Daphne J. Osborne (1925–2006)
E-mail: irene_ridge{at}btinternet.com
E-mail: mike.jackson{at}bristol.ac.uk
There has been a plethora of tributes and obituaries for Daphne Osborne, who died in Oxford, UK on June 16th 2006 and in whose honour this Special Issue is produced. A collection of papers covering her areas of interest is probably the best tribute we can pay to someone who was an active researcher for over 50 years and one of the leading plant physiologists of her generation.
Daphne Osborne had a passionate interest in how plants grow and survive. She was an acute observer with a truly enquiring mind, so that chance observations often led to new projects, such as why do the juvenile leaves of oak and beech not fall off in autumn and how do the flower stems of daffodils (Narcissus) bend down at the tips before flowers open? What prevents certain seeds from germinating? What initiates the explosive dehiscence of Ecballium elaterium? Daphne was no dilettante, however, and she and her many research students and colleagues investigated a select group of topics in great detail, notably the role(s) of growth regulators (especially ethylene and auxin) in cell expansion, abscission, and senescence and seed viability. The outcome was over 200 research papers and countless invited lectures in numerous countries.
Daphne Osborne's research career began with a PhD from the University of London under the supervision of R. L. Wain at Wye College. Her thesis, published in 1950, was titled Studies on Plant Growth Regulators and she continued to work in this field for the rest of her life. A postdoctoral travelling fellowship was spent at the California Institute of Technology where, among others, she worked with the veteran botanist and pioneer of plant hormone research, Fritz Went. On her return to England, Daphne joined the Agricultural Research Council (ARC) Unit of Experimental Agronomy at the Department of Agricultural Science at Oxford University, where she remained until the Unit closed in 1970 after the retirement of its director, Professor G. E. Blackman. One of the Unit's main interests was selective herbicides and Daphne co-published several papers on the action of auxin herbicides during the 1950s. Her real interest, however, was in endogenous regulators: identifying what they were, what they did and how they worked.
In 1955, Daphne published a paper in Nature entitled ‘Acceleration of abscission by factors in senescent leaves’ (Osborne, 1955). After this, the topic of senescence (considered by Yang et al., 2008 in this Special Issue) and its link with abscission were to be key themes in Daphne's research for many years. Her first research student (Roger Horton) worked on abscission, as did others at later times. To track down the illusive abscission-promoting signal (dubbed ‘senescence factor’) from yellowing leaves, many kilograms of autumnal leaves were collected from the cherry trees outside the Physical Chemistry Laboratory at Oxford, but ‘senescence factor’ was never identified despite intense analysis by chromatography and mass spectrometry made in collaboration with Barry Milborrow, then working for Shell Research Ltd at their Milstead Laboratory at Sittingbourne in Kent. However, this study did at least help to question the hitherto presumed causal link between the hormone abscisic acid and the timing of leaf fall (Osborne et al., 1972) and encouraged a focus on ethylene as the prime instigator of abscission. Her fascination with abscission-promoting signals resurfaced some time later with an elegant demonstration of an essential abscission-promoting signal emanating from distal stele tissues (Thompson and Osborne, 1994). Daphne also became deeply interested in ethylene action in expanding cells (Ridge and Osborne, 1971), with a focus on cell walls. This theme is a particular feature of one of the papers included in this Special Issue (Thompson, 2008). Daphne's work thus did much to promote ethylene as a natural regulator rather than a pollutant or by-product of senescent tissue (a view that persisted among some plant physiologists into the 1970s). Interactions between ethylene and auxin remained a lifelong interest and auxin action is the theme of two of the papers included in this Special Issue (Abebie et al., 2008; Bar-Nun et al., 2008)
Whilst at Oxford, a combination of serendipity and good management helped Daphne to broaden her horizons and to embrace new techniques and research systems. A fruitful collaboration with Mary Hallaway led to work on protein and RNA synthesis (Osborne and Hallaway, 1964), which was further progressed by a sabbatical visit to Cal Tech, and by visitors such as Joe Cherry and David Chen and collaboration with Tristram Dyer. In turn, there followed much work on seeds, especially their viability in relation to DNA degradation and repair, that developed into her next lifelong interest and many fruitful collaborative projects. Several papers in this Special Issue are testament to this (Berjak and Pammenter, 2008; Huang et al., 2008; Qu et al., 2008). However, there were some notable digressions. Daphne was always interested in insects and in the mid-1960s she collaborated with the Anti-locust Research Centre at Wright's Lane, London to investigate the influence of plant growth regulators on locust development. Cages of locusts decorated her laboratory and it was shown that gibberellins in their food affected instar length (Ellis et al., 1965). By 1970, however, the Oxford Unit had closed and Daphne transferred to Cambridge, where she became Deputy Director of the new ARC Unit of Developmental Botany. Her research accelerated into the fast lane.
