Habitat-indifferent species that can grow well in both saline and non-saline soils offer a good opportunity for studying seed dormancy and salt tolerance during germination. Here, we assess interactive effects of maternal habitat and incubation conditions on salt tolerance during germination of the habitat-indifferent halophyte Suaeda vermiculata, a common perennial shrub of the arid Arabian deserts. Seeds collected from saline and non-saline habitats were germinated at six salinity levels (0–500 mM NaCl) and incubated at three temperatures and under two light regimes. Studied germination attributes were final germination, germination rate index (GRI) and germination recovery of non-germinated seeds when transferred to distilled water. The results showed insignificant difference in salt tolerance between seeds of the two habitat types at the lower salinities. At higher salinities (400 and 500 mM NaCl), germination of the saline habitat seeds was almost inhibited, but that of non-saline habitat seeds reached various levels depending on light and temperature. Both higher temperatures and darkness resulted in significant reductions of the final germination at the higher salinities. Seeds of the two habitats that did not germinate in the different treatments recovered their germination when transferred to distilled water, indicating that these seeds maintained their viability in saline solution and were able germinate upon the arrival of suitable conditions. Seeds of the two habitats germinated within 2 days at the lower salinities and GRI decreased with the increase in salinity level. Such reduction was obvious for seeds of the saline habitat. Recovery was faster for seeds of the saline habitats, especially for those incubated at higher salinities and in the dark. The difference in dormancy and germination attributes of seeds of the two habitat types reflects ecological adaptations for survival in salt marshes of arid deserts.

Impermeability of the testa hinders efficient penetration of some small chemicals, such as transcriptional inhibitors, through the endosperm and the embryo during seed experiments. In Arabidopsis seeds, 5-bromo-4-chloro-3-indolyl β-d-glucuronic acid, a substrate for β-glucuronidase, did not permeate through the endosperm and embryo efficiently at the stages before testa rupture. The Arabidopsis testa also limited efficient entry of methoxyfenozide, a chemical ligand that was used for inducible gene expression experiments, into seeds. While the detection of a reporter gene at the early imbibitional stages could be replaced by reverse transcription-polymerase chain reaction (RT-PCR), the interference of entry of the chemical ligand into seeds by the testa was still problematic to gene induction experiments. To develop an efficient inducible expression system for gene function analysis in seeds, an inducible expression system with nitrate, which is a testa-permeable ligand, was examined. The vector containing the 2.1-kb upstream sequence of NITRITE REDUCTASE 1 was able to cause expression of a test gene (long non-coding RNA) in imbibed seeds at the stage before testa rupture in a nitrate-dependent manner. This system can be used not only for characterization of genes associated with seed dormancy and germination in basic research, but also for the development of germination recovery or enhancement technologies for agricultural applications.