International Symposium on
Drylands Ecology and Human Security
Salinity, Temperature and Light Affects Seed Germination of Haloxylon salicornicum: a Common Plant in Sandy Habitats of Arabian Deserts
Ali El-Keblawy1 and Nasreen Hassan2
Sand dunes and sand flats represent about 74% of the total area of the UAE. They are under increasing pressures as a result of several developmental activities, accelerated soil erosion, repeated drought and overgrazing. Haloxylon salicornicum (synonymous: Hammada elegans; rimth in Arabic) is one of the most common plant species in sandy habitats. It is a palatable plant and has the ability to resist overgrazing. This species has been considered as one of the most promising species for reseeding deteriorating desert range vegetation and for sand dune fixation. One important step in the way toward using a plant species in reseeding an area is to understand its germination, which is the most critical stage in the life cycle of plants. The aim of the present study was to evaluate the impacts of light, temperature and salinity on germination behavior of H. salicornicum.
Seeds of H. salicornicum were collected from a big population on sand dunes near Al-Ain, UAE. Fresh seeds were sowed in nine levels of salinities (0, 100, 200, 300, 400, 500, 600, 700 and 800 mM NaCl) and then incubated in four incubators adjusted at 15, 20, 25 and 35 oC in continuous light. The effect of light was assessed for non-saline treated seeds (0 mM NaCl) at the different temperatures by germinating seeds both in continuous dark and light. The results showed that the highest germination in both light and dark was at 15 oC and 20 oC and the lowest was at 35 oC. Overall germination in light was significantly greater than in dark, so the difference was significant only at 25 oC. About 60 -80 % of the seeds germinated in salinities up to 400 mM NaCl and 11.7% and 4.3% germinated in 700 and 800 mM NaCl, respectively. This indicates that this species is greatly tolerant to salinity during germination. The best possible germination at higher salinities (500 – 700 mM NaCl) was recorded at 20 or 25 oC. This would enable the seeds to germinate in salty habitats following rainfall of winter months.
A considerable proportion of non-germinated seeds at higher salinities recovered their germination after their transfer to distilled water. This result indicates the ability of H. salicornicum seeds to maintain their viability during exposure to hyper-saline conditions and that the effect of NaCl is more likely to be a reversible osmotic inhibition of germination, rather than ion specific toxicity. Germination recovery was highest at 15 or 20 oC and lowest at 35 oC. Such response could be an adaptation to the desert environment as it would enable the seeds of salty habitats to recover their germination following rainfalls of cold months of winter. In order to use H. salicornicum in restoring deteriorating desert range vegetation our study recommends dispersing the seeds during winter. At this time, the lower temperature and greater rainfall will help seeds of H. salicornicum to germinate in non-saline sand dunes and to recover their germination in the salty habitats.