Tracy Valentine
Tracy has over 20 years experience in applied and basic research at the plant root:soils interface. Utilising both image analysis and molecular based methods she has investigated processes and impacts of soil management on plant root growth and development, and root soil biological and physical interactions with the aim of understanding how to improve crop genotypes and management systems, via increasing knowledge of root:soil biological and physical processes at a range of scales.
Current research interests
-
• Understanding how changes in agriculture impact on the performance of crop plants, as well as the impact of the management on soils is key to developing more sustainable farming practices in terms of crop yield, long-term soils sustainability and farm income sustainability.
• Research includes:
o Mechanistic understanding of the individual root elongations
o Phenotyping of root traits including root architecture
o Mechanistic understanding of root interactions with soil structure
o Understanding impact of crop management (e.g. soil tillage and crop rotations) on soil and root:soil interactions
o High resolution and multispectral imaging and image analysis
o Whole plant phenotyping and
o Impact of soil restrictions on plant performance and ecosystem impacts
o Impact of crop cultivar variation on root:soil interactions.
o Utilisation of confocal microscopy and computer vision techniques to develop tools for measuring cell expansion, seed biology and root elongation.
Past research
- Movement, replication and suppression of Tobacco mosaic virus and Tobacco rattle virus in tobacco and Arabidopsis. Utilisation of Tobacco rattle virus as a vector for inducing gene silencing of endogenous root development genes (Mylnefield Research Services).
- Growth and development effects of cell wall carbohydrates (University College London)
Bibliography
- Yassin, M.; Ton, J.; Rolfe, S.A.; Valentine, T.A.; Cromey, M.; Holden, N.J.; Newton, A.C. (In press) The rise, fall and resurrection of chemical-induced resistance agents., Pest Management Science.
- Leybourne, D.J.; Valentine, T.A.; Binnie, K.; Taylor, A.; Karley, A.J.; Bos, J.I.B. (2022) Drought stress increases the expression of barley defence genes with negative consequences for infesting cereal aphids , Journal of Experimental Botany
- George, T.S.; Hawes, C.; Valentine, T.A..; Karley, A.J.; Iannetta, P.; Brooker, R.W. (2022) Harnessing ecological principles and physiological mechanisms in diversifying agricultural systems for sustainability: Experience from studies deploying nature-based solutions in Scotland., Frontiers in Agricultural Science and Engineering, 9, 214-237.
- Leybourne, D.J.; Preedy, K.F.; Valentine, T.A.; Bos, J.I.B.; Karley, A.J. (2021) Drought has negative consequences on aphid fitness and plant vigour: Insights from a meta-analysis., Ecology and Evolution, 11, 11915-11929.
- Brown, J.L.; Stobart, R.; Hallett, P.D.; George, T.S.; Newton, A.C.; Valentine, T.A.; McKenzie, B.M. (2021) Variable impacts of reduced and zero tillage on soil carbon storage across 4-10 years of UK field experiments., Journal of Soils and Sediments, 21, 890-904.
- Newton, A.C.; Guy, D.C.; Valentine, T.A.; McKenzie, B.M.; George, T.S.; Hackett, C.A. (2020) Identifying spring barley cultivars with differential response to tillage., Agronomy, 10, Article No. 686.
- Teixeira, A.; Iannetta, P.P.M.; Binnie, K.; Valentine, T.A.; Toorop, P. (2020) Myxospermous seed-mucilage quantity correlates with environmental gradients indicative of water-deficit stress: Plantago species as a model., Plant and Soil, 446, 343-356.
- Leybourne, D.J.; Valentine, T.A.; Bos J.I.B.; Karley, A.J. (2020) A fitness cost resulting from Hamiltonella defensa infection is associated with altered probing and feeding behaviour in Rhopalosiphum padi., Journal of Experimental Biology, 223, Article No. jeb207936.
- Leybourne, D.J.; Bos, J.I.B.; Valentine, T.A.; Karley, A.J. (2020) The price of protection: a defensive endosymbiont impairs nymph growth in the bird cherry-oat aphid, Rhopalosiphum padi., Insect Science, 27, 69-85.
