| dc.description.abstract | The possible mechanisms of apple fruitlet abscission are presented in this
paper. Prevailing hypothesis on hormonal triggered processes in the event of “correlative
dominance effects” of adjacent fruitlets or nearby shoot tips has the opponent theory of
assimilate supply dependent fruitlet abscission. Assimilation shortage may also be involved in
the correlative auxin processes but the connections of both statements are not clear yet. On
last years a lot of evidence is provided in support of assimilation dependent fruitlet abscission
process. At the time just after the end of the flowering, a strong competition between fruitlets
and shoots for photosynthates exist. Shading experiments comparable for a few days of
cloudy weather provoked strong natural apple fruitlet abscission. If the applications of
chemical thinners are followed by a few days of shading, much stronger abscission occurs
comparing to thinner applications without shade. A photosynthesis inhibitor metamitron has
gone into registration for fruitlet thinning purpose and is available in Europe last year. A good
thinning results can be achieved up to 14 mm king fruit diameter, but additional studies
should be made to adapt dosage for the present and predicted light intensity at the time just
after metamitron application. | sr |
