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Hydrothermal time analysis of tomato seed germination at suboptimal temperature and reduced water potential

Published online by Cambridge University Press:  19 September 2008

Peetambar Dahal  and
Kent J. Bradford
Peetambar Dahal
Affiliation:
Department of Vegetable Crops, University of California, Davis, CA 95616–8631, USA
Kent J. Bradford*
Affiliation:
Department of Vegetable Crops, University of California, Davis, CA 95616–8631, USA
*
* Correspondence
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Abstract

Both temperature (T) and water potential (ψ) have consistent and quantifiable effects on the rate and extent of seed germination (radicle emergence). Germination at suboptimal T can be characterized on the basis of thermal time, or the T in excess of a base (Tb) multiplied by the time to a given percentage germination (tg). Similarly, germination at reduced ψ can be characterized on a hydrotime basis, or the ψ in excess of a base (ψb) multiplied by tg. Within a seed population, the variation in thermal times to germination for a specific percentage (g) is based upon the normal distribution of ψb values among seeds (ψb(g)). Germination responses across a range of suboptimal T and ψ might be accounted for by a general hydrothermal time model incorporating both T and ψ components. We tested this hypothesis for tomato (Lycopersicon esculentum Mill.) seeds of two genotypes differing in germination rates and tolerance of suboptimal T and ψ. For combinations of T (10−25°C) and ψ (0 to −0.9 MPa), a general hydrothermal time model accounted for approximately 75% of the variation in times to germination within the seed populations of both genotypes, and over 96% of the variation in median germination rates. However, ψb(g) distributions were sensitive to both the T and ψ of imbibition, resulting in a poor fit of the model to specific time course data. Analysis of germination timing separately for low and high ψ ranges within a given T resulted in specific models accounting for 88−99% of the variation in individual germination times and >99% of the variation in madian germination rates. Thus, for a given T and ψ range, the hydrotime model closely matched tomato seed germination time courses. Accumulated hydrothermal time accounted well for germination rates at ψ> −0.5 MPa across suboptimal T if ψb(g) was allowed to vary with T. Germination did not show a consistent response to T at ψ < −0.5 MPa, and estimated Tb values varied over different T ranges. Generalization of the hydrothermal time model across the entire range of suboptimal T and ψ was limited by physiological adjustments of the seeds to their current environment. The hydrothermal time model detected and quantified these adjustment processes that would otherwise not be evident from inspection of germination time courses. Temperature and water potential influence the time to germination via physiological mechanisms that reciprocally interact.

Keywords

HydrotimeLycopersicon esculentum Millseed germinationthermal timetemperaturetomatowater potential
Type
Research Papers
Information
Seed Science Research , Volume 4 , Issue 2 , June 1994 , pp. 71 - 80
Copyright
Copyright © Cambridge University Press 1994

