Hostname: page-component-848d4c4894-jbqgn Total loading time: 0 Render date: 2024-07-02T14:57:50.911Z Has data issue: false hasContentIssue false
  • English
  • Français

Water relations of lettuce seed thermoinhibition. I. Priming and endosperm effects on base water potential

Published online by Cambridge University Press:  19 September 2008

Kent J. Bradford  and
Oscar A. Somasco
Kent J. Bradford*
Affiliation:
Department of Vegetable Crops, University of California, Davis, CA 95616-8631, USA
Oscar A. Somasco
Affiliation:
Department of Vegetable Crops, University of California, Davis, CA 95616-8631, USA
*
* Correspondence
Get access Rights & Permissions [Opens in a new window]

Abstract

Lettuce (Lactuca sativa L.) seeds are inhibited from germinating above an upper temperature limit that is dependent upon cultivar, growing conditions and seed treatments. Thermoinhibition is accompanied by an increasing sensitivity of germination to reduced water potentials (ψ). We have employed a water relations analysis (hydrotime model) of seed germination rates to investigate the basis of thermoinhibition. Germination rates can be characterized by the distribution of base water potentials among seeds in the population (ψb(g)) and a hydrotime constant indicating the total accumulated hydrotime (MPa · h) above the base required for radicle emergence. The hydrotime model adequately described germination time courses across a range of ψ at both high and low temperatures. Increasing temperature caused the ψb(g) distributions to become more positive, accounting for the greater sensitivity to ψ and inhibition of germination. Increases in embryo osmotic potential and in the turgor yield thresholds of both the radicle and the endosperm/pericarp envelope contributed to this change. Seed priming (prehydration and drying) treatments speeded germination by reducing the hydrotime requirement. Priming also resulted in smaller increases in ψb(g) at high temperature, alleviating thermoinhibition by lowering the embryo yield threshold sufficiently to compensate for the increased endosperm resistance. The beneficial effects of priming in lettuce appear to occur primarily in the embryo, rather than in the surrounding envelope tissues.

Keywords

germinationhydrotimeLactuca sativa L.lettuceseed dormancythermoinhibitionwater relations
Type
Research papers
Information
Seed Science Research , Volume 4 , Issue 1 , March 1994 , pp. 1 - 10
Copyright
Copyright © Cambridge University Press 1994

