O. N. Allen

Bio: O. N. Allen is an academic researcher from University of Hawaii. The author has contributed to research in topics: Tribe (biology) & Root nodule. The author has an hindex of 11, co-authored 13 publications receiving 963 citations.

The Leguminosae: A Source Book of Characteristics, Uses and Nodulation

Abstract: This encyclopedic global survey of leguminous root nodulation, the result of 45 years of research by O. N. Allen and Ethel K. Allen, is the only one of its kind, a massive effort incorporating all of the 750 known genera of" Leguminosae," which, in turn, include nearly 20,000 species. The volume contains a comprehensive taxonomic account of the family "Leguminosae" as a framework for the author s census report of the nodulating and non-nodulating genera and species. The main body of the work consists of synopses of 750 leguminous genera arranged alphabetically. Each is described taxonomically within its proper tribe and subfamily, in accordance with accepted classification systems. All of the nodulation data from the survey are further summarized in tabular alphabetical listings of genera under each of the three subfamily categories. Throughout the volume there are previously unpublished personal observations, both those of the authors and of the many scientists whom they have contacted and worked with during their more than four decades of research."

Response of the peanut plant to inoculation with rhizobia, with special reference to morphological development of the nodules.

Abstract: 1. Each of fifty-nine strains of rhizobia, isolated from a variety of leguminous plants, proved infective upon the roots of the peanut plant. Seventeen strains markedly enhanced plant growth and nine were effective to a less extent, in contrast to thirty-three strains which were decidedly non-beneficial. 2. All nodules, irrespective of size and the sources of inocula, were located in root axils. Those produced by the non-beneficial strains were inconspicuous and tended to be visible only when the roots were immersed in water. 3. Abnormal nodose formations, which proved to be merely hypertrophied parenchymatous tissue containing heavy deposits of starch, were frequently found at the base of the rootlets of plants deficient in nitrogen. 4. Infection of roots results from invasion of rhizobia through the ruptured tissue at the site of lateral root emergence. Lateral or normal root hair formation is rare, whereas tufted whorled rosettes of hairs are common in the root axils. No data were obtained supporting r...

Biological aspects of symbiotic nitrogen fixation

Abstract: The subject of symbiosis between the root nodule bacteria and leguminous plants, as reflected in the practical significance of nitrogen fixation, has had a broad and comprehensive development. Two authoritative volumes (Fred, Baldwin and McCoy 1932, Wilson 1940) are well known. Less extensive reviews in recent years have concerned specialized topics (Allen and Allen 1950, 1954, Allen and Baldwin 1955, Thornton 1954, Vincent 1954a, Virtanen 1947, Wilson and Burris 1947).

Plant invasions--the role of mutualisms.

Abstract: Many introduced plant species rely on mutualisms in their new habitats to overcome barriers to establishment and to become naturalized and, in some cases, invasive. Mutualisms involving animal-mediated pollination and seed dispersal, and symbioses between plant roots and microbiota often facilitate invasions. The spread of many alien plants, particularly woody ones, depends on pollinator mutualisms. Most alien plants are well served by generalist pollinators (insects and birds), and pollinator limitation does not appear to be a major barrier for the spread of introduced plants (special conditions relating to Ficus and orchids are described). Seeds of many of the most notorious plant invaders are dispersed by animals, mainly birds and mammals. Our review supports the view that tightly coevolved, plant-vertebrate seed dispersal systems are extremely rare. Vertebrate-dispersed plants are generally not limited reproductively by the lack of dispersers. Most mycorrhizal plants form associations with arbuscular mycorrhizal fungi which, because of their low specificity, do not seem to play a major role in facilitating or hindering plant invasions (except possibly on remote islands such as the Galapagos which are poor in arbuscular mycorrhizal fungi). The lack of symbionts has, however, been a major barrier for many ectomycorrhizal plants, notably for Pinus spp. in parts of the southern hemisphere. The roles of nitrogen-fixing associations between legumes and rhizobia and between actinorhizal plants and Frankia spp. in promoting or hindering invasions have been virtually ignored in the invasions literature. Symbionts required to induce nitrogen fixation in many plants are extremely widespread, but intentional introductions of symbionts have altered the invasibility of many, if not most, systems. Some of the world's worst invasive alien species only invaded after the introduction of symbionts. Mutualisms in the new environment sometimes re-unite the same species that form partnerships in the native range of the plant. Very often, however, different species are involved, emphasizing the diffuse nature of many (most) mutualisms. Mutualisms in new habitats usually duplicate functions or strategies that exist in the natural range of the plant. Occasionally, mutualisms forge totally novel combinations, with profound implications for the behaviour of the introduced plant in the new environment (examples are seed dispersal mutualisms involving wind-dispersed pines and cockatoos in Australia; and mycorrhizal associations involving plant roots and fungi). Many ecosystems are becoming more susceptible to invasion by introduced plants because: (a) they contain an increasing array of potential mutualistic partners (e.g. generalist frugivores and pollinators, mycorrhizal fungi with wide host ranges, rhizobia strains with infectivity across genera); and (b) conditions conductive for the establishment of various alien/alien synergisms are becoming more abundant. Incorporating perspectives on mutualisms in screening protocols will improve (but not perfect) our ability to predict whether a given plant species could invade a particular habitat.

