The comparative phosphorus requirements of some temperate perennial legumes

The phosphorus (P) responses of seven temperate perennial pasture legumes and two species of lupins were compared in a field trial over a range of nine P rates, from 0 to 800 kg ha^-1. The two lupins produced more than 5 t ha^-1 of dry matter in the absence of added P and showed no response to the fertiliser. In contrast, the pasture legumes initially failed to grow without added P and responded to applications of between 200 and 800 kg ha^-1. At the higher rates of P, dry matter production of the pasture legumes was equivalent to that of the lupins.In the first 2 years of the trial; the most productive pasture legume species at the higher rates of added P were also the most productive at the lower rates. Phosphorus requirements for 90% of maximum yield varied greatly between species, but were closely related to maximum yield. Thus species with low P requirements for maximum yield were not necessarily P-efficient species. In the third and subsequent years of the trial Lotus corniculatus performed better than the other pasture legumes at the lower rates of added P. In contrast to other studies Lotus pedunculatus showed no ability to outyield Trifolium repens at low rates of P. Critical P concentrations of the pasture species for the late spring-early summer period declined in the order Trifolium repens (0.34%) > Lotus pedunculatus (0.30%) > Triofolium pratense (0.28%) > Trifolium hybridum (0.27%) > Trifolium ambiguum (0.26%) > Lotus corniculatus (0.23%).Mineralisable nitrogen (N) levels were determined in soils under three species in the 7th year of the trial. At the lowest rates of added P, mineralisable N levels were much higher under Lupinus polyphyllus than under Trifolium repens or Lotus corniculatus. With increasing P rate, levels under the latter species increased, and at 100 kg P ha^-1 were equivalent to those under the lupin with no added P.     

Nitrogen fixation by white clover when competing with grasses at moderately low temperatures

It was the aim of this study to determine the way in which low temperature modifies the effect of a competing grass on nitrogen fixation of a forage legume. White clover (Trifolium repens L.) was grown in monoculture or in different planting ratios with timothy (Phleum pratense L.) or perennial ryegress (Lolium perenne L.) in growth chambers at either 7.5/5°C (LoT) or 15/10°C (HiT) average day/night temperatures, and with 2.5 or 7.5 mM ¹⁵N-labelled nitrate in the nutrient solution.Competition with grass led to a marked increase in the proportion of clover nitrogen derived from symbiosis (% N_sym). This increase was slower at LoT where % N_sym was reduced considerably; it was closely related to the reduction in the amount of available nitrate as a result of its being utilized by the grass.Nitrogen concentration in white clover herbage and dry matter yield per clover plant were reduced, for the most part, when a competing grass was present. The amount of nitrogen fixed per plant of white clover decreased markedly with temperature. Low temperature consequently accentuated competition for nitrate. The capacity of white clover to compete successfully was limited by its slower growth and nitrogen accumulation.     

Seasonal distribution of topsoil ammonium and nitrate under legume-grass and grass swards

Losses of soil N through leaching and N₂ fixation by legumes often are related to soil nitrate concentration. The seasonal distribution of soil ammonium and nitrate concentrations under ungrazed legume-grass and grass swards were evaluated on two experiments that were established in 1983 (Exp. 1) and in 1984 (Exp. 2). Treatments were white clover (Trifolium repens L.) (WC), red clover (Trifolium pratense L.) (RC), and birdsfoot trefoil (Lotus corniculatus L.) (BT), each grown with tall fescue (Festuca arundicacea Schreb.) (TF) at two legume proportions, and a pure stand of TF. The concentrations of both forms of N were measured in the top 20-cm layer during 2 years in Exp. 1 and for 1 year in Exp. 2. The concentrations of nitrate and ammonium were least in winter and spring, and greatest in summer. The concentration of nitrate for the mixtures decreased in the order WC-TF, RC-TF, and BT-TF in both summers of Exp. 1 but there were no mixture differences in Exp. 2. The concentration of soil ammonium was not affected by the treatments applied. We conclude that the concentration of soil nitrate usually was small for these swards but became greater and often dependent on species and legume proportion during summer. The concentration of soil ammonium also was greater in summer but was not affected by species or legume proportion. Journal of Paper no. J.-13359 of the Iowa Agric. and Home Econ. Exp Stn., Ames. Project 2281. Supported in part by the Facultad de Agronomía, Montevideo, Uruguay. Journal of Paper no. J.-13359 of the Iowa Agric. and Home Econ. Exp Stn., Ames. Project 2281. Supported in part by the Facultad de Agronomía, Montevideo, Uruguay.     

