Comparative germination of Tamarix ramosissima spring and summer seeds

Tamarix ramosissima has bi-seasonal flowering and fruit-setting characteristics. This study compared the morphology and germination characteristics of seeds from Tamarix ramosissima plants during the spring flowering period and the summer flowering period. The results are as follows: there is no significant difference in morphology, such as size and thousand-seed weight, between seeds from different the spring and summer flowering periods. Freshly harvested spring and summer flowering period seeds can both rapidly germinate under the 5/15 °C, 5/25 °C, 15/25 °C or 25/35 °C thermoperiods. Average germination time of the spring flowering period seeds is shorter than that of the summer flowering period seeds, with a TG50 of 2-18 hours (TG50 = the time when germinate percentage reached 50 %). NaCl solutions at concentrations below 0.2 mol/L have no significant effect on the germination of Tamarix ramosissima seeds from either flowering periods. However, at above 0.4 mol/L, higher NaCl concentrations adversely affect the Tamarix ramosissima seeds' germination rates. Seeds from the summer flowering period have higher tolerance of NaCl solutions than seeds from the spring flowering period. Seeds that were incubated in NaCl solution for 8 days cannot recover after being transferred to distilled water (0 % recovery), indicating that NaCl treated seeds permanently lost their germination capability. After storing in room temperature for 2 months, Tamarix ramosissima seeds from both spring and summer flowering periods maintain above 80 % viability. After 2 months, the seed viabilities decrease as the storage time lengthens. The viabilities of seeds from both spring and summer flowering periods decrease to about 40-50 % after storage for 6 months. This study can provide scientific basis for rational utilization of the biological resources in arid desert ecosystems.