Average Daily Temperature and Reversed Day/Night Temperature Regulate Vegetative and Reproductive Responses of a Doritis pulcherrima Lindley Hybrid

Abstract

Listen

Translate article

It was unknown how prolonged periods of cool days and warm nights affect Phalaenopsis Blume hybrids, which perform crassulacean acid metabolism and absorb CO2 primarily at night. The ‘Lava Glow’ plants vegetatively propagated from a hybrid Doritaenopsis (Phalaenopsis Buddha's Treasure × Doritis pulcherrima Lindley*), 15 cm in leaf span, were grown at day/night (12 hours each daily) temperatures of 30/25, 25/30, 25/20, or 20/25 °C under 170 μmol·m−2·s−1 PPF. After 37 weeks, plants at the higher average daily temperature of 27.5 °C (ADT, 30/25 and 25/30 °C) produced more leaves than the lower 22.5 °C ADT. Those grown at 30/25 °C had the largest leaf span and combined length of the new leaves. Plants at 30/25, 25/30, 25/20, or 20/25 °C had 5.0, 4.7, 3.6, and 2.8 new leaves that were 72, 61, 44, and 29 cm in total length, respectively. Warmer nights than days resulted in a small leaf span, reduced leaf growth, and shorter leaves that were particularly noticeable at the 22.5 °C compared with 27.5 °C ADT. Leaves that emerged and grew at the lower ADT had a reduced length to width ratio and a more oval shape. The most striking effect of the 20/25 °C treatment was that 14 of 15 plants bloomed, whereas only five plants at 25/20 °C and none at 30/25 or 25/30 °C produced flowers. Similar results were obtained in a second experiment using 30/20, 20/30, 25/15, or 15/25 °C. After 29 weeks, all plants at 15/25 °C bloomed, whereas none in the other treatments had flowers. Long-term exposure to 15/25 °C resulted in slow leaf production and undesirable small leaves. These results suggest that day and night temperature may both affect growth and flowering of this orchid.