Towards an ecological understanding of biological nitrogen fixation

Abstract: N limitation to primary production and other ecosystem processes is widespread. To understand the causes and distribution of N limitation, we must understand the controls of biological N fixation. The physiology of this process is reasonably well characterized, but our understanding of ecological controls is sparse, except in a few cultivated ecosystems. We review information on the ecological controls of N fixation in free-living cyanobacteria, vascular plant symbioses, and heterotrophic bacteria, with a view toward developing improved conceptual and simulation models of ecological controls of biological N fixation.

Soil biota and invasive plants

Abstract: Interactions between plants and soil biota resist invasion by some nonnative plants and facilitate others. In this review, we organize research and ideas about the role of soil biota as drivers of invasion by nonnative plants and how soil biota may fit into hypotheses proposed for invasive success. For example, some invasive species benefit from being introduced into regions of the world where they encounter fewer soil-borne enemies than in their native ranges. Other invasives encounter novel but strong soil mutualists which enhance their invasive success. Leaving below-ground natural enemies behind or encountering strong mutualists can enhance invasions, but indigenous enemies in soils or the absence of key soil mutualists can help native communities resist invasions. Furthermore, inhibitory and beneficial effects of soil biota on plants can accelerate or decelerate over time depending on the net effect of accumulating pathogenic and mutualistic soil organisms. These 'feedback' relationships may alter plant-soil biota interactions in ways that may facilitate invasion and inhibit re-establishment by native species. Although soil biota affect nonnative plant invasions in many different ways, research on the topic is broadening our understanding of why invasive plants can be so astoundingly successful and expanding our perspectives on the drivers of natural community organization.

Developmental biology of legume nodulation

Abstract: SUMMARY Many legumes respond to Rhizobium inoculation by developing unique structures known as nodules on their roots. The development of a legume nodule in which rhizobia convert atmospheric N2 into ammonia is a finely tuned process. Gene expression from both partners of the symbiosis must be temporally and spatially coordinated. Exactly how this coordination takes place is an area of intense study. Nodule morphogenesis appears to be elicited by at least two distinct signals: one from Rhizobium, a product of the nod genes (Nod factor), and a second signal, which is generated within plant tissues after treatment with Nod factor. The identity of the second signal is unknown but changes in the balance of endogenous plant hormones or the sensitivity of plant tissues to these hormones are likely to be involved. These hormonal changes may be triggered by endogenous flavonoids produced by the root in response to inoculation with Rhizobium. There is some controversy as to whether the legume nodule is an organ sui generis or a highly derived lateral root. A resolution of this question may become more critical as attempts to induce nodules on non-legume hosts, such as rice or maize, increase in number and scope.

Lotus japonicus, an autogamous, diploid legume species for classical and molecular genetics

Abstract: Summary In the Leguminosae plant family, few of the individual plant species have been used for plant molecular biology research. Among the species investigated no obvious representative ‘model’ legume has emerged. Here a member of the tribe Loteae, Lotus japonicus (Regel) Larsen is proposed as a candidate. L. japonicus is a diploid, autogamous species, with a good seed set, and a generation time of approximately 3 months. The haploid genome consists of six chromosomes and the genome size was estimated to be relatively small (0.5 pg per haploid complement). L. japonicus is susceptible to Agrobacterium tumefaciens and transgenic plants can be regenerated after hygromycin or kanamycin selection. Tissue culture conditions and procedures for transformation and regeneration are described. Stable transformation is demonstrated by segregation of the hygromycin selectable marker after selfing of transgenic plants or test crosses. The possibility of mapping polymorphic DNA markers inbred lines of L. japonicus is also discussed.