Prof Howard Thomas

Prof Howard Thomas

Emeritus Professor

Contact Details


Investigation and modification of cellular and biochemical mechanisms of plant senescence and death, with special emphasis on pigment and protein metabolism.

Cloning, mapping and exploiting genes determining senescence, late-season and post-harvest deterioration, food, feed and bioprocessing quality and consumer perception in a range of crop and amenity species.

Use of imaging and machine-learning methods for non-destructive analysis of plant development and remote field to landscape-level monitoring of crops and ecosystems.

Cultural significance of scientific research and promotion of links between science and the arts.



Thomas, H., Ougham, H. 2016. Introduction to a Virtual Issue on plant senescence. New Phytologist 212 (3) pp. 531-536.

Thomas, H., Archer, J.E.E., Marggraf Turley, R. 2016. Remembering Darnel, a Forgotten Plant of Literary, Religious, and Evolutionary Significance. Journal of Ethnobiology 36 (1) pp. 29-44.


Archer, J.E.E., Thomas, H., Marggraf Turley, R. 2015. Reading Shakespeare with the grain: sustainability and the hunger business. Green Letters: Studies in Ecocriticism 19 (1) pp. 8-20.

Archer, J.E.E., Marggraf Turley, R., Thomas, H. 2015. Soper at oure aller cost: The Politics of Food Supply in the Canterbury Tales. The Chaucer Review 50 (1 & 2) pp. 1-29. Cadair


Marggraf Turley, R.J., Archer, J.E.E., Thomas, H. 2014. Food and the Literary Imagination. Springer Nature, Basingstoke

Chew, Y.H., Wenden, B., Flis, A., Mengin, V., Taylor, J., Davey, C.L., Tindal, C., Thomas, H., Ougham, H.J., De Reffye, P., Stitt, M., Williams, M., Muetzelfeldt, R., Halliday, K.J., Millar, A.J. 2014. Multiscale digital Arabidopsis predicts individual organ and whole-organism growth. Proceedings of the National Academy of Sciences of the United States of America 111 (39) pp. E4127-E4136. Cadair

Thomas, H., Ougham, H.J. 2014. The stay-green trait. Journal of Experimental Botany 65 pp. 3889-3900. Cadair


Archer, J.E., Marggraf Turley, R.J., Thomas, H. 2013. Reading with the Grain: Sustainability and the Literary Imagination. 2013 INSPIRE Lecture on Literature and Sustainability. 2013 INSPIRE Lecture on Literature and Sustainability, Lampeter, United Kingdom of Great Britain and Northern Ireland, 23/05/2013. Prifysgol Cymru Y Drindod Dewi Sant, Lampeter Other


Marggraf Turley, R., Archer, J.E.E., Thomas, H. 2012. Keats's Prospects. Times Literary Supplement pp. 14-15.

Marggraf Turley, R., Archer, J.E., Thomas, H. 2012. On St Giles Hill- Keats’s Ode “To Autumn’ in the Market. Times Literary Supplement pp. 14-15.

Archer, J.E., Turley, R.M., Thomas, H. 2012. The Autumn King: Remembering the Land in King Lear. Shakespeare Quarterly 63 (4) pp. 518-543. Cadair


Robson, P.R.H., Kelly, R., Jensen, E.F., Giddings, G.D., Leitch, M., Davey, C., Gay, A.P., Jenkins, G., Thomas, H., Donnison, I.S. 2011. A flexible quantitative methodology for the analysis of gene-flow between conventionally bred maize populations using microsatellite markers. Theoretical and Applied Genetics 122 (4) pp. 819-829. Cadair

Thomas, H., Archer, J.E., Marggraf Turley, R. 2011. Evolution, Physiology and Phytochemistry of the Psychotoxic Arable Mimic Weed Darnel (Lolium temulentum L.). In U. E. Lüttge., W. Beyschlag., B. Büdel., D. Francis. (eds) Progress in Botany. Springer Nature pp. 73-104. Cadair


Marggraf Turley, R., Thomas, H., Archer, J.E. 2010. A Tragedy of Idle Weeds: Why Grigori Kozintsev's Lear is more faithful to Shakespeare's 'arable play' than most modest stagings. Times Literary Supplement pp. 14-15.

Mur, L.A.J., Aubry, S., Mondhe, M., Kingston-smith, A., Gallagher, J., Timms-taravella, E., James, C., Papp, I., Hörtensteiner, S., Thomas, H., Ougham, H. 2010. Accumulation of chlorophyll catabolites photosensitizes the hypersensitive response elicited by Pseudomonas syringae in Arabidopsis. New Phytologist 188 (1) pp. 161-174.

