APPLE FRUITLET ABSCISSION IS INFLUENCED BY ASSIMILATE SUPPLY

Fruit CO₂ exchange during the fruit setting period was evaluated on mature ‘Jonagold’ apple trees after 4 days of artificial shading, which reduced photosynthetic photon flux (PPF) 90%, followed immediately by application of NAA (15 ppm) and BA (50 ppm). Shading accelerated fruitlet abscission very quickly and reduced dark respiration rate (R_d) and gross assimilation rate (A_g) of fruitlets 3 days after shade removal.
Similarly, a reduced R_d and less negative net CO₂ assimilation rate (A) were recorded in fruitlets 7 days after NAA and BA application.
This indicates that fruit metabolism was reduced starting with abscission.
Following the period of abscission, fruitlets from shaded trees had a higher R_d and a more negative A on the 7^th and 8^th days after the end of shading.
Ethylene evolution was enhanced on the 2^nd and 7^th day after NAA application.
BA enhanced ethylene evolution on the 2^nd day after spraying, but reduced it on the 7^th day.
Ethylene production by persisting fruitlets was enhanced 7 days after shading.

International Symposium on Growth and Development of Fruit Crops

M. Stopar, A. Gregor, F. Bati

NAA, naphthaleneacetic acid, BA. 6-benzyladenine, abscission, assimilation, fruit set, shading, ethylene, Malus domestica

https://doi.org/10.17660/ActaHortic.2000.527.20