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Arabidopsis > Protocols > Germination assays > Seed priming
Arabidopsis | Sugar Beet | Intranet

Seed priming

Seed priming

I. Introduction

Seed priming (pre-sowing imbibition treatment) is widely used to enhance seed performance with respect to rate and uniformity of germination (Heydecker et al., 1973; Hegarty, 1978; Heydecker, 1978; for a review see Bradford, 1986). These treatments are based upon controlled hydration of the seeds; during priming, seeds are brought up to, and eventually held at, the end of phase II of water uptake of the germination process without entering the initial growth phase characterized by radicle protrusion through the seed coat. Since most embryos of seeds are desiccation tolerant up to this developmental stage, the advancement of the seeds in the germination process during priming can be arrested by drying.

Several methods have been described to prime seeds. For osmopriming, controlled water uptake by the seeds is achieved by the use of an inert osmoticum such as polyethylene glycol (PEG) (see Bradford, 1986). There are other priming techniques in which controlled hydration of the seeds is effected with a water-absorbing carrier as in solid matrix priming (Taylor et al., 1988), with pure water as in hydropriming (Tarquis and Bradford, 1992; Job et al., 1997) or with only water vapor as in drum priming (Rowse, 1996).

A major difficulty encountered in seed priming, particularly with the hydropriming and drum priming techniques, is to control seed imbibition to a level permitting pregerminative processes to proceed without reaching the stage of radicle emergence where seeds become desiccation intolerant. The consequence of drying back intolerant primed seeds for storage purposes can be a total loss of the treated batch.

Besides providing added-value to the seeds commercialized by seed companies in developed countries, seed priming has also been optimized to increase crop establishment in developing countries, which is a major concern in these countries. In the latter case, the seed imbibition protocol is referred to as “on-farm seed priming”, and proved to be quite robust and efficient provided farmers can prime their own seed if they know the safe limits, see http://www.seedpriming.org.


II. Experimental Seed Priming Protocols

We have set up different priming protocols, either for sugarbeet or Arabidopsis seeds, which can be easily carried out in the laboratory.
Sugarbeet (Beta vulgaris L.) seeds can be primed as follows:

(1) Hydropriming pre-treatment. This pre-treatment includes the three following steps (Job et al., 1997):
  • a washing step of the seeds [4 hours in milli-Q water (Millipore) at 20°C] to remove germination inhibitors from the seed coats, followed by re-drying in air at approx. 20°C for 12h to the initial moisture content (8.45% on a dry weight basis);
  • a controlled hydration of the washed seeds at various temperatures ranging from 5 to 36°C (± 1°C) for various durations up to 5 d; and
  • a dehydration of the treated seeds to the initial moisture content as described above.
Controlled hydration is achieved by placing 2.5 g of seeds (on a fresh weight basis) on filter paper (0.82 g) moistened with a calculated amount of milli-Q water (0.81 ml) in plastic tubes (h = 7 cm; d = 3 cm) sealed with airtight closures. Then, the tubes containing the seeds are slowly agitated in a chamber at the desired temperature in the dark. Following incubation, seeds are weighed to calculate their water uptake (under these conditions seed fresh weight increased by 30 ± 1%) and then are re-dried at room temperature as described above. None of the seeds germinate by 5 d of incubation.
Job C, Kersulec A, Ravasio L, Chareyre S, Pépin R, Job D (1997) The solubilization of the basic subunit of sugarbeet seed 11-S globulin during priming and early germination. Seed Science Research 7, 225–243.

(2) Osmotic pre-treatment
Seeds are placed on a layer of cotton wool imbibed with a solution of PEG-8000 at –2.0 MPa for various durations up to 14 d at 25°C, or for 2 and 7 d at various temperatures ranging from 5 to 35°C (± 0.5°C). The concentration of the PEG solution is calculated for each temperature according to Michel and Kaufmann (1973). Following incubation, treated seeds are rinsed and dried to their original moisture content (Michel & Kaufmann, 1973).

Effects of duration of hydropriming (●) and osmopriming (○) at 25°C in air on germination characteristics of primed seeds (Capron et al, 2000)
(A) Times to obtain 50% germination (t50) at 5°C.
(B) Germination percentages obtained after 10 d at 10°C (G10) ± SD.

For an application of these treatments to Arabidopsis seeds, see:
Gallardo K, Job C, Groot SPC, Puype M, Demol H, Vandekerckhove J, Job D (2001) Proteomic analysis of Arabidopsis seed germination and priming. Plant Physiology 126, 835-848.

References


Bradford KJ (1986) Manipulation of seed water relations via osmotic priming to improve germination under stress conditions. HortScience 21, 1105–1112.

Capron I, Corbineau F, Dacher F, Job C, Côme D, Job D (2000) Sugarbeet seed priming: effects of priming conditions on germination, solubilization of 11-S globulin and accumulation of LEA proteins. Seed Science Research 10, 243-254

Hegarty TW (1978) The physiology of seed hydration and dehydration, and the relation between water stress and the control of germination: a review. Plant, Cell and Environment 1, 101–119.

Heydecker W (1978) “Primed” seeds for better crop establishment? Span 21, 12–14.

Heydecker W, Higgins J, Gulliver RL (1973) Accelerated germination by osmotic seed treatment. Nature 246, 42–44.

Job C, Kersulec A, Ravasio L, Chareyre S, Pépin R, Job D (1997) The solubilization of the basic subunit of sugarbeet seed 11-S globulin during priming and early germination. Seed Science Research 7, 225–243.

Michel BE, Kaufmann MR (1973) The osmotic potential of polyethylene glycol 6000. Plant Physiology 51, 914–916.

Rowse HR (1996) Drum priming – a non-osmotic method of priming seeds. Seed Science and Technology 24, 281–294.

Tarquis AM, Bradford KJ (1992) Prehydration and priming treatments that advance germination also increase the rate of deterioration of lettuce seeds. Journal of Experimental Botany 43, 307–317.

Taylor AG, Klein DE, Whitlow TH (1988) SMP: solid matrix priming. Scientia Horticulturae 37, 1–11.
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