Raven, J., Thomas, H. 2010. Grasses. Current Biology 20 (19) pp. R837-R839. Cadair


Thomas, H., Huang, L., Young, M., Ougham, H.J. 2009. Evolution of plant senescence. BMC Evolutionary Biology 9 (163) 163 Cadair

2009. Faecal Markers - Markers developed to optimise visualisation of faecal contamination on animal carcasses in the abattoir.

Jones, R.N., Thomas, H.Naganowska, B., Kachlick, P.i., Krajewski, P. 2009. Genome restructuring in hybrids: marriages of inconvenience. pp. pp11-28. Other

Davey, C., Ougham, H.J., Millar, A., Thomas, H., Tindal, C., Muetzelfeldt, R. 2009. Making crop and plant mathematical models easily accessible to the plant science and systems biology communities.

Jones, R.N., Ougham, H.J., Thomas, H., Pasakinskiene, I.S. 2009. Markers and mapping revisited: finding your gene. New Phytologist 183 (4) pp. 935-966. Cadair

Ougham, H.J., Millar, A., Muetzelfeldt, R., Tindal, C., Thomas, H., Davey, C. 2009. PlaSMo: Making existing plant and crop mathematical models available to plant systems biologists. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology pp. 225-. Cadair

Davey, C., Ougham, H.J., Millar, A., Thomas, H., Tindal, C., Muetzelfeldt, R. 2009. PlasMo: Making existing plant and crop mathematical models available to plant systems biologist. Aspects 93: Integrated Agricultural Systems. Association of Applied Biologists Conference on Integrated Agricultural Systems: Methodologies, Modelling and Measuring, Edinburgh, United Kingdom of Great Britain and Northern Ireland, 02/06/2009 - 04/06/2009. pp. S225-S226.

Archetti, M., Doring, T.F., Hagen, S.B., Hughes, N.M., Leather, S.R., Lee, D.W., Lev-Yadun, S., Manetas, Y., Ougham, H.J., Schaberg, P.G., Thomas, H. 2009. Response to Sinkkonen: Ultraviolet reflectance in autumn leaves and the un-naming of colours. Trends in Ecology and Evolution 24 (5) pp. 237-238. Cadair

Doring, T.F., Lev-Yadun, S., Ougham, H.J., Leather, S.R., Schaberg, P.G., Archetti, M., Manetas, Y., Thomas, H., Lee, D.W., Hagen, S.B., Hughes, N.M. 2009. Unravelling the evolution of autumn colours: an interdisciplinary approach. Trends in Ecology and Evolution 24 (3) pp. 166-173. Cadair


Turner, L.B., Cairns, A.J., Armstead, I.P., Thomas, H., Humphreys, M.W., Humphreys, M.O. 2008. Does fructan have a functional role in physiological traits? Investigation by quantative trait locus mapping. New Phytologist 179 (3) pp. 765-775. Cadair Other

Gay, A.P., Thomas, H., Roca, M., James, C.L., Taylor, J., Rowland, J.J., Ougham, H.J. 2008. Nondestructive analysis of senescence in mesophyll cells by spectral resolution of protein synthesis-dependent pigment metabolism. New Phytologist 179 (3) pp. 663-674. Cadair Other

Thomas, H., Jansson, S. 2008. Senescence: developmental program or timetable? New Phytologist 179 (3) pp. 575-579. Cadair

Thomas, H. 2008. Systems biology and the biology of systems: how, if at all, are they related? New Phytologist 177 (1) pp. 11-15. Cadair

Thomas, H., Ougham, H.J., Archetti, M. 2008. The adaptive value of leaf colour. New Phytologist 179 pp. 9-13. Cadair Other

Ougham, H.J., Hortensteiner, S., Armstead, I.P., Donnison, I.S., King, I.P., Thomas, H., Mur, L.A.J. 2008. The control of chlorophyll catabolism and the status of yellowing as a biomarker of leaf senescence. Plant Biology 10 (S1) pp. 4-14. Cadair Other


Armstead, I.P., Donnison, I.S., Aubry, S., Harper, J.A., Hörtensteiner, S., James, C.L., Mani, J., Moffet, M., Ougham, H.J., Roberts, L.A., Thomas, A.M., Weeden, N., Thomas, S., King, I.P. 2007. Cross-species identification of Mendel's/locus. Science 315 (5808) pp. 73. Other Cadair