Chemical defense production in Lotus corniculatus L. I. The effects of nitrogen source on growth,reproduction and defense

Summary The carbon to nitrogen balance theory was examined for a legume, Lotus corniculatus L., which allocates carbon to nitrogen fixation. N-fixation can influence the ratio of carbon to nitrogen in legumes by providing nitrogen in nutrient-poor habitats, and by consuming carbon for support of symbiotic N-fixation. L. corniculatus clones (genotypes) were grown under two levels of nitrogen fertilization: a treatment which suppressed nodulation with fertilization and a treatment which received no additional fertilization. These plants relied solely on symbiotic N-fixation. Plants which supported symbionts had lower biomass and lower tannin concentrations than fertilized plants; this appears to be a result of the large carbon demand on N-fixation. Plants supporting symbionts often had relatively lower protein concentrations than fertilized plants. Cyanide concentration was influenced by plant genotype but not by nitrogen source. Although symbiotic N-fixing plants were smaller, they had three times the reproductive output of fertilized plants.     

Investigations of the host feeding preferences ofSitona weevils found commonly on white clover (Trifolium repens) in the UK

A series of laboratory and field studies were done to evaluate a range of leguminous plant species for their feeding potential by adult weevils of the genusSitona Germar. (Coleoptera: Curculionidae). Three species ofSitona, S. lineatus L.,S. flavescens Marsh. andS. hispidulus F. all of which are found commonly on white clover (Trifolium repens L.) in the UK were offered a range of 11 legume species,T. repens (white clover, cv. Olwen),T. pratense L. (red clover, cv. Marcom),T. fragiferum L. (strawberry clover, cv. Palestine),T. hybridum L. (hybrid clover, cv. Tetra),T. incarnatum L (crimson clover),T. dubium Sibth. (lesser yellow trefoil),Lotus corniculatus L. (birdsfoot-trefoil, cv. Leo),L. uliginosus Schkuhr. (large birdsfoot-trefoil),Melilotus alba Desr. (white melilot),Medicago sativa L. (lucerne, cv. Europe) andM. lupulina L. (black medick) in two laboratory experiments. The weevils were offered a choice of these legumes in one experiment whilst in the other they did not have a choice of food material. These legumes were also sown in the field and a number of measurements of damage, together with counts ofSitona spp., were made. In the laboratoryS. lineatus andS. hispidulus favoured some of the legumes to a greater or lesser extent than white clover.S. flavescens was more restricted in its feeding than the other two weevil species. In the field studyS. lineatus invaded the experimental area quickly and tended to favourMedicago spp. andMelilotus spp. Later in the yearS. flavescens dominated the sitona fauna on the experiment, with the exception of aggregations ofS. lineatus onM. sativa andM. alba. In a separate screen of 5 varieties of white clover (cvs Donna, Menna, Kersey, Olwen and Grasslands Huia), cv. Olwen appeared to be the most susceptible to sitona attack.     

Comparison of homoeolocus organisation in paired BAC clones from white clover (<Emphasis Type="Italic">Trifolium repens</Emphasis> L.) and microcolinearity with model legume species

Background  

White clover (Trifolium repens L.) is an outbreeding allotetraploid species and an important forage legume in temperate grassland agriculture. Comparison of sub-genome architecture and study of nucleotide sequence diversity within allopolyploids provides insight into evolutionary divergence mechanisms, and is also necessary for the development of whole-genome sequencing strategies. This study aimed to evaluate the degree of divergence between the O and P' sub-genomes of white clover through sequencing of BAC clones containing paired homoeoloci. The microsyntenic relationships between the genomes of white clover and the model legumes Lotus japonicus and Medicago truncatula as well as Arabidopsis thaliana were also characterised.     