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Borthwick, H.A. and Robbins, W.W. (1928) Lettuce seed and its germination. Hilgardia 3, 275–305.CrossRefGoogle Scholar
Bradford, K.J. (1986) Manipulation of seed water relations via osmotic priming to improve germination under stress conditions. HortScience 21, 1105–1112.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 Galili, G. (Eds) Seed development and germination. New York, Marcel Dekker, Inc.Google 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) Basic and applied aspects of seed biology: Proceedings, Fourth International Workshop on Seeds. Paris, Association pour la Formation Professionelle de l'Interprofession Semences.Google Scholar
Carpita, N.C., Nabors, M.W., Ross, C.W. and Petretic, N.L. (1979a). Growth physics and water relations of red-light-induced germination in lettuce seeds. III. Changes in the osmotic and pressure potential in the embryonic axes of red- and far-red-treated seeds. Planta 144, 217–224.CrossRefGoogle ScholarPubMed
Carpita, N.C., Nabors, M.W., Ross, C.W. and Petretic, N.L. (1979b) Growth physics and water relations of red-light-induced germination in lettuce seeds. IV. Biochemical changes in the axes of red- and far-red-treated seeds. Planta 144, 225–233.CrossRefGoogle ScholarPubMed
Dahal, P. and Bradford, K.J. (1990) Effects of priming and endosperm integrity on seed 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 Haigh, A.M. (1993) The concept of hydrothermal time in seed germination and priming. pp 1009–1014 in Côme, D. and Corbineau, F. (Eds) Basic and applied aspects of seed biology: Proceedings, Fourth International Workshop on Seeds. Paris, Association pour la Formation Professionelle de l'Interprofession Semences.Google Scholar
Drew, R.K.L. and Brocklehurst, P.A. (1984) Investigations on the control of lettuce seed germination at high temperatures. Journal of Experimental Botany 35, 986–993.CrossRefGoogle Scholar
Drew, R.K.L. and Brocklehurst, P.A. (1990) Effects of temperature of mother-plant environment on yield and germination of seeds of lettuce (Lactuca sativa). Annals of Botany 66, 63–71.CrossRefGoogle Scholar
Dunlap, J.R., Scully, B.T. and Reyes, D.M. (1990) Seed coat-mediation of lettuce germination responses to heat and sodium chloride. Journal of the Rio Grande Valley Horticultural Society 43, 55–61.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.CrossRefGoogle Scholar
Georghiou, K., Psaras, G. and Mitrakos, K. (1983) Lettuce endosperm structural changes during germination under different light, temperature, and hydration conditions. Botanical Gazette 144, 207–211.Google Scholar
Gordon, A.G. (1973) The rate of germination. pp 391–409 in Heydecker, W. (Ed.) Seed ecology. London, Butter-worths.Google Scholar
Groot, S.P. and Karssen, C.M. (1992) Dormancy and germination of abscisic acid-deficient tomato seeds. Studies with the sitiens mutant. Plant Physiology 99, 952–958.CrossRefGoogle ScholarPubMed
Guedes, A.C. and Cantliffe, D.J. (1980) Germination of lettuce seeds at high temperature after seed priming. Journal of the American Society for Horticultural Science 105, 777–781.CrossRefGoogle Scholar
Gummerson, R.J. (1986) The effect of constant temperatures and osmotic potential on the germination of sugar beet. Journal of Experimental Botany 37, 729–741.Google Scholar
Haigh, A.H. (1988) Why do tomato seeds prime? Physiological investigations into the control of tomato seed germination and priming. PhD Dissertation. Macquarie University, Sydney, Australia.Google Scholar
Ikuma, H. and Thimann, K.V. (1963) The role of the seed-coats in germination of photosensitive lettuce seeds. Plant and Cell Physiology 4, 169–185.Google Scholar
Karssen, C.M., Haigh, A., 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
Khan, A.A. (1992) Preplant physiological seed conditioning. Horticultural Reviews 14, 131–181.CrossRefGoogle Scholar
Michel, B.E. (1983) Evaluation of the water potentials of solutions of polyethylene glycol 8000 both in the absence and presence of other solutes. Plant Physiology 72, 66–70.Google Scholar
Nabors, M.W. and Lang. A. (1971) The growth physics and water relations of red-light-induced germination in lettuce seeds. I. Embryos germinating in osmoticum. Planta 101, 1–25.CrossRefGoogle ScholarPubMed
Ni, B.R. and Bradford, K.J. (1992) Quantitative models characterizing seed germination responses to abscisic acid and osmoticum. Plant Physiology 98, 1057–1068.Google Scholar
Ni, B.R. and Bradford, K.J. (1993) Germination and dormancy of abscisic acid- and gibberellin-deficient mutant tomato seeds. Sensitivity of germination to abscisic acid, gibberellin, and water potential. Plant Physiology 101, 607–617.Google Scholar
Prusinski, J. and Khan, A.A. (1990) Relationship of ethylene production to stress alleviation in seeds of lettuce cultivars. Journal of the American Society for Horticultural Science 115, 294–298.Google Scholar
Takeba, G. (1980a) Accumulation of free amino acids in the tips of non-thermodormant embryonic axes accounts for the increase in growth potential of New York lettuce seeds. Plant and Cell Physiology 21, 1639–1644.CrossRefGoogle ScholarPubMed
Takeba, G. (1980b) Effects of temperature, red light and hormones on the accumulation of free amino acids in osmotically growth-inhibited embryonic axes of New York lettuce seeds. Plant and Cell Physiology 21, 1645–1649.CrossRefGoogle ScholarPubMed
Valdes, V.M., Bradford, K.J. and Mayberry, K.S. (1985) Alleviation of thermodormancy in coated lettuce seeds by seed priming. HortScience 20, 1112–1114.CrossRefGoogle Scholar
Valdes, V.M. and Bradford, K.J. (1987) Effects of seed coating and osmotic priming on the germination of lettuce seeds. Journal of the American Society for Horticultural Science 112, 153–156.CrossRefGoogle Scholar
Weges, R. (1987) Physiological analysis of methods to relieve dormancy of lettuce seeds. PhD Dissertation. Agricultural University, Wageningen, The Netherlands.Google Scholar
Weges, R., Koot-Gronsveld, E. and Karssen, C.M. (1991) Priming relieves dormancy in lettuce seeds independently of changes in osmotic constituents. Physiologia Plantarum 81, 527–533.CrossRefGoogle Scholar
Wurr, D.C.E., Fellows, J.R. and Drew, R.K.L. (1987) The germination and the forces required to penetrate seed layers of different seedlots of three cultivars of crisp lettuce. Annals of Applied Biology 110, 405–411.CrossRefGoogle Scholar