Donnison, I., Gay, A., Thomas, H., Edwards, K.J., Edwards, D., Evans, C., Thomas, A., Ougham, H. 2007. Modification of nitrogen remobilisation, grain fill and leaf senescence in maize (Zea mays L.) by transposon insertional mutagenensis in a protease gene. New Phytologist 173 (3) pp. 481-494. Other Cadair

Armstead, I.P., Huang, L.S., King, J., Ougham, H.J., Thomas, H., King, I.P. 2007. Rice pseudomolecule-anchored cross-species DNA sequence alignments indicate regional genomic variation in expressed sequence conservation. BMC Genomics 8 (283) 16 Cadair

Donnison, I.S., Thomas, H., Armstead, I.P., Ougham, H.J., Howarth, C.J., Galyuon, I.K.A. 2007. The genetic control of senescence revealed by mapping quantitative trait loci. In S. Gan. (ed) Annual Plant Reviews: Senescence Processes in Plants. Wiley pp. 171-201. Cadair Other

Mur, L., Mondhe, M., Papp, I., Holton, N., Hoertensteiner, S., Kingston-Smith, A., Thomas, H., Ougham, H. 2007. Throwing new light on the hypersensitive response. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology 146 (4) C2.9 Abstracts of the Annual Main Meeting of the Society for Experimental Biology, Glasgow, United Kingdom of Great Britain and Northern Ireland, 31/03/2007 - 04/04/2007.


Armstead, I.P., Donnison, I.S., Aubry, S., Harper, J.A., Hortensteiner, S., James, C.L., Mani, J., Moffet, M., Ougham, H.J., Roberts, L.A., Thomas, A.M., Weeden, N., Thomas, S., King, I.P. 2006. From crop to model to crop: identifying the genetic basis of the staygreen mutation in the Lolium/Festuca forage and amenity grasses. New Phytologist 172 (4) pp. 592-597. Cadair


Ernst, E., Thomas, H., Canter, P.H. 2005. Bringing medicinal plants into cultivation: opportunities and challenges for biotechnology. Trends in Biotechnology 23 (4) pp. 180-185. Cadair

Donnison, I.S., O'Sullivan, D.M., Thomas, A., Canter, P., Moore, B., Armstead, I., Thomas, H., Edwards, K.J., King, I.P. 2005. Construction of a Festuca pratensis BAC library for map-based cloning in IFestulolium substitution lines. Theoretical and Applied Genetics 110 (5) pp. 846-851. Other Cadair

Taylor, J., Moore, B.J., Rowland, J.J., Thomas, H., Ougham, H.J. 2005. Discriminating stay-green grasses using hyperspectral imaging and chemometrics. In M. O. Humphreys. (ed) Molecular breeding for the genetic improvement of forage crops and turf. Wageningen Academic Publishers pp. 120. Cadair Other Other

Merry, R.J., Leemans, D.K., Kingston-Smith, A.H., Theodorou, M.K., Thomas, H. 2005. Evidence in support of a role for plant-mediated proteolysis in the rumens of grazing animals. British Journal of Nutrition pp. 73-79. Other Cadair

King, I.P., King, J., Armstead, I.P., Harper, J.A., Roberts, L.A., Thomas, H., Ougham, H.J., Jones, R.N., Thomas, A.M., Moore, B.J.Humphreys, M.O. 2005. Introgression mapping in the grasses. The 4th international symposium on the molecular breeding of forage and turf, a satellite workshop of the XXth International Grassland Congress, Aberystwyth, United Kingdom of Great Britain and Northern Ireland, 26/06/2005 - 02/07/2005. pp. 31-41. Cadair

Thomas, A.M., Thomas, H., Armstead, I.P., King, I.P., Harper, J.A., Moore, B.J., Huang, L.S., Fentem, P.A., Ougham, H.J., Jones, R.N., Jones, T.A.H., Roberts, L.A., King, J., Donnison, I.S. 2005. Molecular tagging of a senescence gene by introgression mapping of a stay-green mutation from Festuca pratensis. New Phytologist 165 (3) pp. 801-806. Other Cadair

Ougham, H.J., Thomas, H., Morris, P.Schatten, G.P. 2005. The colour of autumn leaves as symptoms of cellular recycling and defences against environmental stresses. Current Topics in Developmental Biology 66 pp. 135-160. Cadair


Pruzinská, A., Hörtensteiner, S., Thomas, H., Ougham, H.J., Roca, M., James, C.L. 2004. Analysis of the chlorophyll catabolism pathway in leaves of an introgression senescence mutant of Lolium temulentum. Phytochemistry pp. 1231-1238. Cadair

Ougham, H.J., Hortensteiner, S., Roca, M., Thomas, H., James, C.L.Dufossel, L. 2004. Chlorophylls and their breakdown in green plant tissues: genetic and environmental control. pp. 8-10. Cadair Other

Armstead, I., Roderick, H.W., Harper, J.A., Thomas, H.M., King, I.P., Humphreys, M.O. 2004. Identification of molecular markers for crown rust (Puccinia coronata) resistance in a Lolium/Festuca introgression population using syntenic relationships with rice. Plant Genomics European Meeting, Lyon, France, 22/09/2004 - 25/09/2004.

