Abstract
BackgroundLight and temperatures of germination greatly affect germination of several Cucurbitaceae species. Environmental conditions prevailing at seed maturation time can affect dormancy and germination requirements. Citrullus colocynthis seeds have a deep dormancy. This perennial prostrate shrub grows all over the year in the arid Arabian deserts. We explored if seed dormancy and germination requirements of C. colocynthis depend on time of fruit collection. Matured seeds were collected at five different times during 2014/2015 year from a population around Dubai city. Fresh seeds were germinated at three temperature regimes in both continuous darkness and alternating 12 h light/12 h darkness. Impacts of seed storage and other treatments on germination were applied on seeds collected in March and exhibited deep dormancy.ResultsMarch collected seeds almost did not germinate in both light and dark at the three temperatures, but those of the other collections responded differently to both light and temperatures. At the lowest temperatures, seeds of all collections did not germinate in light, but those of June, October and December collections germinated in dark. There were negative correlations between final germination and seed length, width, mass and coat thickness. Physical scarification, water soaking and seed storage did not break dormancy of March collection.ConclusionsGermination of C. colocynthis is very sensitive to light and incubation temperature as well as to the environmental conditions associated with the time of seed maturation. It is important to investigate the effects of environmental factors prevailing during seed maturation under controlled conditions to understand exact reasons for unusual seed dormancy and germination requirements of C. colocynthis, which seems to be very sensitive to maternal environment.
Highlights
Light and temperatures of germination greatly affect germination of several Cucurbitaceae species
For December collection, germination reached almost 100% at the highest temperature in light, but at lowest temperature in dark. These results indicate that germination in light requires higher temperatures, but germination in darkness seems to be independent on temperature regime; it depends more on the time of seed collection (Fig. 1)
The present study showed that C. colocynthis seeds germinated very well in both light and dark at moderate and higher temperatures (20/30 and 25/35 °C)
Summary
Light and temperatures of germination greatly affect germination of several Cucurbitaceae species. Environmental conditions prevailing at seed maturation time can affect dormancy and germination requirements. Citrullus colocynthis seeds have a deep dormancy. This perennial prostrate shrub grows all over the year in the arid Arabian deserts. We explored if seed dormancy and germination requirements of C. colocynthis depend on time of fruit collection. Fresh seeds were germinated at three temperature regimes in both continuous darkness and alternating 12 h light/12 h darkness. Seed dormancy is a temporary failure of a viable seed to complete germination under normally favorable physical environmental conditions [1]. Several studies have reported that autumn or winter-matured seeds germinated significantly greater at higher temperatures and in continuous light, compared to spring- or summer-matured seeds [12, 14,15,16]. The seasonal timing of seed maturation and dispersal can in turn determine the season of seed germination and germination rate and the overall life history [14]
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