- Leybourne, D.L.; Valentine, T.A.; Robertson, J.A.H.; Perez-Fernandez, E.; Main, A.M.; Karley, A.J.; Bos, J.I.B. (2019) Defence gene expression and phloem quality contribute to mesophyll and phloem resistance to aphids in wild barley., Journal of Experimental Botany, 70, 4011-4026.
- Dello Jacovo, E.; Valentine, T.A.; Maluk, M.; Toorop, P.; Lopez del Egido, L.; Frachon, N.; Kenicer, G.; Park, L.; Goff, M.; Ferro, V.A.; Bonomi, C.; James, E.K.; Iannetta, P.P.M. (2019) Towards a characterisation of the wild legume bitter vetch (Lathyrus linifolius L. (Reichard) Bässler): heteromorphic seed germination, root nodule structure and N-fixing rhizobial symbionts., Plant Biology, 2, 523-532.
- McKenzie, B.M.; Stobart, R.; Brown, J.L.; George, T.S.; Morris, N.; Newton, A.C.; Valentine, T.A.; Hallett, P.D. (2017) Platforms to test and demonstrate sustainable soil management: integration of major UK field experiments., AHDB Final Report RD-2012-3786, 178pp.
- Greenland, A.G.; Bentley, S.; Jones, H.; Karley, A.; Lee, D.; Sherlock, D.; Valentine, T.; White, C.; Young. P. (2017) New wheat root ideotypes for improved resource use efficiency and yield performance in reduced input agriculture., AHDB Project Report, Reference No. RD-2008-3575.
- Cheng, Y.H.; Jiang, Y.; Wu, Y.; Valentine, T.A.; Li, H.X. (2016) Soil nitrogen status modifies rice root response to nematode-bacteria interactions in the rhizosphere., PLoS ONE, 11, Article No. e0148021.
- Squire, G.R.; Hawes, C.; Valentine, T.A.; Young, M.W. (2015) Degradation rate of soil function varies with trajectory of agricultural intensification., Agriculture, Ecosystems and Environment, 202, 160-167.
- Griffiths, B.S.; Hallett, P.D.; Daniell, T.J.; Hawes, C.; Squire, G.S.; Mitchell, S.M.; Caul, S.; Valentine, T.A.; Binnie, K.; Adeloye, A.J.; Rustum, R.; Nevison, I. (2015) Probing soil physical and biological resilience data from a broad sampling of arable farms in Scotland., Soil Use and Management, 31, 491-503.
- Downie, H.F.; Adu, M.O.; Schmidt, S.; Otten, W.; Dupuy, L.X.; White, P.J.; Valentine, T.A. (2015) Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis., Plant, Cell and Environment, 38, 1213-1232.
- George, T.S.; Hawes, C.; Newton, A.C.; McKenzie, B.M.; Hallett, P.D.; Valentine, T.A. (2014) Field phenotyping and long-term platforms to characterise how crop genotypes interact with soil processes and the environment., Agronomy, 4, 242-278.
- Downie, H.; Valentine, T.A.; Otten, W.; Spiers, A.J.; Dupuy, L.X. (2014) Transparent soil microcosms allow 3D spatial quantification of soil microbiological processes in vivo., Plant Signaling and Behavior, 9, Article No. e29878.
- Haling, R.E.; Brown, L.K.; Bengough, A.G.; Valentine, T.A.; White, P.J.; Young, I.M.; George, T.S. (2014) Root hair length and rhizosheath mass depend on soil porosity, strength and water content in barley genotypes., Planta, 239, 643-651.
- Stobart, R.; Hallett, P.D.; George, T.S.; Morris, N.; Newton, A.C.; Valentine, T.A.; MacKenzie, B.M. (2014) Platforms to test and demonstrate sustainable soil management; integration of major UK field experiments., Crop Production in Southern Britain Meeting: Precision Decision for Profitable Cropping, Peterborough Arena, 25-26 November 2014. Aspects of Applied Biology, 127, 233-239.
- White, P.J.; George, T.S.; Dupuy, L.X.; Karley, A.J.; Valentine, T.A.; Wiesel, L.; Wishart, J. (2013) Root traits for infertile soils., Frontiers in Plant Science, 4, 193.
- Valentine, T.A.; Hallett, P.D.; Binnie, K.; Young, M.W.; Squire, G.R.; Hawes, C.; Bengough, A.G. (2012) Soil strength and macropore volume limit root elongation rates in many UK agricultural soils., Annals of Botany, 110, 259-270.