Whilst at Oxford, the possibilities of taking on research students were strictly limited and Daphne's first came only in 1964. At Cambridge there were far more research students and associates and excellent new facilities, including a range of gas chromatographs, fledgling molecular techniques for protein and nucleic acid analysis, and a fine electron microscope suite. This last, coupled with co-workers such a John Sargent, allowed Daphne to link physiology with fine structure and she made very good use of this opportunity (e.g. Sargent et al., 1981). There were also new experimental systems such as the nodes of grass stems in which, with Michael Wright (Osborne and Wright, 1978), she studied the role of gravity in cell elongation and developed a project for the European Space Agency's Spacelab programme. Daphne worked briefly on ethylene synthesis in cultivated mushrooms (Agaricus bisporus) and, following on from the work of Alan Musgrave and Mike Jackson, developed an interest in the ethylene-stimulated growth of semi-aquatic plants during submergence (Osborne, 1984a). A review of this topic is included in the present issue (Jackson, 2008). It was the interactions of ethylene and auxin in abscission zones, however, that contributed most to the development of the Osborne concept of ‘target cells’ – cells in particular positions that become sensitized to respond to endogenous regulators (Osborne, 1984b). With Michael McManus, she eventually published a book on this subject in the year before her death (Osborne and McManus, 2005) and the topic is taken further in the present Special Issue (McManus, 2008). Daphne certainly flourished at Cambridge and developed strong links with Churchill College, which was conveniently within walking distance of her laboratory. She became Churchill's first woman fellow and supervised the College's first female PhD student, Swati Sen (now Swati Sen-Mandi). Sadly, however, her time there was all too short. Following the retirement in 1977 of Professor P. W. Brian, a pioneer in gibberellin biochemistry and Director of the Unit, ARC tradition was followed and the Cambridge Unit eventually closed.
Daphne now moved back to Oxford, this time to the ARC Weed Research Organization (WRO) at Begbroke, just outside the city. She built up a flourishing research group all over again. Here began her association with Michael McManus, which led to a series of papers on target cells and, after a long gestation, the book mentioned above. There was work on dormancy in potato tubers and numerous papers on DNA repair, longevity and desiccation tolerance in seeds. Whilst at the WRO, Daphne was especially proud of her promotion to one of the most senior ranks in the British Scientific Civil Service, that of Deputy Chief Scientific Officer, but the WRO was closed down by ARC (by then AFRC) in 1985, which was also the year that Daphne was obliged to retire, having reached the normal Civil Service retirement age of 60 years.
For someone with Daphne's drive and energy, retirement in the usual sense was not an option. She became an Honorary Research Fellow of the Open University (working with Irene Ridge) and secured laboratory space in the Department of Plant Science at Oxford as well as renewing her links with Somerville College and becoming an Honorary Research Fellow there. The flow of reviews and research papers continued and, with Louise Stange, Daphne worked on another unusual system, the aquatic liverwort Riella helicophylla, where auxin and ethylene interact to induce faster cell expansion (‘supergrowth’; Stange and Osborne, 1988). There were also numerous visits to research laboratories in other countries, a tradition that Daphne kept up throughout her working life. She was an inveterate visitor and receiver of visitors and, whenever possible, made a special effort to visit developing countries, which included India, Malaysia, Nigeria and South Africa. Daphne had especially strong links to Israel, making several visits and establishing some warm and lasting friendships. Latterly, she had begun developing collaborations with scientists in China. Daphne was indeed a truly international scientist, known and respected in every continent. Further evidence, if that were needed, of Daphne's disregard for anything remotely suggesting retirement, and her enthusiastic engagement with science internationally was her organizing of a highly successful NATO Advanced Research Workshop in Turin, Italy in 1988 on cell separation processes in plants (Osborne and Jackson, 1989) attended by speakers from Japan, New Zealand, USA, the Caribbean, Europe, Israel and Iran.
