In the case of naturally occurring seedless fruits such as pineapples and bananas : from which part of the flower do these fruits develop and where are the seeds found on the plant? ( e.g above or below the fruit)
Are there seedless true fruits and seedless false fruits?
Are there any artifically produced seedless fruits other than grapes and satsumas?
Neither domestic bananas nor pineapples are "naturally occurring fruits". They would die out without human help.
BANANAS are plants that are originally native to the Malesian Floral Region (Malaysia, Indonesia and Papua New Guinea, etc.). There are two wild ancestors of most bananas Musa acuminata (the A genome) and Musa balbisiana (B genome). Most modern cultivars (there are hundreds) are polyploids of one or the other or both these founding species. Wild bananas (2n = 22) are pollinated by bats, and are easily able to produce little round black seeds, and do not produce large fruits.
A triploid hybrid arises most commonly by what is called meiotic restitution, where a female egg as a result of faulty meiotic division is diploid, and is pollinated by a haploid pollen nucleus, the resulting nucleus and seed becomes triploid (3n=33) . This odd number of chromosomes makes subsequent meiotic division in the next generation chaotic and less successful, thus commonly making such a hybrid sterile. A wild Musa acuminata might therefore be AA in genome and a triploid of this species AAA. Many banana hybrids have formed in the past. Polyploid bananas are now of such constitution as AAB, AAAA, and ABBB.
The banana fruit is an inferor ovary (like that of a marrow). How do we get a fat juicy seedless modern banana fruit? Many plants (including wild bananas) show parthenocarpy (producing a fruit without seeds). As polyploids are also larger and more vigorous what humans have done (over thousands of years) is to select from polyploids for seedless, parthenocarpic, large, nutritious fruits and have propagated these bananas exclusively vegetatively for generations. It is a seedless 'true fruit' therefore.
PINEAPPLES are all of one species Ananas comosus. This is another ancient cultivar like the banana. Here, however, the hybrids of wild species, in the Paraguay/Panama region of South America, were artificially selected by Tupi-Guarani Indians a few thousands of years ago. The wild species exist still in the forest and are humming-bird pollinated and produce thousands of tiny seeds. By the time of Columbus the one sterile hybrid species, Ananas comosus, was found throughout much of central and south America and was entirely vegetatively grown.
What is a pineapple? The pineapple plant has an inflorescence, a flowering spike, like a common plantain, with a tuft of normal leaves on top. All of the 200 flowers around the spike develop parthenocarpically (no seeds) and their fruits (developed from the female ovary) fuse together and join up into one (syncarpic) fruit. It is not a false fruit. Pineapples take at least two years to grow. They are propagated from suckers or even from pineapple tops.
"False fruits" are fruits like strawberries, where the fleshy part is not from the ovary but is formed from the flower receptacle. Strawberries are all 'seeded' as far as I know!
Examples of other seedless fruits (beside bananas, pineapples, citrus fruits and grapes) might be melons, breadfuit and custard apples! I do not know of any other temperate examples except perhaps some varieties of cherries. Many 'seedless' fruits have been de-seeded e.g. seedless olives. These two ideas should not be confused.
Stephen Tomkins