- Downie, H.; Holden, N.; Otten, W.; Spiers, A.J.; Valentine, T.A.; Dupuy, L.X. (2012) Transparent soil for imaging the rhizosphere., PLoS ONE, 7, Article No. e44276.
- Newton, A.C.; Guy, D.C.; Bengough, A.G.; Gordon, D.C.; McKenzie, B.M.; Sun, B.; Valentine, T.A.; Hallett, P.D. (2012) Soil tillage effects on the efficacy of cultivars and their mixtures in winter barley., Field Crops Research, 128, 91-100.
- Bengough, A.G.; McKenzie, B.M.; Hallett, P.D.; Valentine, T.A. (2011) Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits., Journal of Experimental Botany, 62, 59-68.
- Karley, A.J.; Valentine, T.A.; Squire, G.R. (2011) Dwarf alleles differentially affect barley root traits influencing nitrogen acquisition under low nutrient supply., Journal of Experimental Botany, 62, 3917-3927.
- Wuyts, N.; Bengough, A.G.; Roberts, T.J.; Du, C.; Bransby, M.F.; McKenna, S.J.; Valentine, T.A. (2011) Automated motion estimation of root responses to sucrose in two Arabidopsis thaliana genotypes using confocal microscopy., Planta, 234, 769-784.
- Iannetta, P.P.M.; Begg, G.S.; Valentine, T.A.; Wishart, J. (2010) Sustainable disease control using weeds as indicators: Capsella bursa pastoris and Tobacco Rattle Virus., Weed Research, 50, 511-514.
- Bengough, A.G.; Hans, J.; Bransby, M.F.; Valentine, T.A. (2010) PIV as a method for quantifying root cell growth and particle displacement in confocal images., Microscopy Research and Technique, 73, 27-36.
- Valentine, T.A.; Bengough, A.G.; Hallett, P.D.; McKenzie, B.M. (2010) Root traits for a changing physical environment., Annual Report of the Scottish Crop Research Institute for 2009, pp13-14.
- White, P.J.; Bengough, A.G.; Bingham, I.J.; George, T.S.; Karley, A.J.; Valentine, T.A. (2009) Induced mutations affecting root architecture and mineral acquisition in barley., In: Shu, Q.Y. (ed.). Induced Plant Mutations in the Genomics Era. Food and Agriculture Organisation of the United Nations, Rome, Italy, pp381-384
- Valentine, T.A.; Randall, E.; Wypijewski, K.; Chapman, S.N.; Jones, J.T.; Oparka, K.J. (2007) Delivery of macromolecules to plant parasitic nematodes using a tobacco rattle virus vector., Plant Biotechnology Journal, 5, 827-834.
- Bengough, A.G.; Bransby, M.F.; Hans, J.; McKenna, S.J.; Roberts, T.J.; Valentine, T.A. (2006) Root responses to soil physical conditions; growth dynamics from field to cell., Journal of Experimental Botany, 57, 437-447.
- Iannetta, P.P.M.; Begg, G.S.; Wishart, J.; Young, M.W.; Karley, A.J.; Valentine, T.A.; Hawes, C.; Squire, G.R. (2006) Common wild plants as biodiversity indicators., Annual Report of the Scottish Crop Research Institute for 2006, pp42-43.
- Bengough, A.G.; Hallett, P.D.; McKenzie, B.M.; Valentine, T.A.; Wuyts, N. (2006) Dynamics of root-soil systems., Annual Report of the Scottish Crop Research Institute for 2006, pp40-41.
- Humphris, S.N.; Bengough, A.G.; Griffiths, B.S.; Killham, K.; Rodger, S.; Stubbs, V.; Valentine, T.A.; Young, I.M. (2005) Root cap influences root colonisation by Pseudomonas fluorescens SBW25 on maize., FEMS Microbiology Ecology, 54, 123-130.
- Valentine, T.A.; Shaw, J.; Blok, V.C.; Phillips, M.S.; Oparka, K.J.; Lacomme, C. (2004) Efficient virus-induced gene silencing in roots using a modified tobacco rattle virus vector., Plant Physiology, 136, 3999-4009.
