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• The legume genus Mimosa has > 500 species, with two major centres of diversity, Brazil (c. 350 spp.) and Mexico (c. 100 spp.). In Brazil most species are nodulated by Burkholderia. Here we asked whether this is also true of native and endemic Mexican species. • We have tested this apparent affinity for betaproteobacteria by examining the symbionts of native and endemic species of Mimosa in Mexico, especially from the central highlands where Mimosa spp. have diversified. Nodules were tested for betaproteobacteria using in situ immunolocalization. Rhizobia isolated from the nodules were genetically characterized and tested for their ability to nodulate Mimosa spp. • Immunological analysis of 25 host taxa suggested that most (including all the highland endemics) were not nodulated by betaproteobacteria. Phylogenetic analyses of 16S rRNA, recA, nodA, nodC and nifH genes from 87 strains isolated from 20 taxa confirmed that the endemic Mexican Mimosa species favoured alphaproteobacteria in the genera Rhizobium and Ensifer: this was confirmed by nodulation tests. • Host phylogeny, geographic isolation and coevolution with symbionts derived from very different soils have potentially contributed to the striking difference in the choice of symbiotic partners by Mexican and Brazilian Mimosa species. [ABSTRACT FROM AUTHOR]

•An extensive survey of nodulation in the legume genus Mimosa was undertaken in two major biomes in Brazil, the Cerrado and the Caatinga, in both of which there are high degrees of endemicity of the genus. •Nodules were collected from 67 of the 70 Mimosa spp. found. Thirteen of the species were newly reported as nodulating. Nodules were examined by light and electron microscopy, and all except for M. gatesiae had a structure typical of effective Mimosa nodules. The endosymbiotic bacteria in nodules from all of the Mimosa spp. were identified as Burkholderia via immunolabelling with an antibody against Burkholderia phymatum STM815. •Twenty of the 23 Mimosa nodules tested were shown to contain nitrogenase by immunolabelling with an antibody to the nitrogenase Fe- ( nifH) protein, and using the δ15N (15N natural abundance) technique, contributions by biological N2 fixation of up to 60% of total plant N were calculated for Caatinga Mimosa spp. •It is concluded that nodulation in Mimosa is a generic character, and that the preferred symbionts of Brazilian species are Burkholderia. This is the first study to demonstrate N2 fixation by beta-rhizobial symbioses in the field. [ABSTRACT FROM AUTHOR]

• The ability of Burkholderia phymatum STM815 to effectively nodulate Mimosa spp., and to fix nitrogen ex planta, was compared with that of the known Mimosa symbiont Cupriavidus taiwanensis LMG19424. • Both strains were equally effective symbionts of M. pudica, but nodules formed by STM815 had greater nitrogenase activity. STM815 was shown to have a broader host range across the genus Mimosa than LMG19424, nodulating 30 out of 31 species, 21 of these effectively. LMG19424 effectively nodulated only nine species. GFP-marked variants were used to visualise symbiont presence within nodules. • STM815 gave significant acetylene reduction assay (ARA) activity in semisolid JMV medium ex planta, but no ARA activity was detected with LMG19424. 16S rDNA sequences of two isolates originally from Mimosa nodules in Papua New Guinea (NGR114 and NGR195A) identified them as Burkholderia phymatum also, with nodA, nodC and nifH genes of NGR195A identical to those of STM815. • B. phymatum is therefore an effective Mimosa symbiont with a broad host range, and is the first reported beta-rhizobial strain to fix nitrogen in free-living culture. [ABSTRACT FROM AUTHOR]

Focuses on a study which described the photosynthetic response of Mimosa pudica. Materials and methodology; Link between electrical signaling and photosynthetic response of plants; Mechanisms involved in electrical signal transmission in plants.