Nitrogen fixation in perennial forage legumes in the field

Nitrogen acquisition is one of the most important factors for plant production, and N contribution from biological N₂ fixation can reduce the need for industrial N fertilizers. Perennial forages are widespread in temperate and boreal areas, where much of the agriculture is based on livestock production. Due to the symbiosis with N₂-fixing rhizobia, perennial forage legumes have great potential to increase sustainability in such grassland farming systems. The present work is a summary of a large number of studies investigating N₂ fixation in three perennial forage legumes primarily relating to ungrazed northern temperate/boreal areas. Reported rates of N₂ fixation in above-ground plant tissues were in the range of up to 373 kg N ha^–1 year^–1 in red clover (Trifolium pratense L.), 545 kg N ha^–1 year^–1 in white clover (T. repens L.) and 350 kg N ha^–1 year^–1 in alfalfa (Medicago sativa L.). When grown in mixtures with grasses, these species took a large fraction of their nitrogen from N₂ fixation (average around 80%), regardless of management, dry matter yield and location. There was a large variation in N₂ fixation data and part of this variation was ascribed to differences in plant production between years. Studies with experiments at more than one site showed that also geographic location was an important source of variation. On the other hand, when all data were plotted against latitude, there was no simple correlation. Climatic conditions seem therefore to give as high N₂ fixation per ha and year in northern areas (around 60°N) as in areas with a milder climate (around 40°N). Analyzing whole plants or just above-ground plant parts influenced the estimate of N₂ fixation, and most reported values were underestimated since roots were not included. Despite large differences in environmental conditions, such as N fertilization and geographic location, N₂ fixation (Nfix; kg N per ha and year) was significantly (P<0.001) correlated to legume dry matter yield (DM; kg per ha and year). Very rough, but nevertheless valuable estimations of Nfix in legume/grass mixtures (roots not considered) are given by Nfix = 0.026DM + 7 for T. pratense, Nfix = 0.031DM + 24 for T. repens, and Nfix = 0.021DM + 17 for M. sativa.     

Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland

Legumes play a crucial role in nitrogen supply to grass-legume mixtures for ruminant fodder. To quantify N transfer from legumes to neighbouring plants in multi-species grasslands we established a grass-legume-herb mixture on a loamy-sandy site in Denmark. White clover (Trifolium repens L.), red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.) were leaf-labelled with ¹⁵N enriched urea during one growing season. N transfer to grasses (Lolium perenne L. and xfestulolium), white clover, red clover, lucerne, birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), salad burnet (Sanguisorba minor L.) and caraway (Carum carvi L.) was assessed. Neighbouring plants contained greater amounts of N derived from white clover (4.8?g?m^-2) compared with red clover (2.2?g?m^-2) and lucerne (1.1?g?m^-2). Grasses having fibrous roots received greater amounts of N from legumes than dicotyledonous plants which generally have taproots. Slurry application mainly increased N transfer from legumes to grasses. During the growing season the three legumes transferred approximately 40?kg?N ha^-1 to neighbouring plants. Below-ground N transfer from legumes to neighbouring plants differed among nitrogen donors and nitrogen receivers and may depend on root characteristics and regrowth strategies of plant species in the multi-species grassland.     

