PLANT PHYSIOLOGY , Vol 114, Issue 2 557-564, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Pollination Increases Gibberellin Levels in Developing Ovaries of Seeded Varieties of Citrus
W. Ben-Cheikh, J. Perez-Botella, F. R. Tadeo, M. Talon and E. Primo-Millo
Department of Citriculture, Instituto Valenciano de Investigaciones Agrarias, Moncada E-46113, Valencia, Spain
Reproductive and vegetative tissues of the seeded Pineapple cultivars of
sweet orange (Citrus sinensis L.) contained the following C-13 hydroxylated
gibberellins (GAs): GA53, GA17, GA19, GA20, GA1, GA29, and GA8, as well as
GA97, 3-epi-GA1, and several uncharacterized GAs. The inclusion of
3-epi-GA1 as an endogenous substance was based on measurements of the
isomerization rates of previously added [2H2]GA1. Pollination enhanced
amounts of GA19, GA20, GA29, and GA8 in developing ovaries. Levels of GA1
increased from 5.0 to 9.5 ng/g dry weight during anthesis and were reduced
thereafter. The amount of GA in mature pollen was very low. Emasculation
reduced GA levels and caused a rapid 100% ovary abscission. This effect was
partially counteracted by either pollination or application of GA3. In
pollinated ovaries, repeated paclobutrazol applications decreased the
amount of GA and increased ovary abscission, although the pattern of
continuous decline was different from the sudden abscission induced by
emasculation. The above results indicate that, in citrus, pollination
increases GA levels and reduces ovary abscission and that the presence of
exogenous GA3 in unpollinated ovaries also suppresses abscission. Evidence
is also presented that pollination and GAs do not, as is generally assumed,
suppress ovary abscission through the reactivation of cell division.
