in movement, and immobility time) of the ground beetle Laemostenus (Pristonychus) punctatus (Dejean) (Coleoptera: Carabidae). Adults of this troglophilic and guanophilic beetle were randomly divided into two groups, the first exposed to a static magnetic field of 110 mT for 5 h, and the second a control group. Beetle behavior after these 5 h was monitored in an open‐field test for 12 min and analyzed using ANY‐maze software. Exposure to a static magnetic field of 110 mT increased motor activity (travel distance and average speed while in motion) in the first 4 min. After that there were no significant differences. We conclude that the applied static magnetic field affects motor activity of adult specimens of L. (P.) punctatus, and we discuss the mechanism, possibly through acting on the control centers responsible for orientation and movement.     

Effects of neodymium magneto-priming on seed germination and salinity tolerance in tomato

Earth's biosphere is surrounded by magnetic fields that affect all living organisms. A plant's response to magnetic fields is displayed in terms of its seed's vigor, growth, and yield. Examining seed germination in such magnetic fields is the first step in the investigation of how magnetic fields might be used to enhance plant growth and maximize crop performance. In this study, salinity-sensitive Super Strain-B tomato seeds were primed with the northern and southern poles of neodymium magnets of 150, 200, and 250 mT. The magneto-primed seeds showed a significant increase in germination rate and speed, where the orientation of the magnet was identified as being crucial for germination rate and the orientation of seeds towards the magnet was shown to affect the germination speed. The primed plants exhibited enhanced growth characteristics, including longer shoots and roots, larger leaf area, more root hairs, higher water content, and more tolerance to salinity levels, up to 200 mM NaCl. All magneto-primed plants showed a significant decrease in chlorophyll content, continuous chlorophyll fluorescence yield (Ft), and quantum yield (QY). The salinity treatments decreased all chlorophyll parameters in control plants, significantly, but did not lower such parameters in magneto-primed tomatoes. The results of this study illustrate the positive effects of neodymium magnet on the growth and development of tomato plants in terms of their germination, growth, and salinity tolerance, and negatively affected the chlorophyll content in tomato leaves. © 2023 Bioelectromagnetics Society.     

Effects of Jasmonic Acid on Groundnut During Early Seedling growth

Exposure of groundnut seeds and seedlings to 25, 100, and 250 μM concentrations of jasmonic acid resulted in a reduction of germination percentage, growth, fresh mass, dry mass, chlorophyll content, chlorophyll stability index, proteins and an increase in free proline content and cell membrane injury. The results suggest the inhibitory effect of jasmonic acid on growth of the groundnut seedlings. This revised version was published online in July 2006 with corrections to the Cover Date.     

Water-soluble phenolic compounds in the coat control germination and peroxidase reactivation in <Emphasis Type="Italic">Triticum aestivum</Emphasis> seeds

In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid equivalent g⁻¹ dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1% H₂O₂ reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H₂O₂ pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated. Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation.     

Allelopathic and intraspecific growth competition effects establishment of direct sown Miscanthus

High yielding perennial crops are being developed as a sustainable feedstock for renewable energy and bioproducts. Miscanthus is a leading biomass crop, but most plantations comprise a sterile hybrid Miscanthus × giganteus that is clonally propagated. To develop new varieties across large areas, rhizome cloning is inefficient, time consuming and expensive. Alternative approaches use seed, and in temperate regions, this has been successfully applied by raising seedlings as plug plants in glasshouses before transfer to the field. Direct sowing has yet to be proven commercially viable because poor germination has resulted in inconsistent stand establishment. Oversowing using seed clusters is a common approach to improve the establishment of crops and it was hypothesized that such an approach will improve uniformity of density in early Miscanthus stands and thereby improve yield. Sowing multiple seeds creates potential for new interactions, and we identified at least two inhibitory mechanisms related to seed numbers. Germinating seed produced allelopathic effects on nearby seed thereby inhibiting plant growth. The inhibitory effect of Miscanthus seed on germination percentages was related to seed number within clusters. An extract from germinating Miscanthus seed inhibited the germination of Miscanthus seed. The extract was analysed by HPLC, which identified a complex mixture including several known allelopathic compounds including proanthocyanidins and vanillic acid. There was also evidence of root competition in soil in a controlled environment experiment. When the experiment on competition was replicated at field scale, the establishment rates were much lower and there was evidence of shoot competition. We conclude that the numbers of seed required to ensure an acceptable level of establishment in the field may be economically impractical until other agronomic techniques are included either to reduce the inhibitory effects of higher seed numbers or to reduce oversowing rates.     

根瘤菌对广金钱草种子萌发及幼苗生长的影响

为探求促进广金钱草萌发及生长的有效途径,该文使用不同浓度的费氏中华根瘤菌、放射型根瘤菌以及田菁茎瘤固氮根瘤菌菌液分别浸染广金钱草种子,以蒸馏水浸泡种子为空白处理,研究其对广金钱草种子萌发指标(发芽率、发芽势、发芽指数、活力指数)的影响,并在温室培养40、60、80 d后分别测定广金钱草幼苗的生长指标(叶片数、分枝数、株高)及部分生理指标(叶绿素含量、含氮量)的变化。结果表明:(1)在1×10⁷ CFU·mL^-1浓度条件下,三种菌液浸种均获得最大萌发指标,其中田菁茎瘤固氮根瘤菌实验组效果最显著,发芽率、发芽势、发芽指数和活力指数高于对照组16.00%、9.33%、9.51和41.34%。(2)除田菁茎瘤固氮根瘤菌实验组外,其余实验组的广金钱草幼苗叶片数、分枝数及株高均低于对照组。(3)放射型根瘤菌实验组和田菁茎瘤固氮根瘤菌实验组幼苗叶绿素含量相比对照组分别增加1.47%和7.47%,含氮量分别增加0.57%和5.17%。综上所述,三种根瘤菌菌液浸种均可在不同程度上提高广金钱草种子的发芽能力和植株生长期的叶绿素和含氮量,其中田菁茎瘤固氮根瘤菌具有最大正向影响,可有效提高种子萌发能力并促进植株生长。该研究可为不同地区广金钱草的种植和栽培提供技术指导,为开发田菁茎瘤固氮根瘤菌作为植物促生长菌剂提供理论支持。