Nitrogen accumulation in kaolin mining wastes in Cornwall III. Nitrogenous fertilisers

Summary In the establishment of a grass cover on china clay waste it is necessary, as in most land restoration, to supply fertiliser nitrogen in substantial amounts. However the objective of nitrogen accumulation is restricted in south west England by severe leaching. A series of experiments were devised to investigate the nitrogen retention from a range of fertiliser sources.When fertiliser-N was applied to established swards, three times as much nitrogen (about 90 per soil and vegetation at the end of the first season of establishment. Sodium nitrate was especially susceptible to leaching, in contrast to sources containing ammonium. Slow-release formulations and organic materials produced a lower sward growth throughout the first growing season but tended to give higher levels of residual-N in the sand waste.When fertiliser-N was applied at seeding less than 30 per cent of the nitrogen was retained in the cent of that applied) was retained. Most of this nitrogen was retained in the sand waste. There was little difference between different types of fertiliser: the main effect was to alter the amount of nitrogen in herbage tissues.Plant growth and a healthy grass sward could only be sustained in the absence of a legume component by repeated applications of fertiliser-N. When applications were discontinued sward degradation was shown by decreases in biomass. Losses in nitrogen from the sward biomass were more than accounted for by an increase in the nitrogen content of the sand waste. These results indicate that once fertiliser-N is retained by the sward ecosystem on sand waste, there are few further losses, presumably because of rapid microbial immobilisation of nitrogen in the sand waste.In view of the expense of land restoration using numerous maintenance applications of nitrogen, it is clear that legumes must be included in the seeds mixture for the reclamation of kaolin mining wastes in Cornwall. However, legumes are difficult to establish and more susceptible to drought than grass species. Results from these trials suggest that slow-release nitrogen fertilisers could enable a controlled level of grass growth, thereby avoiding competition between the legume and grass components. Alternatively grass swards could be rapidly established to stabilise the sand waste using soluble ammonium salts, and in the second season oversown with legumes.     

Characterization of novel microsatellite loci for red clover (Trifolium pratense L.) from enriched genomic libraries

Twenty‐seven polymorphic microsatellite markers were isolated from red clover (Trifolium pratense). Allelic variability and cross‐species amplification were assessed on 24 red clover and eight white clover (Trifolium repens) genotypes. The number of alleles detected in red clover ranged from two to 25. Observed and expected heterozygosities were high with average values of 0.71 and 0.88, respectively. Five of the 27 loci were also successfully amplified from white clover, where two to 13 alleles were detected. These highly polymorphic microsatellite loci provide powerful tools for population genetic studies as well as for marker‐assisted selection in this important forage legume species.     

The role of legumes as a component of biodiversity in a cross-European study of grassland biomass nitrogen

To investigate how plant diversity loss affects nitrogen accumulation in above‐ground plant biomass and how consistent patterns are across sites of different climatic and soil conditions, we varied the number of plant species and functional groups (grasses, herbs and legumes) in experimental grassland communities across seven European experimental sites (Switzerland, Germany, Ireland, United Kingdom (Silwood Park), Portugal, Sweden and Greece). Nitrogen pools were significantly affected by both plant diversity and community composition. Two years after sowing, nitrogen pools in Germany and Switzerland strongly increased in the presence of legumes. Legume effects on nitrogen pools were less pronounced at the Swedish, Irish and Portuguese site. In Greece and UK there were no legume effects. Nitrogen concentration in total above‐ground biomass was quite invariable at 1.66±0.03% across all sites and diversity treatments. Thus, the presence of legumes had a positive effect on nitrogen pools by significantly increasing above‐ground biomass, i.e. by increases in vegetation quantity rather than quality. At the German site with the strongest legume effect on nitrogen pools and biomass, nitrogen that was fixed symbiotically by legumes was transferred to the other plant functional groups (grasses and herbs) but varied depending on the particular legume species fixing N and the non‐legume species taking it up. Nitrogen‐fixation by legumes therefore appeared to be one of the major functional traits of species that influenced nitrogen accumulation and biomass production, although effects varied among sites and legume species. This study demonstrates that the consequences of species loss on the nitrogen budget of plant communities may be more severe if legume species are lost. However, our data indicate that legume species differ in their N₂ fixation. Therefore, loss of an efficient N₂‐fixer (Trifolium in our study) may have a greater influence on the ecosystem function than loss of a less efficient species (Lotus in our study). Furthermore, there is indication that P availability in the soil facilitates the legume effect on biomass production and biomass nitrogen accumulation.     

