Cc. Baskin et al., GERMINATION ECOLOGY OF LEPTOCHLOA-PANICOIDES, A SUMMER ANNUAL GRASS OF SEASONALLY DEWATERED MUDFLATS, Acta oecologica, 14(5), 1993, pp. 693-704
Leptochloa panicoides is one of many summer annuals that grows on mudf
lats formed when water levels in Lake Barkley, an impoundment on the C
umberland River in western middle Tennessee and western central Kentuc
ky, USA, are lowered in late summer-autumn. Seeds were dormant at matu
rity in autumn, and dormancy break occurred over a range of temperatur
es (5, 15/6, 20/10, 25/15 and 30/15-degrees-C), with 30/15-degrees-C b
eing optimal. Seeds required light for germination. Seeds were buried
in flooded and nonflooded soil in October and exposed to natural seaso
nal temperature changes. Seeds reach minimal dormancy (i. e., germinat
ed over the widest range of temperatures) by the following June or Jul
y. Some dormancy loss occurred during winter, but the remainder took p
lace as temperatures increased from February through May or June. Afte
r the initial (primary) dormancy was broken, exhumed seeds germinated
to 80-100 % at 35/20-degrees-C and to 45-100 % at 30/15-degrees-C in a
ll seasons of the year, while germination at 25/15-degrees-C reached a
maximum (20-100 %) in summer and a minimum (0 %) in winter. Thus, see
ds exhibited an annual nondormancy/conditional dormancy cycle. The tem
peratures required for germination of nondormant seeds overlap with th
ose in the habitat from mid-May to mid- to late September. Consequentl
y, seeds can germinate at any time during summer, whenever water level
s drop and the mud is exposed.