Hi Natalie. Since you aren't getting much response...I will attempt to try. Have you ever had a 'seedless' watermelon, before? It works on a somewhat similar priinciple.. Except that sort of watermelon is a fruit, but it does need pollen exposure, on the female flower, yet only for it to produce the melon.
I suppose the flowers last longer in these varieties. Some flowering plants are hybridized to produce results they want, but that are sterile, & can be parthenocarpic, like most bananas (have no seed) . That s to say, with with those sort of sunflowers, they produce a hybrid seed/seeds but the progeny only need exposure to pollen, yet there isn't any actual pollination/fertilization, which is normally required for viable seed to occur.
Chromosome numbers & genetics can play a role, as can exposure to chemicals (e.g. colchicine, or GA3) as well as self (in)/ compatability. Then you get into topics like 2N, 4n, or diploid & triploid, etc... (Now I wish I had studied in plant Biology!)
So, if a hybridizer wants to cross two different species,with the end results being sterility, they achieved a Sunflower that may last longer, but doesn't cause the unwanted effect of an area beneath, where it makes for other plants more difficult to germinate or grow..... For comparison, a similar process, is even found in animal husbandry, as it can also be accomplished... The name for the sterile result,; is a mule!
I have created sterile hybrid flowers before, but if it isn't perennial, then you have no root to divide to multiply & those sterile annuals just flowers away & then dies, without any seeds, from my observation..