Performance of the legume-feeding herbivore, Colias philodice (Lepidoptera: Pieridae) is not Affected by Elevated CO2

Presumably due to their association with nitrogen-fixing bacteria, the nutritional quality of legumes decreases less than that of non-legume C₃ plants when grown under elevated atmospheric CO₂. Therefore, it seems likely that legume-feeding herbivores will be less adversely affected than herbivores of non-legume C₃ plants by anthropogenic increases in atmospheric CO₂. When the legumes Medicago sativa (alfalfa), Trifolium repens (white clover), and Lotus corniculatus (birdsfoot trefoil) were grown under elevated (756 ppm) CO₂, leaf nitrogen remained the same or increased, and C:N ratio did not change. Unlike most insects fed non-legume C₃ plants, Colias philodice (sulfur butterfly) larvae fed elevated-grown M. sativa and T. repens did not exhibit reduced relative growth rate (RGR), and larvae fed elevated-grown L. corniculatus exhibited a nearly significant 37% increase in RGR. Pupal weight was unaffected by growth of host plants under elevated CO₂. Relative nitrogen growth rate (RGRN) did not change for larvae fed elevated-grown M. sativa or T. repens, but increased by 34% for larvae fed elevated-grown L. corniculatus. These results suggest that legume-feeding herbivores will be relatively buffered against the adverse effects of elevated CO₂ typically experienced by herbivores of non-legume C₃ plants.     

Nitrogen fertilization effects on dinitrogen fixation as influenced by legume species and proportion in legume-grass mixtures in Uruguay

Grasses grown in mixture with nodulated legumes often are N-limited, but N fertilization may result in reductions of N₂ fixation and legume stands. We studied N-fertilizer effects on N₂ fixation for three binary legume-grass mixtures in Uruguay. Replicated swards of white clover (Trifolium repens L.) (WC), red clover (Trifolium pratense L.) (RC), or birdsfoot trefoil (Lotus corniculatus L.) (BT), each in combination with tall fescue (Festuca arundinacea Schreb) (TF) at two legume proportions were sown in 1983 (Exp. 1) and 1984 (Exp. 2). In the fall of 1984, N treatments at 100 kg ha⁻¹ and controls were randomly assigned to subplots in Exp. 1 (established swards) and in Exp. 2 (at seeding). The soil for both experiments was a fine, montmorillonitic, mesic, Typic Argiudolls. Herbage fixed-N was estimated by ¹⁵N isotope-dilution with pure stands of TF as reference. In both experiments, N fertilization reduced the proportion of legume N derived from air (% Ndfa) and increased herbage yield only during the first 18 to 20 weeks after application. Fertilizer-N reduced annual fixed-N yield from 178 to 148 kg ha⁻¹ in Exp. 1 and from 65 to 29 kg ha⁻¹ in Exp. 2 Fixed-N yield for BT was markedly reduced by N in both experiments (33 to 53%), whereas for the clovers reduction was lesser in Exp. 1 (9 to 13%) than in Exp. 2 (46 to 64%). Negative effects of N on % Ndfa were more evident for the high legume proportion. We conclude that fertilization with 100 kg N ha⁻¹ reduced % Ndfa only for the immediate 18 to 20 weeks after application. Fertilizer-induced reduction of fixed-N yields lasted longer because of a more prolonged depression of legume proportion, especially for BT and for newly seeded swards. Journal Paper no. J.-13327 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, U.S.A. (Project 2281). Supported in part by the Facultad de Agronomía, Montevideo, Uruguay; and the International Atomic Energy Agency, Vienna, Austria (Project URU/5/012). Journal Paper no. J.-13327 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, U.S.A. (Project 2281). Supported in part by the Facultad de Agronomía, Montevideo, Uruguay; and the International Atomic Energy Agency, Vienna, Austria (Project URU/5/012).     

