IDENTIFICATION OF PLANT HORMONES IN ENDOSPERM LIQUID OF MANGOSTEEN FRUITS AT YOUNG DEVELOPMENTAL STAGES

Mangosteen, known as the queen of tropical fruits, has a unique sexual reproductive feature; that is, it can produce seeds without fertilization by apomixis. Interestingly, all seeds in mangosteen fruit are produced by apomixis, since the mangosteen tree is dioecious and no male trees have been found. As mangosteen is mainly propagated by seeds, all mangosteen trees are thought to be a single clone. Usually, mangosteen fruit have 4-7 locules, but only 1-3 seeds will develop by apomixis in a fruit. According to our previous morphogenetic observation, apomictic seeds appear as the cell mass at early stages of fruit development after a protuberance is derived from outgrowth of the integument cells in the well-developed locule. This well-developed locule contains liquid endosperm, while the poor-developed and deflated locule contains almost no liquid endosperm. We speculated a role of this endosperm liquid on development of apomictic seed, and assumed the existence of plant hormones in the liquid. So, we attempted to identify plant hormones, especially IAA, by using a gas chromatography-mass spectrometry with an internal standard of its deuterium compound, and have identified the existence of IAA in the liquid of well-developed locules at the young stage of fruit development (6 weeks after anthesis). In addition, we detected small amounts of cis,trans-ABA, and jasmonic acid with trace amount in the same analysis. These results are coincident with our preliminary experiment for analyzing endosperm liquid of mangosteen fruit.