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Germination response to environmental factors often depends on the seed source. Habitat-indifferent halophytes that can grow well under both saline (SH) and non-saline habitats (NSH) offer a good opportunity to understand salinity tolerance during the germination stage under varying environmental factors, such as temperature and light. This study compared seed germination responses among different populations of two common habitat-indifferent halophytes (Salsola drummondii and Suaeda vermiculata) from subtropical hyperarid deserts of the United Arab Emirates (UAE) and semiarid warm sub-tropical areas in Pakistan. This study highlights many similarities and differences in the seed germination and recovery responses of habitat-indifferent halophytes occurring in two contrasting climatic regions. The germination window of UAE seeds was wider, i.e., they germinated at higher rates under all temperatures in both light and darkness. This indicates that seeds of UAE populations can germinate at any time of the year, if conditions are optimal, and faciltate a faster seedling establishment under fluctuating harsh environmental conditions compared to populations from semiarid warm sub-tropical areas in Pakistan. The eco-physiological significance of the responses is also discussed.

Background This is the first study on seed germination of Cucumis prophetarum in the Arabian Peninsula. Light and temperature as the main environmental factors and seed storage conditions greatly affect the germination of many Cucurbitaceae species. C. prophetarum is the perennial prostrate with woody rootstocks that grow throughout the year in the arid Arabian deserts. We examined the effects of seed storage conditions and sterilization by sodium hypochlorite (NaOCL) on germination of C. prophetarum seeds. Matured, fresh and field stored seeds were collected in March of 2016 and 2017 from a population in the United Arab Emirates. Fresh and the stored seeds (field, freeze, and room temperature) were germinated at three temperature regimes (15/25, 20/30 and 25/35°C) in both continuous darkness and alternating 12 h light/12 h darkness. Results The fresh and freeze stored seeds had higher germination percentage than the field and room temperature stored seeds. High germination was recorded in both lower and moderate temperatures (15/25 and 20/30°C) in light conditions. Sterilization of the seeds by NaOCl had a negative effect on the speed and germination percentage under all storage conditions, and it changes light and temperature requirements of seeds for germination. Conclusions Germination of C. prophetarum is sensitive to incubation light and temperature as well as to the seed storage conditions. The germination ability of stored seeds indicates that seed storage behaviour of C. prophetarum is orthodox. Light and temperature requirements for seed germination reflects a suitable place, habitat, and time for seedling emergence of C. prophetarum. The effect of NaOCl treatment on the germination may be associated with concentration and exposure periods of seeds. Therefore, we suggest that when using NaOCl for seed sterilization or to stimulate the germination, caution must be taken for using its concentration and exposure time, especially for species with thin and soft seed coats like C. prophetarum. Further studies on seed germination ecology would help to understand better the adaptive strategy of the C. prophetarum in the arid desert environments.