Effect of dormancy breaking treatments and salinity on seed germination of two desert shrubs

Hammada ( Hammada salicornica Bge) and calligonum (Calligonum intertextum Rech) are dominant shrubs of sandy desert areas of Khuzestan province, in the southwest of Iran, and they are used for sand dune establishment. Seeds of these two species were collected from the wild and subjected to different dormancy breaking treatments ( scarification, sulfuric acid, potassium nitrate solution, rinsing and soaking, and controlled temperatures), and to various salinity regimes. Scarification increased the hammada seed germination percentage, decreased germination time, and the rate of germination was significantly lower under saline conditions. The best dormancy breaking treatment for calligonum seeds was stratification at 10 degrees C for 50 days. The optimum temperature for seed germination was 20 and 15 degrees C for hammada and calligonum, respectively. Cold stratified seeds of calligonum germinated to significantly higher percentages than scarified seeds. The highest germination percentage and plumule and radicle lengths of calligonum were obtained at 10 to 15 degrees C. The germination percentage of scarified/stratified seeds of calligonum were lower than nonscarified/nonstratified seeds. Seed dormancy of both species is likely due to have a physiological effect. Seed germination was not affected by salinity up to 5 and 6 dS/m for either species; however, the germination percentage decreased and the time to germination increased with an increase in salinity. Radicle growth decreased more than plumule growth with an increase in salinity in both species.