From the early 1990s until her death, the final research home of Daphne Osborne was the Oxford Research Unit of the Open University, situated in the beautiful grounds of the Open University's Regional Centre for the South at Foxcombe Hall. Yet another research lab was organized and Daphne started a major new project with Janice Henderson on abscission in the fruits of oil palm (Elaeis guineensis), where it turned out that an unusual two-phase process determined the position and hence weakening of the abscission zone. In case you wondered how anyone in England could work on a tropical tree, Daphne received regular air shipments of material through her sponsors, Unilever. She published two popular science articles on oil palms (Osborne et al., 1992; Henderson and Osborne, 2000). Daphne's interest in seed germination remained undimmed at this time; a fruitful collaboration with Ivan Boubriak and others on telomeres and DNA repair culminateded in several papers including a notable review (Osborne et al., 2004), while close collaborations with Patricia Berjak led to publications on seed survival in the mangrove Avicennia marina (e.g. Osborne and Berjak, 1997). Daphne's fascination with the highly recalcitrant A. marina grew progressively during her several visits to South Africa, where her talks were highlights of various ‘Desiccation Workshops’. Latterly, and again with Ivan Boubriak, Daphne became interested in the impact on pollen and seeds of radioactive fall-out from the nuclear accident at the Chernobyl nuclear power station in the Ukraine. A paper containing some of this joint work is to be found in this Special Issue (Boubriak et al., 2008) and her contribution to Ukrainian science was marked with an Honorary Professorship from Kiev State University. Even during her final illness, and from her hospital bed, Daphne was correcting proofs of a research paper and animatedly discussing the latest project, which concerned the protective mucous layer of Artemisia sphaerocephala and A. ordosica seeds from the deserts of north-west China. Just 2 months before her death, she renewed her passport and was waiting for a visa to visit the Chinese desert again to make further field observation of these two species. It is fitting that some of this work is contained in one of the papers included in this Special Issue (Huang et al., 2008). These recent collaborations with scientists in China and Ukraine were sponsored by the Royal Society of London, with Daphne taking the project leader role in each case. So, Daphne Osborne never ‘gave up’, never lost her enthusiasm and remained focussed on research throughout her long, distinguished and productive life. She would surely have wished for no more fitting tribute than this volume dedicated to her memory.
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LITERATURE CITED |
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 TOP LITERATURE CITED |
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Abebie B, Lers A, Philosoph-Hadas S, Goren R, Riov J, Meir S. Differential effects of NAA and 2,4-D in reducing floret abscission in Cestrum (Cestrum elegans) cut flowers are associated with their differential activation of Aux/IAA homologous genes. Annals of Botany (2008) 101:249–259.
Bar-Nun M, Sachs T, Mayer AM. A role for IAA in the infection of Arabidopsis thaliana by Orobanche aegyptiaca. Annals of Botany (2008) 101:261–265.
Berjak P, Pammenter NW. From Avicennia to Zizania: seed recalcitrance in perspective. Annals of Botany (2008) 101:213–228.
Boubriak II, Grodzinsky DM, Polischuk VP, Naumenko VD, Gushcha NP, Micheev AN, McCready SJ, Osborne DJ. Adaptation and impairment of DNA repair function in pollen of Betula verrucosa and seeds of Oenothera biennis from differently radionuclide-contaminated sites of Chernobyl. Annals of Botany (2008) 101:267–276.
Ellis PE, Carlisle DB, Osborne DJ. Desert locusts: sexual maturation delayed by feeding on senescent vegetation. Science (1965) 149:546–547.
