PARENT SESSION
Poster Session #49: Reproductive Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
112
Germination responses of dimorphic seeds of Halopyrum mucronatum.
Khan, M. Ajmal1,2, Ungar, Irwin1, 1 2
ABSTRACT- Halopyrum mucronatum is a coastal dune grass that produces seeds twice during each growing season. Seeds produced during May (summer seed) were black and heavier in comparison to brown seeds (winter seed) that were produced in November. There was greater than 95% germination in both seed morphs in non-saline controls at all temperature regimes. Summer seeds were more tolerant to salt at the germination stage than were winter seeds. Germination was more inhibited by low than high temperatures in the salinity treatments. Highest germination was obtained in all salinity treatments at a 20/30 oC (12h-night/12h- day) temperature regime for the winter seeds and at 25/35 oC for the summer seeds. Gibberellic acid, thiourea and nitrate partially alleviated the inhibitory effects of salinity in summer seeds and gibberellic acid, kinetin, and betaine were able to alleviate the effects of salinity on the germination of winter seeds. Our data indicate that seeds of Halopyrum mucronatum exhibited both morphological and physiological polymorphism, which provided them with multiple opportunities to germinate and establish in the hot, dry, saline and unpredictable maritime coastal dune environment along the Arabian Sea coast of Karachi, Pakistan.
KEY WORDS: dormancy, salt tolerance, seed dimorphism