Robson, P.R.H., Donnison, I.S., Wang, K., Frame, B., Pegg, S.E., Thomas, A.M., Thomas, H. 2004. Leaf senescence is delayed in maize expressing the Agrobacterium IPT gene under the control of a novel maize senescence-enhanced promoter. Plant Biotechnology Journal 2 (2) pp. 101-112. Cadair

Li, Q., Robson, P.R.H., Bettany, A.J.E., Donnison, I.S., Thomas, H., Scott, I.M. 2004. Modification of senescence in ryegrass transformed with IPT under the control of a monocot senescence-enhanced promoter. Plant Cell Reports 22 (11) pp. 816-821. Cadair


Wagstaff, C., Thomas, H., Ougham, H.J., Stead, A.J. 2003. Defining senescence and death. Journal of Experimental Botany 54 (385) pp. 1127-1132. Cadair Other

Thomas, H. 2003. Do green plants age and, if so, how? Topics in Current Genetics. Springer Nature pp. 145-171. Cadair Other


Thomas, H. 2002. Ageing in plants. Mechanisms of Ageing and Development 123 (7) British Society for Research on Ageing / Institute of Biologists Meeting, London, United Kingdom of Great Britain and Northern Ireland, 25/03/2002 - 26/03/2002. pp. 747–753. Cadair

Harper, J.A., Armstead, I., King, I.P., Roberts, L., Schledde, T., Wagner, N., Thomas, H. 2002. Developing a chromosome substitution series in Lolium/Festuca. 2002 Plant Science Wales, Bangor, United Kingdom of Great Britain and Northern Ireland, 07/01/2002 - 08/01/2002.

Macduff, J.H., Thomas, H., Humphreys, M.O. 2002. Effects of a stay-green mutation on plant nitrogen relations in Lolium perenne during N starvation and after defoliation. Annals of Botany pp. 11-21. Other Cadair

Ougham, H.J., Canter, P.H., Donnison, I.S., Thomas, H.Lea, P.J., Morot-Gaudry, J.F., Hirel, B. 2002. What stay-green mutants tell us about nitrogen remobilization in leaf senescence. Journal of Experimental Botany pp. 801-808. Cadair Other


Thomas, H., Morgan, W.G., Humphreys, M., Harper, J.A., Armstead, I., Moore, B., King, J., Roberts, L., James, A., Humphreys, J., Hawkins, S.L., King, I.P. 2001. Introgression mapping - the route to designer breeding in grasses. Proceedings of the XVIth EUCARPIA Congress. XVIth EUCARPIA Congress, Edinburgh, United Kingdom of Great Britain and Northern Ireland, 10/09/2001 - 14/09/2001. , Edinburgh, Scotland pp. 139-145.

King, J., Thomas, H.M., Armstead, I., Jones, R.N., Kearsey, M.J., Roberts, L.A., Morgan, W.G., King, I.P. 2001. Introgression mapping reveals a 1:1 correspondence between chiasma frequency and genetic distance. 9th International Plant and Animal Genome Meeting, California, United States of America, 13/01/2001 - 17/01/2001. pp. 134.

Jones, A.M., Coimbra, S., Fath, A., Sottomayor, M., Thomas, H. 2001. Programmed cell death assays for plants. In L. M. Schwartz., J. D. Ashwell. (eds) Apoptosis: Cell Death. Methods in Cell Biology Elsevier pp. 437-451. Cadair

Thomas, H., Ougham, H.J., Hortensteiner, S. 2001. Recent advances in the cell biology of chlorophyll catabolism. Advances in Botanical Research 35 pp. 1-52. Cadair

Sadras, V.O., Thomas, H. 2001. The capture and gratuitous disposal of resources by plants. Functional Ecology pp. 3-12. Cadair


Hörtensteiner, S., Chinner, J., Matile, P., Thomas, H., Donnison, I. 2000. Chlorophyll breakdown in Chlorella protothecoides: characterization of degreening and cloning of degreening-related genes. Plant Molecular Biology 42 (3) pp. 439-450.

