SOURCES OF GENETIC-VARIABILITY IN A NEOTROPICAL CLEISTOGAMOUS SPECIES, RELBUNIUM-HYPOCARPIUM, RUBIACEAE

Twenty-two strains of Relbunium hypocarpium collected from four locali ties in Rio Grande do Sul (Brazil) and one in Argentina were studied f or glutamate oxaloacetate transaminase (GOT, EC 2.6.1.1) isoenzyme pat terns by horizontal gel electrophoresis in order to obtain more precis e data on their reproductive system and on the origin of the Variabili ty observed in this cleistogamous species. The study was conducted on adult F-1 and F-2 of plants from nature, and seedlings of their progen ies. When some variation was observed in the progeny, the same or sib seedlings were also analyzed for isoesterases (EST, EC 3.1.1). The res ults showed that R. hypocarpium, a cleistogamous species, and reproduc es mostly by self-fertilization, although at least one event of cross- fertilization that occurred in nature, was detected in one strain out of 22 An additional source of variability observed in 14% to 18% of th e strains, in the GOT system, was found to be the occurrence of isoenz yme modifiers, possibly involving post-synthesis modifications, the ad aptive significance of which we are not yet able to explain.