Factors influencing the storability of Fagus sylvatica L. seeds after release from dormancy

Stanislawa Pukacka,Ewelina Ratajczak

doi:10.1007/s10725-013-9832-5

Stanislawa Pukacka, Ewelina Ratajczak

Open Access

https://doi.org/10.1007/s10725-013-9832-5

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Abstract

Seeds of beech (Fagus sylvatica L.) that have been subjected to dormancy breaking consisting of 10 weeks of prechilling at 3 °C and 34 % water content (WC) and then desiccation to 10 % WC, are non-dormant (ND). ND seeds are characterised by greater sensitivity to storage conditions, than no prechilled, dormant (D) seeds. The aim of the present work was to investigate factors affecting the loss of seed viability during storage of D and ND beech seeds at different temperatures (4 and 20 °C) and humidity levels (45 and 75 % RH) for 3 weeks. In general, both D and ND seeds maintained a high germination capacity after storage at 4 °C. At 20 °C and 45 and 75 % RH the germination capacity of D seeds diminished to 80 and 28 %, respectively. Under the same conditions, ND seeds lost germination capacity to a greater degree, with only 62 and 7 % germinated seeds, respectively. At 20 °C, an increase in production of reactive oxygen species was observed, and the increase was significantly higher in ND seeds. The loss of germination capacity was coincident with an increase in electrolyte leakage and accumulation of free fatty acids, which suggests that membrane deterioration was the cause of the decline in germinability. ND seeds stored at 20 °C and 45 and 75 % RH showed a greater decrease than D seeds in contents of the primary phospholipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE) as well as in polyunsaturated fatty acids (18:2 and 18:3). ND seeds possessed more unsaturated fatty acids, especially 18:3, than D seeds in the phospholipid fraction before storage. D seeds were characterised by a significantly higher level of α-tocopherol and UV-absorbing phenols. The level of ascorbate was similar in D and ND seeds. D seeds contained glutathione in both reduced (GSH) and oxidised (GSSG) forms, and GSSG dominated GSH. ND seeds contained more GSSG form than D seeds. We concluded that the membranes of ND seeds are exposed to greater oxidative stress during storage due to higher levels of unsaturation and lower levels of α-tocopherol, the main antioxidant that protects membranes against free radical attack.

Highlights

The process of seed germination is strongly affected by environmental factors, which can significantly alter the rate and success of germination
The loss of germination capacity was coincident with an increase in electrolyte leakage and accumulation of free fatty acids, which suggests that membrane deterioration was the cause of the decline in germinability
After release from dormancy and drying to 10 % water content (WC), ND seeds contained a slightly greater amount of ascorbic acid (ASA) and DHA in embryonic axes compared to D seeds

Summary

Introduction

The process of seed germination is strongly affected by environmental factors, which can significantly alter the rate and success of germination. Cold stratification is a method routinely utilised to maximise the germination potential of seeds (Yamauchi et al 2004; Narsai et al 2011). Seeds of woody plants are characterised by a deep dormancy, and it is often difficult to obtain a high percentage of seedlings from these seeds in nurseries. In temperate climates, spring often brings drought in combination with high temperatures, which can disturb the process of breaking dormancy. One method that leads to a high percentage of germination in nurseries, recommended for beech and seeds of other species by Suszka et al (1996), is special preparation before sowing under conditions, particular to each type of seeds, that break dormancy, but hinders radicle protrusion.

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