Eco-physiological studies on desert plants: germination of Halothamnus iraqensis Botsch. seeds under different conditions

With the aim to investigate if the halophyte Halothamnus iraqensis Botsch. can be suitable for re-vegetation and remediation of salt-affected lands, this study evaluated(1) the effects of photoperiod, thermoperiod, storage period and wings' presence on its seed germination, and(2) the ability of its seeds to have successful germination recovery after salt stress. Germination tests in different photoperiods(12 h light/12 h darkness and total darkness) and thermoperiods(15℃/20℃ and 20℃/25℃) were conducted for seeds collected in 2012, 2013, 2014, 2015 and 2016. The seeds collected in 2016 were sown under different salinity levels(0, 100, 200, 400 and 600 m M Na Cl) to assess the salinity tolerance during the germination. Wings' presence highly inhibited seed germination of this species in both photoperiods and thermoperiods under all salinity level treatments. In addition, the germination recovery occurred well when seeds were deprived of their wings. The photoperiod of 12 h light/12 h darkness and the thermoperiod of 15℃/20℃ were the best conditions for seed germination. Germination percentages of H. iraqensis seeds decreased with the increasing storage duration, especially after three years of the collection. In addition, H. iraqensis seeds were able to germinate under different salinity levels, and their germination percentages decreased with increasing salinity levels. H. iraqensis seeds have the ability to recover their germination after alleviating the salt stress, irrespective of photoperiod, highlighting the halophilous character of this species.

Evaluating germinability of eight desert halophytes under long-term seed storage: Implications for conservation

Ex situ conservation in seed banks is a potential complementary conservation strategy for native plant species.It is well established that ex situ seed banking of native wild plants prolongs seed viability and thereby preserves genetic and species diversity for future use.We evaluated ex situ storage potential of eight halophytic species from deserts in the United Arab Emirates(UAE)by studying seed germination.Specifically,we examined the germinability of freshly collected seeds and seeds stored for three years in a seed bank.We also examined the effect of light conditions on fresh and stored seed germination.Fresh seeds of seven of the eight species tested had a higher germination rates under 12/12 h light/dark fluctuations than did those exposed to total darkness.Storage reduced light sensitivity in Halocnemum strobilaceum,Suaeda aegyptiaca,Salsola drummondii and Salsola imbricata,but increased the requirement for light in Arthrocnemum macrostachyum.In Anabasis setifera,storage decreased germination percentage when there was a 12-hour light/dark fluctuation,but increased germination rate when exposed to the dark treatment.Storage significantly reduced germination in both the light/dark and dark treatments in Suaeda vermiculata and S.aegyptiaca.Germination speed also responded differently to storage;whereas Timson's index significantly increased in A.macrostachyum and H.strobilaceum,it significantly decreased for S.drummondii,S.aegyptiaca and S.vermiculata.Germination of these species at a range of temperatures requires further testing;additionally,we strongly suggest that these laboratory findings be complemented by field studies.

Influence of aerial seed banks on germination response in three desert plant species

Aims To determine if the germination response of desert plant species to a period of aerial storage in field conditions(i.e.mature seeds that remain attached to the parent plant)is comparable to seeds harvested at maturity and stored in ambient laboratory conditions,to better understand the role of aerial seed bank in the germina-tion ecology of desert plants,using one annual and two perennial species.Methods Seeds of three desert plants(Anastatica hierochuntica,Blepharis ciliaris and Scrophularia deserti)that matured in June 2014,were collected from wild plants in June and November 2014,and ger-minated under two photoperiods(0,12 hours light)and three ther-moperiods(night/day temperatures of 15/25,20/30 and 25/35°c).Important Findings Seeds of B.ciliaris and S.deserti had significantly higher germination percentages when harvested and stored for five months,compared to being stored in the aerial seed bank.Germination percentages of these two species increased with decreasing temperature and in the presence of light.These results indicate that these species use a com-bination of aerial and soil seed banks to maintain a percentage of viable seeds through favourable germination periods.Germination percentages of A.hierochuntica were high under all tested circum-stances,indicating that this species relies mainly on the aerial seed bank to maintain a percentage of viable seeds through favourable germination periods.This study shows that the population survival strategies of an aerial seed bank are species-specific.These results have practical implications for conservation and habitat restoration for these species,and also for their propagation since early collec-tion of mature fruits and ex situ storage will result in greater germi-nation percentages of some species.