Henderson J, Osborne DJ. The oil palm in all our lives: how this came about. Endeavour (2000) 24:63–68.[CrossRef][Medline]
Huang ZY, Boubriak I, Osborne DJ, Dong M, Gutterman Y. Possible role of pectin-containing mucilage and dew in repairing embryo DNA of seeds adapted to desert conditions. Annals of Botany (2008) 101:277–283.
Jackson MB. Ethylene-promoted elongation: an adaptation to submergence stress. Annals of Botany (2008) 101:229–248.
McManus MT. Further examination of abscission zone cells as ethylene target cells in higher plants. Annals of Botany (2008) 101:285–292.
Osborne DJ. Acceleration of abscission by a factor produced in senescent leaves. Nature (1955) 176:1161–1163.[CrossRef]
Osborne DJ. Ethylene and plants of aquatic and semi-aquatic environments. Journal of Plant Growth Regulation (1984) a 2:167–185.
Osborne DJ. Concepts of target cells in plant differentiation. Cell Differentiation (1984) b 14:161–169.[CrossRef][Web of Science][Medline]
Osborne DJ, Hallaway HM. The auxin, 2-4-dichlorophenoxyacetic acid as a regulator of protein synthesis and senescence in detached leaves of Prunus. New Phytologist (1964) 63:334–347.[CrossRef][Web of Science]
Osborne DJ, Berjak P. The making of mangroves: the remarkable pioneering role played by seeds of Avicennia marina. Endeavour. (1997) 21:143–147.
Osborne DJ, Jackson MB. Cell separation in plants (1989) Vol. 35. Berlin and Heidelberg: Springer-Verlag. NATO ASI Series H.
Osborne DJ, McManus MT. Hormones, signals and target cells in plant development (2005) Cambridge: Cambridge University Press.
Osborne DJ, Wright M. Gravity induced cell elongation. Proceedings of the Royal Society of London B (1978) 199:551–564.
Osborne DJ, Jackson MB, Milborrow BV. Physiological properties of an abscission accelerator from senescent leaves. Nature New Biology (1972) 240:98–101.[Web of Science][Medline]
Osborne DJ, Henderson J, Corley RHV. Controlling fruit-shedding in the oil palm. Endeavour (1992) 16:173–177.[CrossRef]
Osborne DJ, Boubriak I, Pritchard H, Smith RD. Seed life-span and telomeres. In: The biology of seeds: recent research advances—Nicolas G, Bradford KJ, Côme D, Pritchard HW, eds. (2004) Wallingford, UK: CABI. 301–309.
Qu X-X, Huang Z-Y, Baskin JM, Baskin CC. Effect of temperature, light and salinity on seed germination and radicle growth of the geographically widespread halophyte shrub Halocnemum strobilaceum. Annals of Botany (2008) 101:293–299.
Ridge I, Osborne DJ. Role of peroxidase when hydroxyproline-rich protein in plant cell walls is increased by ethylene. Nature New Biology (1971) 229:205–208.[Web of Science][Medline]
Sargent JA, Sen-Mandi S, Osborne DJ. The loss of desiccation tolerance during germination: an ultrastructural and biochemical approach. Protoplasma (1981) 105:225–239.[CrossRef][Web of Science]
Stange L, Osborne DJ. Cell specificity in auxin- and ethylene-induced ‘supergrowth’ in Riella helicophylla. Planta (1988) 175:341–347.[CrossRef][Web of Science]
Thompson DS. Space and time in the plant cell wall: relationships between cell type, cell wall rheology and cell function. Annals of Botany (2008) 101:203–211.
Thompson DS, Osborne DJ. A role for the stele in intertissue signalling in the initiation of abscission in bean leaves (Phaseolus vulgaris L.). Plant Physiology (1994) 105:341–347.[Abstract]
Yang TF, Gonzalez-Carranza ZH, Maunders MJ, Roberts JA. Ethylene and the regulation of senescence processes in transgenic Nicotiana sylvestris plants. Annals of Botany (2008) 101:301–310.
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