Jiří PAZDERA

Czech University of Agriculture in Prague, Faculty of Agronomy, 165 21 Prague 6 - Suchdol, Czech Repuplic (contact e-mail: pazdera@af.czu.cz)

Introduction

The seed hydration treatment is an interesting way for improvement of seed quality before sowing. The principle of hydration treatments uses the fact that it is possible to hydrate seeds in some ways at a moisture level sufficient to initiate the early events of germination but not sufficient to permit radicle protrusion.Seeds are hydrated by the various methods for improving of seed performance after sowing. These methods increase uniformity and speed of germination and by this way can to contribute to faster and uniform emergence, especially in sub-optimal environmental conditions (Copeland and McDonald, 1995).

Methods of hydration can be divided into two groups depending on whether water uptake is non-controlled (prehydration) or controlled (osmotic priming, solid matrix priming) (Taylor et al., 1998).

Water uptake at prehydration is governed only by affinity of the seed tissue for water. Seeds are imbibed on moistened blotters or soaking in water. Because water is not limited, seeds can eventually germinate, assuming that seeds are viable, not dormant and optimal conditions are supplied. Therefore, in non-controlled systems the process must be arrested at a specific time to prevent radicle protrusion.

In controlled hydration the amount of water available for seed is restricted or water potential of hydration environment can be regulated. Seeds are imbibed at osmotic priming in solution of osmotica, for example KNO3, K3PO4, glycerol, mannitol, polyethyleneglycol - PEG. The solid matrix priming employs as hydration environment a mixture of solid carrier (vermiculite, Celite, Mikro-Cel) with water.

After hydration, seeds are dried back to enable normal handling, storage and planting. But drying can reduce advantages gained by hydration. Various methods of drying are used: drying open on filter paper by ambient air or drying in oven with ambient or forced air.

Material and methods

This experiment was done with standard seed lots of carrot and onion, three cultivars of each kind, appointed for commercial use.

Seed lots were treated by two hydration methods: prehydration and osmotic priming (for details see Table 1). Prehydration was realized in distilled water, without aeration, at temperature 20^oC. Osmotic priming was done in PEG 6000 solution at 20^oC, prepared according to Michel and Kaufmann (1973). The PEG solution was aerated by ambient air. After both hydration methods seed were dehydrated back on filter paper in two steps: at first free water was quickly drained off and then seed were let open for 24 hours on filter paper at room temperature 22^oC and relative humidity (RH) 42%.

Table 1. Variants of seed treatment

Germination percentage was counted each day per 24 hours and total germination percentage, mean time of germination (MTG) and germination energy of all treated samples and the non-treated control were counted after testing. Seeds with radicle protrusion of 3 mm were scored as germinating seeds. Mean time of germination (MTG) was calculated from daily germination values by equation of Nichols and Heydecker (1968) and germination energy was calculated as cumulative germination after 3 days.

Experimental data were analysed with statistical packet SAS, version 6.12. (SAS Institute, Inc. Cary, NC USA). Analysis of variance was used for evaluation, exactly SAS GLM (General Linear Model) procedure. Means were compared by Tukey`s test.

Results and discussion

Onion
All three seed lots after prehydration treatment reached higher germination percentage than non-treated control samples and their MTG were shorter in comparison with control (data is not showed).

The prehydration with duration 6 hours was the best variant of treatment in average of all samples with the highest germination percentage, germination energy and the shortest MTG. The germination percentage and germination energy after prehydration treatments 3 and 6 hours were significantly highest than control, but decrease of MTG after these treatments was not significant in comparison with control (Table 2).

Table 2. Onion - differences between treated samples and non-treated control (average of three seed lots)

Values in columns marked by the same letter are not significantly different (P<0.05)

Carrot
The germination percentage of all three samples after treatment stayed on the same level as non-treated control, differences were non-significant. MTG after treatment decreased in comparison with control, significantly in all variants of treatment.

Any significant differences in germination percentage between treated samples and control were not register, thought germination percentage after some variants of treatment increased (in average of all seed lots). The germination energy (in average) after all variants of treatment increased significantly too. The mean time of germination in average was the shortest after priming treatment with osmotic potential -1.0 MPa and with duration 12 and 15 hours (Table 3).

Table 3. Carrot - differences between treated samples and non-treated control (average of three seed lots)

Conclusion

The seed hydration treatment increase uniformity and speed of germination of treated seed lots and by this way can to contribute to faster and uniform emergence for improving of the crop stand uniformity. The effect of this treatment depends on used method and duration of the treatment.

References

1. Copeland, L. O., McDonald, M. B. (1995). Principles of Seed Science and Technology. Chapman a Hall, New York., 409 s.

2. Michel, B. E., Kaufmann, M. R. (1973). The osmotic potential of polyethylene glycol 6000. Plant Physiology 51: 914 - 916.

3. Nichols, M. A., Heydecker, W. Two approaches to the study of germination data. Proceeding of the International Seed Testing Association, 33, 1968: 531 -540.

4. Taylor, A. G., Allen, P. S., Bennett, M. A., Bradford, K. J., Burris, J. S., Misra, M. K. (1998). Seed enhancements. Seed Sci. Res. 8: 245 - 256.

5. This research was supported by Grant Agency of the Czech Republic within the scope of project No. 521/02/D171