The mechanism of wound signalling in Mimosa is discussed with a brief historical survey. It is demonstrated that strong wound-induced hydraulic signals occur in Mimosa pudica L., as in many other plants, and that the basipetal mass flows associated with these events could disperse solutes from the wound site at rates of at least 15mm s-1, and possibly up to 300mm -1. When such wound-induced 'hydraulic dispersal' is taken into account, Ricca's theory of chemical signalling can explain long-distance transmission in Mimosa. The pattern of long-distance wound signalling in Mimosa is shown to be consistent with such a model. Implications for theories of electrical signalling in Mimosa are discussed and it is concluded, in agreement with some previous workers, that systemic wound-induced electrical phenomena in Mimosa art not travelling signals, but are local responses to the travelling chemical messengers. [ABSTRACT FROM AUTHOR]

In order to investigate population variation and its maintenance in groundsel (Senecio vulgaris L.) growing in the Cambridge University Botanic Garden, experiments have been carried out to study heritable differences in the rate of development of progenies of seed-parents from sites of different history and land use in and round the Garden. There were significant differences between progenies of seed-parents and between samples from different flowerheds but the oldest beds did not have the quickest developing plants. Such a pattern of behaviour may be related to the fact that all the beds have been well maintained since the 1950s. Since its establishment, two distinctive genetic variants have entered the Garden. On average, progenies from radiate and from simazine-resistant seed-parents in the study area were significantly slower to develop than non- radiate simazine-sensitive plants hut, in both cases, we also found plants of intermediate rate of development, which might be the result of hybridization between the `immigrants' and the precociously developing non-radiate, herbicide-sensitive plants. Progenies from seed-parents collected at two sites just outside the boundaries of the Botanic Garden were slower in their rate of development than those from the intensively hand-weeded flowerbeds of the Garden. Samples collected from the same area in different seasons, and grown at the same time, did not differ overall in rate of development, hut there were significant differences within flowerbeds. Subsets of progenies of a set of seed-parents were grown both in summer and winter. The rank order of maturity was not the same in the two parts of the experiment, indicating that the progeny of different seed-parents have different relative fitness in different times of year. This behaviour, in a species which is capable of reproducing at all seasons of the year, could be a major factor in the maintenance of population variation in the Garden proper. [ABSTRACT FROM AUTHOR]

Parasponia andersonii was nodulated by thirty four of thirty nine slow-growing rhizobia isolated from tropical legumes and by R. japonicum and R. lupini. The nitrogenase activity of nodulated plants within a rhizobial treatment varied widely. Effective associations were obtained with some but not all isolates from Cajanus cajan, Centrosema pubescens, Crotalaria anagyroides, Flemingia congesta, Inocarpus fragiferum, Macroptilium lathyroides, Phaseolus calcaratus, Stizolobium deeringianum and Stylosanthes gracilis. Little or no nitrogen was fixed with rhizobia from Albizia stipulata, Cassia mimosoides, Desmodium microphyllum, Pterocarpus indicus, Uraria lagopoides, and the wide-host range cowpea Rhizobium strain CB 756. Fast-growing rhizobia from Leucaena leucocephala, Mimosa invisa, M. pudica, Sesbania grandiflora and Lablab purpureus nodulated Parasponia with a low level of nitrogen fixation. Isolates from Parasponia failed to nodulate most of the legumes usually nodulated by slow- growing rhizobia and when tropical legumes were nodulated, the association was either partially effective or ineffective; only isolate CP 283 was highly effective and promiscuous. Hosts normally nodulated with fast-growing rhizobia, including Leucaena and Mimosa were not nodulated with isolates from Parasponia. It was concluded that the Parasponia-Rhizobium symbiosis is best located in the 'cowpea miscellany'. [ABSTRACT FROM AUTHOR]

Following mechanical stimulation, the leaves of Mimosa close and their photosynthetic rate declines by 40%. The translocation rate remains constant during leaf closure suggesting that blockage of transport by rapid sieve plate callose formation is not occurring. The rates of photosynthesis and translocation do not appear to be closely coupled. [ABSTRACT FROM AUTHOR]