- Bengough, A.G.; Barlow, P.W.; Cooke, D.E.L.; Griffiths, B.S.; Humphris, S.N.; Iijima, M.; Killham, K.; Rodger, S.; Stubbs, V.; Valentine, T.A.; Young, I.M. (2004) Root border cells in plant-soil interactions., Annual Report of the Scottish Crop Research Institute for 2003/2004, 160-161.
- Valentine, T.A.; Roberts, I.M.; Oparka, K.J. (2002) Inhibition of tobacco mosaic virus (TMV) in lateral roots is dependant on the propagation of a meristem-derived signal., Protoplasma, 219, 184-196.
- Leybourne, D.J.; Valentine, T.A.; Binnie, K.; Taylor, A.; Karley, A.J.; Bos, J.I.B. (2022) Drought stress increases the expression of barley defence genes with negative consequences for infesting cereal aphids , Journal of Experimental Botany
- George, T.S.; Hawes, C.; Valentine, T.A..; Karley, A.J.; Iannetta, P.; Brooker, R.W. (2022) Harnessing ecological principles and physiological mechanisms in diversifying agricultural systems for sustainability: Experience from studies deploying nature-based solutions in Scotland., Frontiers in Agricultural Science and Engineering, 9, 214-237.
- Leybourne, D.J.; Preedy, K.F.; Valentine, T.A.; Bos, J.I.B.; Karley, A.J. (2021) Drought has negative consequences on aphid fitness and plant vigour: Insights from a meta-analysis., Ecology and Evolution, 11, 11915-11929.
- Brown, J.L.; Stobart, R.; Hallett, P.D.; George, T.S.; Newton, A.C.; Valentine, T.A.; McKenzie, B.M. (2021) Variable impacts of reduced and zero tillage on soil carbon storage across 4-10 years of UK field experiments., Journal of Soils and Sediments, 21, 890-904.
- Newton, A.C.; Guy, D.C.; Valentine, T.A.; McKenzie, B.M.; George, T.S.; Hackett, C.A. (2020) Identifying spring barley cultivars with differential response to tillage., Agronomy, 10, Article No. 686.
- Teixeira, A.; Iannetta, P.P.M.; Binnie, K.; Valentine, T.A.; Toorop, P. (2020) Myxospermous seed-mucilage quantity correlates with environmental gradients indicative of water-deficit stress: Plantago species as a model., Plant and Soil, 446, 343-356.
- Leybourne, D.J.; Valentine, T.A.; Bos J.I.B.; Karley, A.J. (2020) A fitness cost resulting from Hamiltonella defensa infection is associated with altered probing and feeding behaviour in Rhopalosiphum padi., Journal of Experimental Biology, 223, Article No. jeb207936.
- Leybourne, D.J.; Bos, J.I.B.; Valentine, T.A.; Karley, A.J. (2020) The price of protection: a defensive endosymbiont impairs nymph growth in the bird cherry-oat aphid, Rhopalosiphum padi., Insect Science, 27, 69-85.
- Leybourne, D.L.; Valentine, T.A.; Robertson, J.A.H.; Perez-Fernandez, E.; Main, A.M.; Karley, A.J.; Bos, J.I.B. (2019) Defence gene expression and phloem quality contribute to mesophyll and phloem resistance to aphids in wild barley., Journal of Experimental Botany, 70, 4011-4026.
- Dello Jacovo, E.; Valentine, T.A.; Maluk, M.; Toorop, P.; Lopez del Egido, L.; Frachon, N.; Kenicer, G.; Park, L.; Goff, M.; Ferro, V.A.; Bonomi, C.; James, E.K.; Iannetta, P.P.M. (2019) Towards a characterisation of the wild legume bitter vetch (Lathyrus linifolius L. (Reichard) Bässler): heteromorphic seed germination, root nodule structure and N-fixing rhizobial symbionts., Plant Biology, 2, 523-532.
- Cheng, Y.H.; Jiang, Y.; Wu, Y.; Valentine, T.A.; Li, H.X. (2016) Soil nitrogen status modifies rice root response to nematode-bacteria interactions in the rhizosphere., PLoS ONE, 11, Article No. e0148021.
- Squire, G.R.; Hawes, C.; Valentine, T.A.; Young, M.W. (2015) Degradation rate of soil function varies with trajectory of agricultural intensification., Agriculture, Ecosystems and Environment, 202, 160-167.