Stability of CaMV 35S-gus gene expression in (bird's foot trefoil) hairy root cultures under different growth conditions

Lotus corniculatus is an agronomically important forage legume. Genetic engineering offers opportunities both to improveL. corniculatus as a crop and to increase basic understanding of plant biochemistry and metabolism. Biosynthesis of secondary products and nitrogen fixation are two areas in which gene expression has been studied using hairy root cultures ofL. corniculatus. The stability of foreign gene expression in these cultures is critically important. TwoL. corniculatus root culture lines containing a reporter gene (CaMV 35S-gus) were used to investigate the stability of expression of a foreign gene under a range of conditions likely to be encountered in experiments. The hairy root culture lines were grown under varying conditions of light, temperature, nutrient supply, and in the presence of the auxin 2,4-D, or the elicitor glutathione. Expression of thegus gene, detected by measuring GUS activity, was found to be relatively stable under all of the conditions investigated.     

Nitrogen accumulation in kaolin mining wastes in cornwall I. Natural communities

Summary Plant succession was investigated on sand waste heaps produced by kaolin mining in central Cornwall. It was found that relatively even aged, monospecific stands of vegetation were frequently present. The principal colonists were woody leguminous plants which, in some situations, were superceded by a massive growth of rhododendrons (Rhododendron ponticum) or native woodland species. Where legumes were absent, the waste was slowly colonised by Calluna vulgaris and other heathland species.The age structure of the vegetation was negatively and significantly correlated (r=–0.71) with the moisture deficit (evapotranspiration minus rainfall) during the spring and early summer. Drought, limited seed availability, and low nitrogen levels in the waste material are factors which contribute to the development of monospecific, even-aged legume communities of Ulex europaeus, Sarothamnus scoparius and Lupinus arboreus.Measurements were made of biomass and litter in five plant communities and nitrogen levels were determined in the soil/plant system within these communities and also in the soil of a woodland which had developed on sand waste. The low productivity and low rate of nitrogen accumulation in a stand of Calluna vulgaris contrasted with stands of the three woody legumes. Gorse (Ulex europaeus) accumulated nitrogen most rapidly and appeared to have preceded invasion by Rhododendron ponticum and transition to native woodland. Within the woodland and rhododendron thicket the soil nitrogen levels approached those characteristic of temperate climax woodland.The data indicate that the course of plant succession and the rate of soil development are strongly influenced by the biological properties of the colonising species. These processes are accelerated considerably following the invasion of woody legumes. re]19760512Department of Botany Liverpool University     

Germination and Initial Root Growth of Four Legumes as Affected by Landfill Biogas Atmosphere

The most important problem in the restoration of closed landfills is the production of toxic gases by decomposition of refuse. Such gases affect the root system of plants growing on these sites. The aim of the present study was to assess the effects induced by landfill biogas contamination on germination and initial root growth of Vicia villosa (hairy vetch), Lotus corniculatus (birdsfoot trefoil), Trifolium pratense (red clover), and Trifolium repens (white clover). In laboratory conditions, simulated landfill and control gas were supplied to the seedlings. The composition of the simulated landfill gas used was: 16% O₂, 8% CO₂, 3% CH₄, and 73% N₂; a control gas was also tested (21% O₂, 0. 035% CO₂, and 78% N₂). Percentage of germinated seeds was determined after 6 and 12 days from the starting date; at the same time qualitative assays of metabolic root functionality were also performed by using an agar technique in order to visualize changes in rhizosphere pH. At the end of the experiment, the length of the primary and secondary root was measured. Germination after 6 days was affected by the gas treatment; the landfill biogas caused a delay in germination with respect to the control in seeds of V. villosa and L. corniculatus. Root fresh weight and dry weight were significantly decreased by biogas treatment in V. villosa and T. repens. In contrast, root dry weight was higher in gas treated L. corniculatus and T. pratense compared to control seedlings. Total root system was significantly higher in treated T. pratense. The qualitative assay suggests, with the exception of T. pratense, a metabolic adjustment of the treated seedlings. Key words: restoration, landfill biogas, legumes.     

