Sex determination in dioecious species of plants

Abstract

The review deals with the previous and present data on sexchromosomal mechanisms in the plant system ranging from Bryophytes to Angiosperms. Despite widespread unisexuality, only a few species have well defined heteromorphic chromosomes, heterogamety being present either on the male or on the female side. Reversion of sex through chemical treatment in unisexual species with homomorphic chromosomes indicates a delicate balance between sex determining genes and physiological set up in such species. In heteromorphic types, in majority of cases, Y is generally longer than X and the male tendency of Y is stronger than the female tendency of X. Even though heterochromaticity is associated, the amount of DNA may or not differ in two sexes. Sex chromosomes may often be nucleolar. With the gradual polyploidization or aneuploidy, there is often changeing sexuality indicating distinct sex‐chromosomeautosomal balance for sex determination. Evidences suggest that the change from bisexuality to unisexuality and homomorphicity to heteromorphicity in chromosomes had been a short step in evolution possibly occurring in the recent past. The potential, of banding technique and X‐ray fragmentation, in locating specific sex determining segments, has been indicated.