- Griffiths, B.S.; Hallett, P.D.; Daniell, T.J.; Hawes, C.; Squire, G.S.; Mitchell, S.M.; Caul, S.; Valentine, T.A.; Binnie, K.; Adeloye, A.J.; Rustum, R.; Nevison, I. (2015) Probing soil physical and biological resilience data from a broad sampling of arable farms in Scotland., Soil Use and Management, 31, 491-503.
- Downie, H.F.; Adu, M.O.; Schmidt, S.; Otten, W.; Dupuy, L.X.; White, P.J.; Valentine, T.A. (2015) Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis., Plant, Cell and Environment, 38, 1213-1232.
- George, T.S.; Hawes, C.; Newton, A.C.; McKenzie, B.M.; Hallett, P.D.; Valentine, T.A. (2014) Field phenotyping and long-term platforms to characterise how crop genotypes interact with soil processes and the environment., Agronomy, 4, 242-278.
- Downie, H.; Valentine, T.A.; Otten, W.; Spiers, A.J.; Dupuy, L.X. (2014) Transparent soil microcosms allow 3D spatial quantification of soil microbiological processes in vivo., Plant Signaling and Behavior, 9, Article No. e29878.
- Haling, R.E.; Brown, L.K.; Bengough, A.G.; Valentine, T.A.; White, P.J.; Young, I.M.; George, T.S. (2014) Root hair length and rhizosheath mass depend on soil porosity, strength and water content in barley genotypes., Planta, 239, 643-651.
- Stobart, R.; Hallett, P.D.; George, T.S.; Morris, N.; Newton, A.C.; Valentine, T.A.; MacKenzie, B.M. (2014) Platforms to test and demonstrate sustainable soil management; integration of major UK field experiments., Crop Production in Southern Britain Meeting: Precision Decision for Profitable Cropping, Peterborough Arena, 25-26 November 2014. Aspects of Applied Biology, 127, 233-239.
- White, P.J.; George, T.S.; Dupuy, L.X.; Karley, A.J.; Valentine, T.A.; Wiesel, L.; Wishart, J. (2013) Root traits for infertile soils., Frontiers in Plant Science, 4, 193.
- Valentine, T.A.; Hallett, P.D.; Binnie, K.; Young, M.W.; Squire, G.R.; Hawes, C.; Bengough, A.G. (2012) Soil strength and macropore volume limit root elongation rates in many UK agricultural soils., Annals of Botany, 110, 259-270.
- Downie, H.; Holden, N.; Otten, W.; Spiers, A.J.; Valentine, T.A.; Dupuy, L.X. (2012) Transparent soil for imaging the rhizosphere., PLoS ONE, 7, Article No. e44276.
- Newton, A.C.; Guy, D.C.; Bengough, A.G.; Gordon, D.C.; McKenzie, B.M.; Sun, B.; Valentine, T.A.; Hallett, P.D. (2012) Soil tillage effects on the efficacy of cultivars and their mixtures in winter barley., Field Crops Research, 128, 91-100.
- Bengough, A.G.; McKenzie, B.M.; Hallett, P.D.; Valentine, T.A. (2011) Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits., Journal of Experimental Botany, 62, 59-68.
- Karley, A.J.; Valentine, T.A.; Squire, G.R. (2011) Dwarf alleles differentially affect barley root traits influencing nitrogen acquisition under low nutrient supply., Journal of Experimental Botany, 62, 3917-3927.
- Wuyts, N.; Bengough, A.G.; Roberts, T.J.; Du, C.; Bransby, M.F.; McKenna, S.J.; Valentine, T.A. (2011) Automated motion estimation of root responses to sucrose in two Arabidopsis thaliana genotypes using confocal microscopy., Planta, 234, 769-784.
- Iannetta, P.P.M.; Begg, G.S.; Valentine, T.A.; Wishart, J. (2010) Sustainable disease control using weeds as indicators: Capsella bursa pastoris and Tobacco Rattle Virus., Weed Research, 50, 511-514.
- Bengough, A.G.; Hans, J.; Bransby, M.F.; Valentine, T.A. (2010) PIV as a method for quantifying root cell growth and particle displacement in confocal images., Microscopy Research and Technique, 73, 27-36.