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References

Battaglia, M. (1993) Seed germination physiology of Eucalyptus delegatensis R.T. Baker in Tasmania. Australian Journal of Botany 41, 119–136.Google Scholar
Bierhuizen, J.F. and Wagenvoort, W.A. (1974) Some aspects of seed germination in vegetables. The determination and application of heat sums and minimum temperatures for germination. Scientia Horticulturae 2, 213–219.Google Scholar
Bradford, K.J. (1990) A water relations analysis of seed germination rates. Plant Physiology 94, 840–849.Google Scholar
Bradford, K.J. (1994) Water relations in seed germination. In press in Kigel, J. and Negbi, M. (Eds) Seed development and germination. New York, Marcel Dekker.Google Scholar
Bradford, K.J. and Somasco, O.A. (1994) Water relations of lettuce seed thermoinhibition. I. Priming and endosperm effects on base water potential. Seed Science Research 4, 1–10.CrossRefGoogle Scholar
Bradford, K.J., Dahal, P. and Ni, B.R. (1993) Quantitative models describing germination responses to temperature, water potential, and growth regulators, pp 239–248 in Côme, D. and Corbineau, F. (Eds) Proceedings, fourth international workshop on seeds: Basic and applied aspects of seed biology. Paris, Association pour la Formation Professionals de l'lnterprofession Semences.Google Scholar
Coolbear, P. and McGill, C.R. (1990) Effects of a low-temperature pre-sowing treatment on the germination of tomato seed under temperature and osmotic stress. Scientia Horticulturae 44, 43–54.CrossRefGoogle Scholar
Covell, S., Ellis, R.H., Roberts, E.H. and Summerfield, R.J. (1986) The influence of temperature on seed germination rate in grain legumes. I. A comparison of chickpea, lentil, soybean and cowpea at constant temperatures. Journal of Experimental Botany 37, 705–715.Google Scholar
Dahal, P. and Bradford, K.J. (1990) Effects of priming and endosperm integrity on germination rates of tomato genotypes. II: Germination at reduced water potential. Journal of Experimental Botany 41, 1441–1453.CrossRefGoogle Scholar
Dahal, P., Bradford, K.J. and Jones, R.A. (1990) Effects of priming and endosperm integrity on germination rates of tomato genotypes. I. Germination at suboptimal temperature. Journal of Experimental Botany 41, 1431–1439.Google Scholar
Dahal, P., Bradford, K.J. and Haigh, A.M. (1993) The concept of hydrothermal time in seed germination and priming, pp. 1009–1014 in Côme, D. and Corbineau, F. (Eds) Proceedings, fourth international workshop on seeds: Basic and applied aspects of seed biology. Paris, Association pour la Formation Professionelle de l'lnterprofession Semences.Google Scholar
De Jong, R. and Best, K.F. (1979) The effect of soil water potential, temperature and seeding depth on seedling emergence of wheat. Canadian Journal of Soil Science 59, 259–264.Google Scholar
Dutta, S. and Bradford, K.J. (1994) Water relations of lettuce seed thermoinhibition. II. Ethylene and endosperm effects on base water potential. Seed Science Research 4, 11–18.Google Scholar
Ellis, R.H. and Butcher, P.D. (1988). The effects of priming and natural differences in quality amongst onion seed lots on the response of the rate of germination to temperature and the identification of the characteristics under genotypic control. Journal of Experimental Botany 39, 935–950.Google Scholar
Ellis, R.H., Covell, S., Roberts, E.H. and Summerfield, R.J. (1986) The influence of temperature on seed germination rate in grain legumes. II. Intraspecific variation in chickpea at constant temperature. Journal of Experimental Botany 37, 1503–1515.CrossRefGoogle Scholar
El-Sharkawi, H.M. and Springuel, I. (1977) Germination of some crop plant seeds under reduced water potential. Seed Science and Technology 5, 677–688.Google Scholar
Feddes, R.A. (1972). Effects of water and heat on seedling emergence. Journal of Hydrology 16, 341–359.CrossRefGoogle Scholar
Finch-Savage, W.E. and Phelps, K. (1993) Onion (Allium cepa L.) seedling emergence patterns can be explained by the influence of soil temperature and water potential on seed germination. Journal of Experimental Botany 44, 407–414.CrossRefGoogle Scholar
Fyfield, T.P. and Gregory, P.J. (1989) Effects of temperature and water potential on germination, radicle elongation and emergence of mungbean. Journal of Experimental Botany 40, 667–674.Google Scholar
Garcia-Huidobro, J., Monteith, J.L. and Squire, G.R. (1982) Time, temperature and germination of pearl millet (Pennisetum typhoides, S & H). I. Constant temperature. Journal of Experimental Botany 33, 288–296.Google Scholar
Gummerson, R.J. (1986) The effect of constant temperatures and osmotic potential on the germination of sugar beet. Journal of Experimental Botany 37, 719–741.Google Scholar
Hageseth, G.T. and Cody, A.L. Jr. (1993) Energy-level model for isothermal seed germination. Journal of Experimental Botany 44, 119–125.Google Scholar
Khah, E.M., Ellis, R.H. and Roberts, E.H. (1986) Effects of laboratory germination, soil temperature and moisture content on the emergence of spring wheat. Journal of Agricultural Science (Cambridge) 107, 431–438.CrossRefGoogle Scholar
Karssen, C.M., Haigh, A.M., van der Toorn, P. and Weges, R. (1989) Physiological mechanisms involved in seed priming, pp 269–280 in Taylorson, R. B. (Ed.) Recent advances in the development and germination of seeds. New York, Plenum Press.CrossRefGoogle Scholar
Labouriau, L.G. and Osborn, J.H. (1984). Temperature dependence of the germination of tomato seeds. Journal of Thermal Biology 9, 285–295.CrossRefGoogle Scholar
Lafond, G.P. and Baker, R.J. (1986) Effects of temperature, moisture stress, and seed size on germination of nine spring wheat cultivars. Crop Science 26, 563–567.CrossRefGoogle Scholar
Lindstrom, M.J., Papendick, R.I. and Koehler, F.E. (1976). A model to predict winter wheat emergence as affected by soil temperature, water potential, and depth of planting. Agronomy Journal 68, 137–141.CrossRefGoogle Scholar
McGinnies, W.J. (1960) Effects of moisture stress and temperature on germination of six range grasses. Agronomy Journal 52, 159–162.CrossRefGoogle Scholar
Michel, B.E. (1983) Evaluation of water potential of solutions of polyethylene glycol 8000 both in the absence and presence of other solutes. Plant Physiology 72, 66–70.Google Scholar
Ni, B.R. and Bradford, K.J. (1992) Quantitative models characterizing seed germination responses to abscisic acid and osmoticum. Plant Physiology 98, 1057–1068.CrossRefGoogle ScholarPubMed
Ni, B.R. and Bradford, K.J. (1993) Germination and dormancy of abscisic acid- and gibberellin-deficient mutant tomato (Lycopersicon esculentum) seeds. Sensitivity of germination to abscisic acid, gibberellin, and water potential. Plant Physiology 101, 607–617.Google Scholar
Sharma, M.L. (1976) Interaction of water potential and temperature effects on germination of three semi-arid plant species. Agronomy Journal 68, 390–394.CrossRefGoogle Scholar
Tadmor, N.H., Cohen, Y. and Harpaz, Y. (1969). Interactive effects of temperature and osmotic potential on the germination of range plants. Crop Science 9, 771–773.Google Scholar
Thornley, J.H.M. (1986) A germination model: responses to time and temperature. Journal of Theoretical Biology 123, 481–492.Google Scholar
Welbaum, G.E. and Bradford, K.J. (1991) Water relations of seed development and germination in muskmelon (Cucumis melo L). VI. Influence of priming on germination responses to temperature and water potential during seed development. Journal of Experimental Botany 42, 393–399.Google Scholar