Lupine (Lupinus polyphyllus) Flower in Response to Long-day Photoperiod by Day Extension

Abstract

Ninety-six uniform plants of each `Russell hybrid' and `Gallery' mix lupines sown 9 June 1995 were randomly assigned to 32 unique treatment combinations. On 14 Dec 1995, plants were either placed in a 17/13°C day/night temperature (DT/NT) greenhouse (COOL) or 22/18°C DT/NT greenhouse (WARM) as controls, or in a constant 4.5°C cooler in the dark for 6, 8 10, or 12 weeks. After cooling, plants were transplanted to #1 nursery cans (2.75 liter) using Sunshine mix #2 and were assigned randomly to the COOL or WARM greenhouse. Greenhouse control plants under natural days were transplanted at intervals similar to cooled plants. Days until visible bud and flowering were analyzed using SAS PROC GLM. Plants receiving long day (LD) flowered 7 to 10 weeks (46 to 70 days) after the start of LD forcing. Buds were visible in 30 to 35 days. Plants receiving natural days (ND) did not flower uniformly unless they were cooled for 12 weeks, yet flowering took longer (8 to 12 weeks) when compared with LD. Unfortunately, LD lighting for the entire forcing period caused excess stretching, so plants finished too tall for quality potted plants. Forcing in a COOL greenhouse delayed flowering about a week compared to the WARM greenhouse.