Methods of Sex Determination in Dioecious Angiospermous Plants

Angiosperms are the most diverse group of land plants which provides fruits, food, seed for cultivation and material for hybridization purpose etc. Approximately 90% of all angiosperm species have hermaphrodite (bisexual) flowers and the remaining, onetenth are either monoecious (male and female flowers are separate but grow in same plant) or dioecious (male and female flower grow on different plant). During evolutionary time the unisexual flowers have arisen from the bisexual ancestral through mutation either causing male sterility or causing female sterility resulting gynodioecious (having female flower on one plant and hermaphrodite flowers on the other plant of the same species) and androdioecious (having male flower on one plant and hermaphrodite flowers on the other plant of the same species) plants. But female-sterile mutation is rare in plants because female function is more valuable in nature (Charlesworth and Charlesworth, 1978). The comparative study on the evolution of dioecious plants support that they has evolved from an ancestral gynodioecious conditions, although there are few reports in which monoecy seems to be ancestral to dioecy. Dioecy possess a barrier to selffertilization, therefore plays a very important role in evolution. The exchange of genetic material between two different individuals leads to new combinations of genes which enable a new plant to easily adapt or survive to a changing environment (Milewicz & Sawicki, 2012). Plants which are fertilized with foreign pollen produce more abundant and healthier offspring than the individuals which are fertilized with own pollen (Malinowski, 1978). This correlation is clearly visible in many dioecious plants e.g. in Cannabis sativa, dioecy contributes to greater yield and produce offspring with more valuable fibre, therefore supports that crossbreeding leads to the production of better offspring (Mandolino et al., 1999).