INFLUENCE OF TEMPERATURE ON SEED-GERMINATION AND THE NUTRITIONAL-REQUIREMENTS FOR EMBRYO GROWTH IN ARUM-MACULATUM L

The temperature requirements for seed germination and nutritional requ irements for embryo growth were investigated in seed populations of Ar um maculatum L. plants growing in South-east England. Seeds freshly ha rvested from orange-red berries were shown to require a protracted per iod of chilling at about 6-degrees-C for germination to occur in eithe r the light (1 2 h photoperiod) or the dark. There was no obligate req uirement for chilled seeds to be transferred to higher temperatures fo r germination to occur, although such treatment did facilitate germina tion. Germination rate at cold temperature varied over three consecuti ve harvest years with faster germination rates apparently related to w armer temperature during seed development on the parent plant. This po sitive effect of warm temperature pretreatment on cold temperature ger mination rate was also evident in harvested seeds. Depending on the in itial level of seed dormancy, the effect could be saturated after only a few weeks at 25-degrees-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-degrees-C indicated that such treatments neith er altered seed viability nor induced secondary dormancy. Whereas exte nsive periods of time at low temperatures are a prerequisite for seed germination, isolated embryos were capable of development in vitro wit hout chilling, even on a minimal medium of KNO3 and sucrose only, but not on water or KNO3 alone. In vitro seedling development progressed o ptimally through tuber formation to first leaf production within 9 mon ths. It is concluded that the seed dormancy mechanism in this spring g eophyte 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.