FEATHER INDUCTION BY GROWTH REGULATORS ON MAIDEN TREES OF APPLE AND PEAR
Bioassays of extracts from the upper part of maiden trees of 'Jonathan' (which tends to feather naturally) showed that the "promotor" level decreased during the period of the summer bud break, while the "inhibitor" level appeared to be small but constant. On 'R. I. Greening' (which does not feather easily) the levels of both promoters and inhibitors were higher and constant during the five weeks of the investigation. In 'Golden Delicious' and 'Starking Delicious' apples, and 'Comice' and 'Passe Crassane' pears, a large number of feathers, without any phytotoxic symptoms, were obtained by the use in the nursery of diphenylurea (DPU) at 500 and 1000 ppm and maleic hydrazide (MH) at 1300 ppm. These results afford a possible approach for preparing nursery trees suitable for the improvement of the two modern training systems "sprint palmette" and "slender spindle".
Baldini, E., Sansavini, S. and Zocca, A. (1973). FEATHER INDUCTION BY GROWTH REGULATORS ON MAIDEN TREES OF APPLE AND PEAR. Acta Hortic. 34, 117-122