ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
EFFECTS OF GA3 ON FRUIT AND SEED DEVELOPMENT OF SELF-STERILE PLUM CULTIVARS |
| Authors: | W. Hartmann, S.F. Anvari |
| Abstract:
Unfavourable weather conditions at flowering-time are one of the reasons for poor cropping of self-sterile plum cultivars. Fruit set of open- and hand-pollinated flowers was essentially higher after treatment with GA3, whereby two applications proved to be more effective than one. A high fruit set in connection with the best fruit size of all treatments we got by spraying GA3 four and six weeks after petal fall. Decreased fruit weight resulted from better cropping, but also from the high percentage of fruits with no or with aborted seeds. GA3 promoted the development of parthenocarpic fruits and prevented the abscission of fruitlets with aborted embryos. The seed content of treated fruits was therefore always lower. In experiments with hand-pollinated flowers we observed that high concentrations of GA3 could also have a direct effect on seed development; so we registrated not only more fruits with no or with aborted seeds, but also fewer fruits with two fully developped seeds. The influence of GA3 on pollen tube growth and on seed development was studied by flourescence microscopy. In all the years we could not observe any effect of GA3 on pollen tube growth, but GA3 enhanced the aging of ovules and retarded the development of the haustorium. The nuclear divisions in the endosperm of fruitlets were retarded after treatment with GA3 and stopped completely when 80–100 free endosperm nuclei were produced. The nuclei were reabsorbed and embryo development was not possible. The worser results with a GA3-treatment at or some days after petal fall than four and six weeks after petal fall is to explain by negative effects on ovules, haustorium, endosperm and embryo development. | |
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