Synergetic action of light and temperature on seed germination of some solanaceae members

The objective of the present study was to evaluate the effects of nine combinations of temperature and light on seeds germination of four solanaceae species (Datura innoxia, Hyoscyamus muticus, Solanum nigrum and Withania somnifera) in germination chamber. The influence of combined of three alternative temperature regimes from 10 to 40 °C, with 10°C intervals, under three light levels (the continuous white light, alternative and darkness) were tested. The germination parameters as germination percentage, seed vigor index, dormancy, germination speed and germination index, and were measured and calculated. The data reveled some similarities in germination percentage and seedling vigor index among Datura innoxia, Solanum nigrum in one hand and between Hyscyamus muticus and Withinia sommenefreae on the other hand, while germination speed and germination index showed some similarities between Datura innoxia, Withinia sommenefreae and between Hyscyamus muticus and Solanum nigrum. The optimum condition for the germination of the seeds was varied with species (species-dependent): some species Hyoscyamus muticus and Withinia sommenefreae germinate easier under combined effects of light and temperature, whereas, Solanum nigrum and Datura innoxia decreased their germination in darkness conditions. The maximal germination was reached in Hyoscyamus muticus follwed by Withania somnifera, Solanum nigrum and Datura innoxia species under wide range of selected combinations. With the exception of Datura innoxia all other species seemed a photoplastic character. No relationship was found between germination percentage and alternating temperature especially in Hyoscyamus muticus and Withania somnifera. Alternating temperature is not the main factor affecting germination percentage. We concluded that the regime of light suppressed the effects alternating temperatures on seed germination of Datura innoxia species. It was concluded that synergized effects of light and alternating temperatures, enhanced seed germination of Hyoscyamus mutucs and Solanum nigrum. Thus, the light regime can play a vital role in present and future weed management strategies.