A COMPARATIVE-STUDY OF THE SEED-GERMINATION BIOLOGY OF A NARROW ENDEMIC AND 2 GEOGRAPHICALLY-WIDESPREAD SPECIES OF SOLIDAGO (ASTERACEAE) .4. ROLE OF SOIL-MOISTURE IN REGULATING GERMINATION

Seeds of the narrow-endemic Solidago shortii and of the geographically -widespread S. altissima and S. nemoralis buried in December 1993 were exhumed in June 1995 and given 10 cycles of 1 day wet/5 days dry, 9 o f 2/5, 8 of 3/5, 7 of 4/5 and 6 of 5/5 in light at 30/15 degrees C; th e control was kept continuously wet during the experiment. Seeds of th e three species incubated on wet substrate for 3, 4 or 5 days germinat ed to greater than or equal to 47% during the first cycle. On the othe r hand, seeds kept moist 2 days germinated to only 4-26% in the first cycle, and none kept moist for 1 day germinated. Cumulative germinatio n percentages of seeds of all three species at the end of the final cy cle of the 1/5 treatment were 0-4%. In the 2/5 treatment, cumulative g ermination percentages of S. altissima and S. shortii seeds at the end of the final cycle were 50 and 41%, respectively, but that of S. nemo ralis was only 4%. For all three species, cumulative germination perce ntages were greater than or equal to 55% at the end of the final cycle of the 3/5, 4/5 and 5/5 treatments. Control seeds of the three specie s germinated to 85-99% after 2 weeks, and no additional seeds germinat ed during the remainder of the experiment. High percentages of seeds w ere viable in the treatments and control at the end of the experiment; however, some seeds of S. nemoralis and S. shortii given 1/5, 2/5 and 3/5 treatments became dormant. The ecological implication of this stu dy is that seeds of the three species will not germinate on the soil s urface after brief rainfall events in summer. The germination response of the narrow endemic is similar to that of its two geographically-wi despread congeners.