heres the science (also 2 posts up, lol)

Biology lesson.

also this:
sex is determined by the chromosomes in the sperm that fertilizes the egg.
it is true in some developing animal embryo's, such as a crocodile still in the egg, sex is determined by temperature. this is not true for most dicot plants. temperature does determine a few things that would lead us to believe it controls sex. it is important to note here the base sex of the plant is determined by chromosomes from fertilization.
there are proteins with in a plant that respond to different temps by creating what is called a "second messenger". you need to start thinking on the most basic cellular level. the second messenger is another molecule that travels into the nucleus and causes dna to turn on or off a specific gene set (note: this is not the chromosomal sex dna.) Gibberellic acid is one of the hormones produced from these second messengers changing cell metabolism and dna transcription.

studies have shown that gibberellic acid can fool with the sex of a plant. (but note once again that the original sex was determined at fertilization.) GA has been proven to grow bigger flowers but may also turn a female into a hermie. When GA is applied to a male plant, the male sporangia will grow huge, but no flowers(female) will develop.
this being said, you should be able to deduce that the original female sex can be changed (hermie), but if the original sex is male, the same technique(shifting hormone concentrations) will not "inject" as it were, female chromosomal gene information.

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