Educational Questions & Answers

How is sex determined in dioecious plants?

More than 90 per cent of flowering plants produce perfect flowers that have both male and female reproductive organs.

Of the remaining plant species, about half are monoecious, producing male and female flowers on the same plant and the rest are dioeceous, producing male and female flowers on separate plants. Plants have developed weveral interesting mechanisms for determination of sex.

Silene latifolia is the most well studies dioeceous plant for sex determination mechanisms. In this species, sex determination is by sex chromosomes similar to that inmay animals, males are XY and felames are XX.

In male and female plants, female and male reproductive organs do initiate respectively by are aborted early in flower development. The Y- Chromosomes are thought to carry genes that promote male development and suppress female development. A similar mechanism has also been reported in the bryophyte Marchantia.

Papaya can produce male,female and hermaphrodites depending on the genotype of a single sex determining locus. This locus is thought to be clustered with several genes that play a role insex determination.

Cucumber is usually monoecious producing female flowers at the top of the inflorescence ans male flowers at the bottom. It has been found that sex is determined by the concentration gradient of the plant hormone ethylene, which acts to promote female sex.

In maize, agradient of the plant hormone gibberellic acid regulats the emergence of the male and female inflorescences. Hormone gradients in these species are genetically determined by two or three different genetic loci.

IN addition to the above mechanisms, in the fern Ceratopteris, sex determination is epigenetically determined by a pheremone.

All individuals are hermaphrodites ans developed individuals secrete the pheromone so as to masculinise the surronding juvenile plants

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How is sex determined in dioecious plants?