A MECHANISTIC STUDY ON THE EFFECTS OF PHOTOPERIODIC LIGHTING ON FLOWERING TIME AND FLOWER QUALITY OF 'HUNTING SONG' GLADIOLUS

Three photoperiodic treatments: short day (SD, 11-h PP); long day (LD, 14-h PP); and night interruption (NI) were applied on gladiolus (Gladiolus grandiflorus ‘Hunting Song’) when forcing flower in winter. Flower height was measured every 10-20 days until flowering. Flower quality (flower height, spike length, florets per spike), leaf chlorophyll content and photosynthesis rate, dry weights and mineral (N, P, K, Ca, and Mg) contents of root, bulb, leaf and flower spike were measured at flowering. The treatments had significant effects on flower development and flower quality. These effects are related to, but not necessarily proportional to the amount of DM and minerals accumulated and distributed to the spikes. Plants in SD treatment flowered 100.6 days after planting (DAP). This is significantly earlier than plants in LD (105.1 DAP) and NI (107.0 DAP). SD treatment resulted in the highest DM and mineral contents in spikes while LD treatment resulted in the highest flower, longest spike and the most florets per spike.

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