- Valentine, T.A.; Randall, E.; Wypijewski, K.; Chapman, S.N.; Jones, J.T.; Oparka, K.J. (2007) Delivery of macromolecules to plant parasitic nematodes using a tobacco rattle virus vector., Plant Biotechnology Journal, 5, 827-834.
- Bengough, A.G.; Bransby, M.F.; Hans, J.; McKenna, S.J.; Roberts, T.J.; Valentine, T.A. (2006) Root responses to soil physical conditions; growth dynamics from field to cell., Journal of Experimental Botany, 57, 437-447.
- Humphris, S.N.; Bengough, A.G.; Griffiths, B.S.; Killham, K.; Rodger, S.; Stubbs, V.; Valentine, T.A.; Young, I.M. (2005) Root cap influences root colonisation by Pseudomonas fluorescens SBW25 on maize., FEMS Microbiology Ecology, 54, 123-130.
- Valentine, T.A.; Shaw, J.; Blok, V.C.; Phillips, M.S.; Oparka, K.J.; Lacomme, C. (2004) Efficient virus-induced gene silencing in roots using a modified tobacco rattle virus vector., Plant Physiology, 136, 3999-4009.
- Valentine, T.A.; Roberts, I.M.; Oparka, K.J. (2002) Inhibition of tobacco mosaic virus (TMV) in lateral roots is dependant on the propagation of a meristem-derived signal., Protoplasma, 219, 184-196.
- Gillespie, T.; Boevink, P.; Haupt, S.; Roberts, A.G.; Toth, R.; Valentine, T.A.; Chapman, S.N.; Oparka, K.J. (2002) Functional analysis of a DNA-shuffled movement protein reveals that microtubules are dispensable for the cell-to-cell movement of tobacco mosaic virus., Plant Cell, 14, 1207-1222.
- White, P.J.; Bengough, A.G.; Bingham, I.J.; George, T.S.; Karley, A.J.; Valentine, T.A. (2009) Induced mutations affecting root architecture and mineral acquisition in barley., In: Shu, Q.Y. (ed.). Induced Plant Mutations in the Genomics Era. Food and Agriculture Organisation of the United Nations, Rome, Italy, pp381-384
- McKenzie, B.M.; Stobart, R.; Brown, J.L.; George, T.S.; Morris, N.; Newton, A.C.; Valentine, T.A.; Hallett, P.D. (2017) Platforms to test and demonstrate sustainable soil management: integration of major UK field experiments., AHDB Final Report RD-2012-3786, 178pp.
- Greenland, A.G.; Bentley, S.; Jones, H.; Karley, A.; Lee, D.; Sherlock, D.; Valentine, T.; White, C.; Young. P. (2017) New wheat root ideotypes for improved resource use efficiency and yield performance in reduced input agriculture., AHDB Project Report, Reference No. RD-2008-3575.
- Valentine, T.A.; Bengough, A.G.; Hallett, P.D.; McKenzie, B.M. (2010) Root traits for a changing physical environment., Annual Report of the Scottish Crop Research Institute for 2009, pp13-14.
- Iannetta, P.P.M.; Begg, G.S.; Wishart, J.; Young, M.W.; Karley, A.J.; Valentine, T.A.; Hawes, C.; Squire, G.R. (2006) Common wild plants as biodiversity indicators., Annual Report of the Scottish Crop Research Institute for 2006, pp42-43.
- Bengough, A.G.; Hallett, P.D.; McKenzie, B.M.; Valentine, T.A.; Wuyts, N. (2006) Dynamics of root-soil systems., Annual Report of the Scottish Crop Research Institute for 2006, pp40-41.
- Bengough, A.G.; Barlow, P.W.; Cooke, D.E.L.; Griffiths, B.S.; Humphris, S.N.; Iijima, M.; Killham, K.; Rodger, S.; Stubbs, V.; Valentine, T.A.; Young, I.M. (2004) Root border cells in plant-soil interactions., Annual Report of the Scottish Crop Research Institute for 2003/2004, 160-161.
- Valentine, T.A.; Dorward, M.; Oparka, K.J. (1999) The silence of the RAMs - viral suppression in root apical meristems., Annual Report of the Scottish Crop Research Institute for 1999/2000, pp132-135.