Linkage between root systems of three pioneer plant species and soil nitrogen during early reclamation of a mine site in Lusatia,Germany

In 2005, a 7‐ha artificial watershed (Chicken Creek) was built on a post mined landscape in Lusatia, Germany from sandy substrates of Pleistocene origin, commonly used in reclamation. The watershed was developed to investigate the initial phase of soil and ecosystem development under natural conditions. At this early stage, mineral nitrogen in young sandy soils is primarily limited and nitrogen fixing legumes become key components of natural succession. Local abundant pioneering legumes Lotus corniculatus and Trifolium arvense and one pioneer grass species Calamagrostis epigeios were investigated 5 years after watershed construction. In this study, we investigated the influence of spatial root and nodule distribution of these species on soil nitrogen accumulation. Soil, including roots, was sampled from field monoliths covered with the aforementioned plant species. Root systems of both legumes were mainly restricted to the upper 20 cm of soil, whereas roots of C. epigeios also developed strongly at greater depths. A positive relationship was found, with higher plant densities associated with higher root densities which were associated with higher nodule densities for legumes and which were all associated with significantly higher soil nitrogen content relative to non‐vegetated areas. This research provides rare information on the role root systems of pioneer legumes play in soil nitrogen input in the early stage of soil and ecosystem development during revegetation by natural succession.     

Transformation of forage legumes using Agrobacterium tumefaciens

Summary Galls were induced in six species of forage legumes following inoculation with wild-type strains of A. tumefaciens. The plant species was more influential than the bacterial strain in determining the type of tumour produced. Inoculation of Medicago sativa resulted in small, disorganised tumours. The three Trifolium species, T. repens, T. hybridum and T. pratense, formed galls which tended to produce roots and both Onobrychis viciifolia and Lotus corniculatus produced teratomatous galls. The shoots elongated in the latter species only. In L. corniculatus, tissues that were infected by five bacterial strains were capable of shoot regeneration when cultured on a hormone-free medium. The transformed nature of these shoots was confirmed by their failure to root, the production of callus from leaves cultured on hormone-free medium and the presence of opines.     

The response of certainTrifolium spp. to calcium in sand culture

Summary The response to calcium ofTrifolium incarnatum, T. pratense, T. repens andT. hybridum was determined over the range 4 to 128 ppm calcium in sand culture.T. incarnatum showed the greatest response to calcium and was severely affected by low levels of calcium.T. hybridum was the least responsive to calcium and showed no significant response over the range tested, although a gradual increase in yield with increasing calcium was apparent. The responses ofT. pratense andT. repens were intermediate and differed significantly from those of bothT. incarnatum andT. hybridum. There was no significant difference between the response ofT. pratense andT. repens.The results are considered in the light of the ecologically observed edaphic tolerances of the species, and it is concluded that there is a marked relationship between response to calcium and edaphic tolerance of the species.In view of the differences in response to calcium recently demonstrated within the speciesT. repens, the magnitude of the differences between species shown here may not strictly apply to all varieties or populations of those species.     

Control of Legumes in a Species-Rich Meadow Re-created on Land Restored after Opencast Coal Mining

Aggressive growth by legumes may restrict the diversity of species-rich meadows recreated on sites restored after mineral extraction. We investigated the ability of mineral nitrogen (N) applications and spring grazing to control the legume component of such meadows. The use of N suppressed Trifolium repens but had no effect on other legume species or on the species richness, diversity, or equitability of the meadow community. Spring grazing significantly reduced the yield from the legume component of the meadow. This was accompanied by an increase in the equitability index of the community, suggesting that the aggressive nature of the legumes had been checked. Spring grazing may therefore provide a means of controlling aggressive legume growth and may maintain the diversity of species-rich meadows established on restored sites.