The effects of time of seed production on the germination response of Spergularia marina

Germination studies were carried out with seeds of Spergularia marina L. Griseb produced over an interval of six months (June‐November). The response of the seeds to light and dark, various constant and alternating temperature regimes, and salinity were determined. In addition, the effects of soil moisture status at the time of seed production on the subsequent germination response of seeds were also determined. Light was an absolute requirement for germination. While a constant temperature regime did not generally favour germination of seed of any month, alternating temperature greatly enhanced germination with an optimum at 5/15°C in all seeds. When imbibed in solutions of different salinities, seeds collected in July and October behaved like true halophyte seeds whereas those collected in June. August, September and November behaved like glycophyte seeds. High concentration of gibberellic acid (3 000 μM) stimulated dark germination in the June and November seed lots, but in light, low GA3 concentration (300 μM) stimulated germination most. The addition of kinetin (30 μM) plus gibberellic acid enhanced germination in the dark in contrast to GA3 alone; kinetin alone stimulated a very low percentage germination. The moisture status of the soil at the time seeds were produced did not affect the germination response of an early seed crop (July) but affected that of the later seeds (August). Judging from the different germination responses, it appears that the seeds belong to at least two physiological groups, one which appears to need either a dark‐wet or cold‐wet pretreatmem for high germination to occur; and the other group which does not need pretreatmem. The ecological significance of these varied responses is discussed in relation to the survival of the species in its habitat.