Document Type : Original Article

Authors

1 Department of Agricultural Sciences, Payame Noor University, Tehran, Iran

2 Department of Agronomy, Gorgan Agricultural Sciences and Natural Sciences Research Center, Gorgan

3 Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources

4 ...........

Abstract

This study was evaluated the ability of a hydrothermal time model (HTT) to describe the kinetics of seed germination in crops and also to determine the cardinal temperatures for germination (as a case study; velvetleaf). For this purpose, the experiment was carried out at eight constant temperature regimes (T; 15, 20, 25, 30, 35, 37, 40 and 42°C) at each of the following water potential (ψs; 0, –0.18, –0.36, –0.54 and –0.72 MPa; using PEG 6000). The results indicated that ψ influenced germination rate and germination percentage (P < 0.0001). For this seed lot, cardinal temperatures were 11.8°C for Tb, 35.4°C for To and 45.2°C for Tc in the control (0 MPa) treatment. There was a decrease in hydrotime constant (θH) when T was increased to To and then remained constant at supra-optimal Ts (24 MPa h-1). At the Ts above To, ψb(50) values increased linearly with T. The kT value (the slope of the relationship between ψb(50) and T exceeds To) of this seed lot was calculated as 0.1011 MPa°Ch-1. Moreover, the ψb(50) was estimated to be –0.91 MPa based on this model. Our results show that when the HTT model is applied, it can accurately describe germination response of velvetleaf around Ts and ψs.

Keywords

Allen, P. 2003.When and how many? Hydrothermal models and the prediction of seed germination. New Phytol. 158: 1-3.
Alvarado, V., and K. Bradford. 2002. A hydrothermal time model explains the cardinal temperatures for seed germination. Plant Cell Environ. 25: 1061-1069.
Atashi, S., E. Bakhshandeh., M. Mehdipour., M. Jamali, and J.A. Teixeira da Silva. 2015. Application of a hydrothermal time seed germination model using the Weibull distribution to describe base water potential in zucchini (Cucurbita pepo L.). J. Plant Growth Regul. 34: 150-157.
Atashi, S., E. Bakhshandeh., Z. Zeinali., E. Yassari, and J.A. Teixeira da Silva. 2014. Modeling seed germination in Melisa officinalis L. in response to temperature and water potential. Acta Physiol. Plantarum. 36: 605-611.
Bakhshandeh, E., and M. Gholamhossieni. 2018. Quantification of soybean seed germination response to seed deterioration under PEG-induced water stress using hydrotime concept. Acta Physiol. Plantarum. 40:126.
Bakhshandeh, E., M.Jamali, E. Afshon, and M. Gholamhossieni. 2017. Using hydrothermal time concept to describe sesame (Sesamum indicum L.) seed germination response to temperature and water potential. Acta Physiol. Plantarum. 39:1-9.
Bakhshandeh, E., S. Atashi., M. Hafez-Nia, and H. Pirdashti. 2013. Quantification of the response of germination rate to temperature in sesame (Sesamum indicum). Seed Sci. Technol. 41: 469-473.
Bakhshandeh, E., S. Atashi., M. Hafez-Nia., H. Pirdashti, and J.A. Teixeira da Silva. 2015. Hydrothermal time analysis of watermelon (Citrullus vulgaris cv.‘Crimson sweet’) seed germination. Acta Physiol Plantarum. 37: 1-8.
Baskin, C.C., and J.M. Baskin. 2014. Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, San Diego.
Bewley, J.D., K. Bradford, and H. Hilhorst. 2013. Seeds: physiology of development, germination and dormancy. 3rd edn. Springer, New York.
Bradford, K.J. 1990. A water relations analysis of seed germination rates. Plant Physiol. 94: 840-849.
Bradford, K.J. 1995. Water relations in seed germination. Seed Dev. Germ. 1: 351-396.
Bradford, K.J. 2002. Applications of hydrothermal time to quantifying and modeling seed germination and dormancy. Weed Sci. 50: 248-260.
Bradford, K.J., and D.W. Still. 2004. Applications of hydrotime analysis in seed testing. Seed Technol. 26: 75-85.
Dahal, P., and K.J. Bradford. 1990. Effects of priming and endosperm integrity on seed germination rates of tomato genotypes II. Germination at reduced water potential. J. Exp. Bot. 41: 1441-1453.
Dahal, P., and K.J. Bradford. 1994. Hydrothermal time analysis of tomato seed germination at suboptimal temperature and reduced water potential. Seed Sci. Res. 4: 71-80.
Derakhshan, A., and J. Gherekhloo. 2015. Comparison of hydrothermal time models to seed germination modeling of Phalaris minor on the basis of Normal, Weibull and Gumbel distributions. (In Persian, with English Abstract) J. Plant Prod. Res. 22: 39-57.
García, A.L., J. Recasens.,  F. Forcella., J. Torra, and A. Royo-Esnal. 2013. Hydrothermal emergence model for ripgut brome (Bromus diandrus). Weed Sci. 61: 146-153.
Gummerson, R. 1986. The effect of constant temperatures and osmotic potentials on the germination of sugar beet. J. Exp. Bot. 37: 729-741.
Kebreab, E., and A. Murdoch. 1999. Modelling the effects of water stress and temperature on germination rate of Orobanche aegyptiaca seeds. J. Exp. Bot. 50: 655-664.
Mesgaran, M., H. Mashhadi., H. Alizadeh., J. Hunt., K. Young, and R. Cousens. 2013. Importance of distribution function selection for hydrothermal time models of seed germination. Weed Res. 53: 89-101.
Michel, B.E., and M.R. Kaufmann. 1973. The osmotic potential of polyethylene glycol 6000. Plant Physiol. 51: 914-916.
Rowse, H., and W.E. FinchSavage. 2003. Hydrothermal threshold models can describe the germination response of carrot (Daucus carota) and onion (Allium cepa) seed populations across both sub‐and supra‐optimal temperatures. New Phytol. 158: 101-108.
Sadeghloo, A., J. Asghari, and F. Ghaderi-Far. 2013. Seed germination and seedling emergence of velvetleaf (Abutilon theophrasti) and barnyardgrass (Echinochloa crus-galli). Planta Daninha. 31: 259-266.
Wang, R. 2005. Modeling seed germination and seedling emergence in winterfat (Krascheninnikovia lanata (Pursh) ADJ Meeuse & Smit): Physiological mechanisms and ecological relevance. PhD thesis, University of Saskatchewan.
Watt, M.S., M. Bloomberg, and W.E. FinchSavage. 2011. Development of a hydrothermal time model that accurately characterises how thermoinhibition regulates seed germination. Plant Cell Environ.  34: 870-876.
Watt, M.S., V. Xu, and M. Bloomberg. 2010. Development of a hydrothermal time seed germination model which uses the Weibull distribution to describe base water potential. Ecol. Model. 221: 1267-1272.
Zhang, H., L. Irving., Y. Tian, and D. Zhou. 2012. Influence of salinity and temperature on seed germination rate and the hydrotime model parameters for the halophyte, Chloris virgata, and the glycophyte, Digitaria sanguinalis. South Afr. J. Bot. 78: 203-210.