Salinity, temperature and light affect seed germination of Haloxylon salicornicum, a common perennial shrub of the Arabian deserts

摘要

Haloxylon salicornicum (Moq.) Bunge ex Boiss. has been considered as one of the most promising species for re-seeding deteriorating desert range vegetation, and for sand dune fixation in the Arabian deserts. However, plant communities dominated by this species have become seriously degraded due to overgrazing. Reseeding degraded communities with this species requires information about light and temperature requirements and salinity tolerance at different temperatures of its seed germination. Seeds were germinated in saline concentrations (up to 800 mM NaCl) in incubators adjusted to 15, 20, 25 and 30 deg C, in both continuous light and dark. In non-saline treated seeds, germination in light conditions was similar for temperatures up to 25 deg C, butdeclined significantly at 30 deg C. Germination in darkness at either 15 or 20 deg C was significantly greater than at 25 and 30 deg C. Both final germination percentage and germination rate decreased as salinity increased. In higher salinity levels (500 - 700 mM), germination at moderate temperatures was greater than at both lower and higher temperatures. Recovery germination decreased as temperature increased. The lower salinity tolerance during germination in H. salicornicum at 15 deg C was attributed to reversible osmotic effect, but lower salinity tolerance at 30 deg C was attributed to Na~+ toxicity that usually causes irreversible damage.