Michigan State University-Department of Energy Plant Research Laboratory, East Lansing, Michigan 48824.
Plant Physiol. 1992 Aug;99(4):1575-81. doi: 10.1104/pp.99.4.1575.
Satsuma (Citrus unshiu [Mak] Marc.) and Clementine (Citrus reticulata [Hort.] Ex. Tanaka, cv Oroval) are two species of seedless mandarins differing in their tendency to develop parthenocarpic fruits. Satsuma is a male-sterile cultivar that shows a high degree of natural parthenocarpy and a high fruit set. Seedless Clementine varieties are self-incompatible, and in the absence of cross-pollination show a very low ability to set fruit. The gibberellins (GAs) GA53, putative 17-OH-GA(53), GA(44), GA(17), GA(19), GA(20), GA(29), GA(1), 3-epi-GA(1), GA(8), GA(24), GA(9), and GA(4) have been identified from developing fruits of both species by full-scan combined gas chromatography-mass spectrometry. Using selected ion monitoring with [(2)H(2)]- and [(13)C]-labeled internal standards, the levels of GA(53), GA(44), GA(19), GA(20), GA(1), GA(8), GA(4), and GA(9) were determined in developing ovaries at anthesis and 7 days before and after anthesis, from both species. Except for GA8, levels of the 13-hydroxy-GAs were higher in Satsuma than in Clementine, and these differences were more prominent for developing young fruits. At petal fall, Satsuma had, on a nanograms per gram dry weight basis, higher levels of GA(53) (10.4x), GA(44) (13.9x), GA(19) (3.0x), GA(20) (11.2x), and GA(1) (2.0x). By contrast, levels of GA(8) were always higher in Clementine, whereas levels of GA(4) did not differ greatly. Levels of GA(9) were very low in both species. At petal fall, fruitlets of Satsuma and Clementine contained 65 and 13 picograms of GA(1), respectively. At this time, the application of 25 micrograms of paclobutrazol to fruits increased fruit abscission in both varieties. This effect was reversed by the simultaneous applications of 1 microgram of GA(3). GA(3) alone improved the set in Clementine (13x), but had little influence on Satsuma. Thus, seedless fruits of the self-incompatible Clementine mandarin may not have adequate GA levels for fruit set. Collectively, these results suggest that endogenous GA content in developing ovaries is the limiting factor controlling the parthenocarpic development of the fruits.
温州蜜柑（Citrus unshiu [Mak] Marc.）和克莱门氏小柑橘（Citrus reticulata [Hort.] Ex. Tanaka，cv Oroval）是两种无核蜜柑，其产生无核果实的倾向不同。温州蜜柑是雄性不育品种，表现出高度的自然单性结实和高坐果率。无核克莱门氏小柑橘品种是自交不亲和的，如果没有异花授粉，其结实能力非常低。通过全扫描组合气相色谱-质谱法，从这两种物种的发育果实中鉴定出了赤霉素（GAs）GA53、假定的 17-OH-GA（53）、GA（44）、GA（17）、GA（19）、GA（20）、GA（29）、GA（1）、3-epi-GA（1）、GA（8）、GA（24）、GA（9）和 GA（4）。使用带有 [(2)H(2)]-和 [(13)C]-标记内部标准的选择离子监测，测定了开花前和开花后 7 天的发育卵巢中 GA（53）、GA（44）、GA（19）、GA（20）、GA（1）、GA（8）、GA（4）和 GA（9）的水平，来自这两个物种。除了 GA8 之外，13-羟基-GAs 在温州蜜柑中的水平高于克莱门氏小柑橘，并且这些差异在发育的幼果中更为明显。在花瓣落下时，温州蜜柑的 GA（53）（10.4x）、GA（44）（13.9x）、GA（19）（3.0x）、GA（20）（11.2x）和 GA（1）（2.0x）的水平更高。相比之下，GA（8）的水平总是在克莱门氏小柑橘中更高，而 GA（4）的水平差异不大。GA（9）的水平在这两个物种中都非常低。在花瓣落下时，温州蜜柑和克莱门氏小柑橘的果小核中分别含有 65 和 13 皮克的 GA（1）。此时，将 25 微克的多效唑施用于果实会增加两个品种的果实脱落。同时施用 1 微克的 GA（3）可以逆转这种效果。GA（3）单独使用可以提高克莱门氏小柑橘的结实率（13 倍），但对温州蜜柑影响不大。因此，自交不亲和的克莱门氏小柑橘无核果实的果实结实可能没有足够的 GA 水平。综上所述，这些结果表明，发育卵巢中的内源 GA 含量是控制果实单性结实发育的限制因素。