Langdon, T., Seago, C.M., Jones, R.N., Ougham, H., Thomas, H., Forster, J.W., Jenkins, G. 2000. De Novo Evolution of Satellite DNA on the Rye B Chromosome. Genetics 154 (2) pp. 869-884. Other

Langdon, T., Seago, C.M., Mende, M., Leggett, J.M., Thomas, H., Forster, J.W., Thomas, H., Jones, R.N., Jenkins, G. 2000. Retrotransposon Evolution in Diverse Plant Genomes. Genetics 156 (1) pp. 313-325. Other

King, I., Morgan, W.G., Armstead, I., Jones, T.A.H., Jones, R.N., Harper, J., Roberts, L., Taylor, S., Thomas, H. 2000. Species relationships, introgression and physical mapping in Lolium perenne x Festuca pratensis hybrids. In E. Olmo., C. A. Redi. (eds) Chromosomes Today: Proceedings 13th International Chromosome Conference. Proceedings 13th International Chromosome Conference, Ancona, Italy, 08/09/1998 - 12/09/1998. Springer Nature pp. 277-286.


Cresswell, A., Sackville Hamilton, N.R., Thomas, H., Charnock, R.B., Cookson, A.R., Thomas, B.J. 1999. Evidence for root contraction in white clover (Trifolium repens L.). Annals of Botany 84 (3) pp. 359-369.


King, I.P., Morgan, W.G., Armstead, I.P., Harper, J.A., Hayward, M.D., Bollard, A., Nash, J.V., Forster, J.W., Thomas, H.M. 1998. Introgression mapping in the grasses. I. Introgression of Festuca pratensis chromosomes and chromosome segments into Lolium perenne. Heredity 81 (4) pp. 462-467.

Humphreys, M.W., Pasakinskiene, I., James, A.R., Thomas, H. 1998. Physically mapping quantitative traits for stress resistance in the forage grasses. Journal of Experimental Botany 49 (327) pp. 1611-1618.


Kingston-Smith, A.H., Thomas, H., Foyer, C.H. 1997. Chlorophyll a fluorescence and antioxidant analyses provide evidence for the operation of alternative electron sinks during leaf senescence in a stay-green mutant of Festuca pratensis. Plant, Cell and Environment 20 (11) pp. 1323.

Thomas, H., Evans, C., Thomas, H.M., Humphreys, M.W., Morgan, W.G., Hauck, B., Donnison, I. 1997. Introgression, tagging and expression of a leaf senescence gene in Festulolium. New Phytologist 137 (1) pp. 29-34.

Hauck, B., Gay, A., Macduff, J., Griffiths, C.M., Thomas, H. 1997. Leaf senescence in a non-yellowing mutant of Festuca pratensis: implications of the stay-green mutation for photosynthesis, growth and nutrition . Plant, Cell and Environment 20 (8) pp. 1007-1018.


Gay, A., Thomas, H. 1995. Leaf development in Lolium temulentum: photosynthesis in relation to growth and senescence. New Phytologist 160 (2) pp. 159-168.

Souriau, N., Hauck, B., Gay, A., Foyer, C.H., Thomas, H. 1995. Photosynthesis and light energy dissipation in senescing leaves of grass mutants blocked in chlorophyll degradation. In P. Mathis. (ed) Photosynthesis: From Light to Biosphere. Springer Nature pp. 953-956.


Leggett, J.M., Thomas, H.M., Meredith, M.R., Humphreys, M.W., Morgan, W.G., King, I.P. 1994. Intergenomic translocations and the genomic composition of Avena maroccana Gdgr. revealed by FISH. Chromosome Research 2 (2) pp. 163-164.


Gay, A., Mae, T., Thomas, H. 1993. Effect of light intensity during senescence on photosynthesis and photosynthetic proteins of Lolium temulentum. In D. Wilson., H. Thomas., K. Pithan. (eds) Crop Adaptation to Cool, Wet Climates. EC COST 814 Workshop, Aberystwyth, United Kingdom of Great Britain and Northern Ireland, 23/03/1993 - 24/03/1993. pp. 159-166.

Mae, T., Thomas, H., Gay, A., Makino, A., Hidema, J. 1993. Leaf Development in Lolium temulentum: Photosynthesis and Photosynthetic Proteins in Leaves Senescing under Different Irradiances. Plant and Cell Physiology pp. 391-399.