Floral initiation in gooseberry (Ribes uva-crispa L.) and its control by daylength and temperature

The morphogenetic changes of the bud meristem during floral initiation in gooseberry were examined by scanning electron microscopy. Six stages, similar to those reported for black currants, identified. We also studied environmental control shoot growth and cvs. Mucurines, Pax Xenia two experiments daylight phytotron compartments at 12, 18 24°C. Under natural daylength conditions Ås, Norway (69°40’N), started decline mid-August ceased early September. Cessation was associated with 12°C, while 24°C, only ‘Mucurines’ initiated primordia. Floral Stage 2 reached 3 September ‘Xenia’ 12°C nearly weeks later ‘Pax’. In a second experiment controlled photoperiods, all cultivars growing flowering 10-h SD within 2–3 weeks, 20-h LD, continued 8 without initiation. conditions, flowers Flowering performance following spring verified these results. conclude that is an obligatory plant critical photoperiod 15–16 h.