Pitam (Pitom)
An etrog with an intact pitam is considered especially valuable. A pitam is composed of a style (Hebrew: "דַד"), and a stigma (Hebrew: "שׁוֹשַׁנְתָּא"), which usually falls off during the growing process. However, varieties that shed off their pitam during growth are also kosher. When only the stigma breaks off, even post-harvest, it could still be considered kosher as long as part of the style has remained attached. If the whole pitam i.e. the stigma and style, are unnaturally broken off, all the way to the bottom, it is not kosher for the ritual use.
Many pitams are preserved today thanks to an auxin discovered by Dr. Eliezer E. Goldschmidt, formerly professor of horticulture at the Hebrew University. Working with the picloram hormone in a citrus orchard one day, he discovered, to his surprise, that some of the Valencia oranges found nearby had preserved perfect pitams. Usually a citrus fruit, other than an etrog or citron hybrid like the bergamot, does not preserve its pitam. When it occasionally does, it should at least be dry, sunken and very fragile. In this case the pitams were all fresh and healthy just like those of the Moroccan or Greek citron varieties. Experimenting with the picloram in a laboratory, Goldschmidt eventually found the correct “dose” to achieve the desired effect: one droplet of the chemical in three million drops of water. This invention is highly appreciated by the Jewish community.
Read more about this topic: Etrog