Influence of temperature on seed germination and the nutritional requirements for embryo growth in Arum maculatum L.

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SUMMARY

The temperature requirements for seed germination and nutritional requirements for embryo growth were investigated in seed populations of Arum maculatum L. plants growing in South-east England. Seeds freshly harvested from orange-red berries were shown to require a protracted period of chilling at about 6 °C for germination to occur in either the light (12 h photoperiod) or the dark. There was no obligate requirement for chilled seeds to be transferred to higher temperatures for germination to occur, although such treatment did facilitate germination. Germination rate at cold temperature varied over three consecutive harvest years with faster germination rates apparently related to warmer temperature during seed development on the parent plant. This positive effect of warm temperature pretreatment on cold temperature germination rate was also evident in harvested seeds. Depending on the initial level of seed dormancy, the effect could be saturated after only a few weeks at 25 °C. The observation that similar germination rates occurred in seed which had been incubated in the light or dark for up to 1 yr at 11–28 °C indicated that such treatments neither altered seed viability nor induced secondary dormancy. Whereas extensive periods of time at low temperatures are a prerequisite for seed germination, isolated embryos were capable of development in vitro without chilling, even on a minimal medium of KNO3 and sucrose only, but not on water or KNO3 alone. In vitro seedling development progressed optimally through tuber formation to first leaf production within 9 months. It is concluded that the seed dormancy mechanism in this spring geophyte serves to facilitate germination after the winter. Furthermore, the ability to retain viability in the hydrated state suggests that seeds which remain dormant after the first winter are physiologically capable of surviving the first summer and germinating after the second winter.

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