1996 Volume 65 Issue 2 Pages 237-243
The endogenous levels of abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellins (GAs) in reproductive organs of satsuma mandarin (Citrus unshiu Marc. cv. Ozaki) were determined by gas chromatograph (GC)-electron capture detector, GC-mass spectrometry-selective ion monitoring and dwarf rice bioassay. Their probable roles are discussed.
1. As anthesis approached, IAA concentration in styles and stamens did not change, while ABA concentration of styles increased six-fold. Until 39 days after flowering (DAF), the fresh weigth of fruitlets increased dramatically, while that of 'sepals' which included floral disks, sepals and receptacles increased a little.
2. Fruitlets attained their maximum concentration of ABA 4 DAF and then declined rapidly. Its level remained much lower than that of 'sepals' from 7 DAF. IAA concentrations of fruitlets reached a maximum 7 DAF, and thereafter decrease; that in the 'sepals' increased from anthesis to 31 DAF surpassing that of fruitlets about 15 DAF.
3. GAs concentrations of fruitlets continued to increase from 7 to 31 DAF, and decreased sharply 39 DAF.
4. Because there was a sequence of peaks of endogenous ABA, IAA and GAs levels in fruitlets, it seemed that these hormones may play a sequential and synergistic role in the retention and growth of fruitlets.